Giving Up On Plants; or, When to Commit Plant Murder

Erica1 Comment

I think we’ve all been there. Everything else in the vegetable garden is going well, growing as it should, producing bountifully, getting the better of challenges. And then there’s the one plant that just… isn’t. (Or more than one that just aren’t.) Maybe, though, given a little more time, a little more fertilizer, a little more effort, a little more love… it might pull through? Or is it taking up space for no reason? Worse, is keeping it around bad for your more successful plants?

When, in fact, is it the right time to commit plant murder?

I can’t help joking, but of course we all hate killing plants that we’ve tried hard to nurture, maybe even growing them from a tiny seed. But let’s face it, there’s only so much space in a garden, and the season will be over soon. We don’t want to waste the time and square feet that we have. Most of the plants in an edible garden are annuals, and with these we need to make decisions soon. With perennials, maybe you can wait until next year to see if conditions improve.

How do you figure out when and if you should pull a plant out of the garden? Well, it’s like a detective story in reverse; first, you need to be an investigator, and then a potential killer. Find out what’s wrong with the plant; assess how bad the problem is and what the consequences might be; and then make a decision based on the facts.

The HGIC website is a good place to start. If the plant in question is a vegetable, I suggest starting with the Vegetables Grown in Maryland page, select your vegetable, and visit the “Growing ___ in a Home Garden” article. From there, you can explore the list of potential problems. If you can’t figure it out from there, or from more searching online, you can contact the Ask Extension team, or ask your county’s Master Gardeners.

The problems you might encounter with plants include:

PESTS

Pest problems are often fixable. Follow the advice given at HGIC or on other regional Extension websites, and you are likely to be able to control the pests sufficiently to get a crop. However, there are a few instances where giving up on the plant is a better option.

  • The pest has killed the plant or come close to killing it. For example, squash vine borer can take out a squash plant in days, and if you don’t remove the pest in time, or it has destroyed most of the main stem, you will not be able to revive the plant. Flea beetles can eat most of the foliage of young eggplants, to the point where they can’t survive. But don’t jump to the conclusion that a few holes mean a devastating invasion.
  • The pests keep coming back even when you remove them. This happens often in community garden situations or when you have close neighbors growing the same plants. Maybe you can work together to get rid of the pests, but if that’s not an option, you might consider switching to a less susceptible crop.
  • There is a solution, but you can’t implement it right now. This is particularly true of animal pests—maybe you need to fix a fence or fill a hole, and it’s best done in the off-season. Or you have overplanted a bed, making it difficult to reach plants to remove pests. The easiest fix may be to remove the temptation and limit the pest’s options in the process.
A leaf of a squash plant with holes and yellowing from squash bug feeding.
Squash bug damage in plants I couldn’t get to because I overplanted my small garden. Photo by Erica Smith

Remember that not dealing with insect pests as soon as possible means that they are able to complete their life cycle and make more pests! If you do remove a plant that is infested, try putting it in a black plastic trash bag and leaving it out in the sun until the pests are dead. That way, you haven’t just chased them off to attack another plant. You can then put the bag in the trash or even add the contents to your compost if the plant isn’t also diseased. Speaking of which…

DISEASES

If you suspect a plant disease, diagnose it and read up on its prognosis. Does it kill a plant fast, or is it slow-working? How lethal is it and how fast does it spread? Again, it’s likely you can keep plants going for a while, for example with a common fungal disease like early blight on tomatoes, but there are cases where plant removal is advisable. If you do pull plants, put them in the trash rather than adding the debris to your compost.

  • Diseases that spread quickly. If you see the disease spreading to other plants, and it can’t be stopped by removing affected foliage and other plant parts, you may need to pull the plants that are diseased. This is especially true in truly destructive diseases like late blight (luckily, this is uncommon in Maryland!), but also with more common issues like bacterial leaf spot, which has devastated some of my recent pepper crops. Remember, most diseases are specific to particular species or families, so you don’t need to pull out your whole garden because one type of plant is affected.
  • Diseases that will prevent a plant from producing. Examples include bacterial wilt that kills a cucumber overnight (easy call), or mosaic virus that lets a squash plant continue to grow but will kill it before it has any viable fruit (harder to make the decision to pull). In perennial plants such as fruit trees, you may lose a crop one year but not the next; on the other hand, if the disease comes back for several years running despite treatment, why are you still trying? (It took me a couple years of fire blight on quince to decide I wasn’t meant to grow it.)
  • Multiple factors, including disease. A disease alone might not be enough to make you decide to pull a plant, but if it’s also battling pests or drought, or producing very little for some other reason, it might not be worth keeping.
A red bell pepper with rotten spots on the skin.
This pepper damage was likely caused by bacterial leaf spot. Not worth keeping the plants going if the result looks like this! Photo by Erica Smith

OTHER

  • Failure to thrive. This is a generic term for “just not cutting it”: looking puny and sad. Maybe the seed you grew this plant from was the worst one in the packet; maybe it got stressed from being in a pot too long; maybe the soil conditions in that particular spot are poor; maybe we’ve had crazy weather and the plant just can’t cope. Some TLC and fertilizer may help, but not always.
  • Bolting. Cool-weather crops often last into the summer, but there’s always a point when they want to go to flower, and no amount of pruning will stop it.
  • Failure to produce correctly. Maybe the plant looks healthy but it isn’t making what it’s supposed to make. Root vegetables that don’t make roots; beans that don’t bean; broccoli that won’t head up. A little extra time and some fertilizer may help, but possibly not. Pull the plant; do a soil test and plan an appropriate fertilizer regimen next year; look at conditions generally (enough sun? enough water?).
  • Need the space for something else. In a small garden, we sometimes have to make choices about what hangs in there and what gets ousted. If you want to grow kale and there is nowhere else to put it but where the tomato plant is covered with early blight and producing many fewer fruits, it may be time for the tomato plant to go.
A weak looking pepper plant with only 1 small fruit starting to grow.
This fish pepper has been looking sad all season. Might be a soil issue, or stress due to root crowding in the pot. Or something else. I still don’t want to pull it out, so I gave it some fertilizer and a pep talk. Photo by Erica Smith

In general, remember that failures are a learning experience! Sometimes we learn about a fundamental flaw in our garden or in our practice; sometimes we learn that a particular plant isn’t for us (but give it another try first!); sometimes we can just chalk up failure to a bad year or one fixable mistake. Pulling a plant is also an opportunity to put another plant in its place. (Probably not one of the same species, because the problem may affect it too.) Succession planting is made easier by thoughtful but relatively quick decision-making; get out that sick squash and you may still have time to put some bush beans in, or to get the space ready for fall planting.

And as gardeners, we always continue to hope things will be better next time!

By Erica Smith, Montgomery County Master Gardener. Read more posts by Erica.

Why don’t I see pollinators on my plants?

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One of the most widespread actions implemented to support pollinators and other beneficial organisms is the planting of (native) flowering plants. The idea is that if we offer food to pollinators, they will come. However, we may have planted the plants, but the pollinators still aren’t coming. What could be happening? In this post, I will cover some biological reasons why this may be happening, and some solutions to consider.

Not all flowers are made equal

To a pollinator’s eye, not all flowers are the same. As we mentioned in other posts, each pollinator group (e.g., butterflies, birds, bees, flies…) has a different shape and different sensorial and physical abilities. While a butterfly may be able to reach the nectar at the bottom of a very tubular and long flower, a fly may not. Likewise, a large pollinator that is physically stronger than a small pollinator may be able to enter a very closed flower. Further, a night pollinator can obtain nectar from plants that offer it at night, while it will not get anything from those that offer it during the day…. I guess you see my point. Essentially, pollinators prefer flowers that make it easiest to locate and harvest resources like nectar and pollen. These differences mean that unless those flowers are present in a landscape, certain groups of pollinators may not be seen at all.

A grid of 9 flowers in various shapes and colors and different pollinators from bees and wasps, to moths and birds.
Different floral shapes and colors make floral rewards more easily accessible to different pollinators. Photos: J. of Pollination Ecology.

Not all flowers necessarily offer what a pollinator is after

Pollinators visit flowers to obtain something they need. That something may be food (e.g., nectar, pollen, parts of the flower), materials for reproduction (e.g., perfumes), materials for nest building (e.g., resins, floral oils), or simply a place to overnight, stay warm, and/or mate. As a matter of fact, not every single flower serves all those needs, making the pollinators end up “sorting themselves” among the plants that offer what they need.

A yellow blooming flower cluster with a bee climbing inside one of the blooms.
A bee of the genus Chalepogenus visiting a flower of Calceolaria dentata (native to Chile and Argentina) to collect floral oils and pollen. Photo: A. Espíndola.

Let me give you an example. In my research life, I work on a specialized pollination system that involves flowers that do not offer nectar at all, but instead offer floral oils (and pollen) in exchange for pollination (you can read more about this from the blog post: Why Do Pollinators Visit Flowers?, May ’20). These flowers are called lady slippers and belong to the Pan-American genus Calceolaria. When we observe which pollinators visit the flowers, we see that it is mostly bees who specialize in collecting floral oils (in our case, bees of the genera Centris and Chalepogenus), and basically nothing else. In landscaping, filling our yards with only one specialized flower type drastically limits pollinator diversity. For instance, if we only planted oil-producing flowers, we would not see many diverse pollinators. This highlights a key rule: the rewards a plant offers dictate the visitors it attracts. Just as varied flower shapes are crucial, providing a diverse mix of nutritional rewards—like nectar, pollen, and oils—is the best way to boost the number and variety of pollinators in our green spaces. As for the floral shape I was referring to, planting species that offer different types of rewards is a very good way to increase the number and types of pollinators we see in our green spaces.

The flowers do not necessarily want to share too much

Plants attract pollinators because they can get pollination from them, which allows the plant to reproduce. From a biological point of view, a pollinator will be a good one if it carries pollen from the stamens of a flower and makes it land on the stigma, so it can germinate and then fertilize the ovules. This is all good and nice; the problem, however, is that many pollinators use pollen as food. This creates a conflict between the plant’s and the pollinator’s interests: a plant needs the pollen (that contains its sperm) to not be eaten but to fertilize its ovules, but many pollinators just want to eat the pollen (and they have good reason for this, since a pollen grain is extremely rich in nutrients!).

A black and white microscope image of pollen grains. Some are spikey, some round, and some beanshaped with cantelope rind-looking texture.
Pollen grains have different structures and shapes. Photo: Dartmouth College Electron Microscope Facility.


As a response to this conflict, some strategies have evolved that somewhat “control” the feeding on pollen that pollinators may do. In fact, plants protect their pollen with physical structures that make it hard to be broken by pollinators. Some of these pollen grains feature spikes and thickened walls, which force pollinators to use specialized tools to break through them. Along with this physical “shield”, pollen grains often contain what are called secondary metabolites. These are chemical compounds that make the pollen indigestible or toxic, unless the organism trying to eat it has evolved ways to tolerate those compounds themselves. Closely related plants produce similar chemical compounds; the unique chemistry of a plant family dictates which pollinators can digest its pollen. This leads to different levels of floral specialization on the side of the pollinators. Pollinators will only try to visit plants that offer pollen they can digest, which again, restricts the flowers they visit. As for the previous points, increasing the different types of plants by having representatives of different plant families can increase the variety in the chemical quality of the pollen offered, attracting and supporting different types of more or less specialized pollinators.

By Anahí Espíndola, Assistant Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

The Need to Weed

Erica2 Comments

I recently got back from a 10-day trip away from home, and had to brace myself before I approached my community garden plot. I hoped there wouldn’t be pests or diseases to deal with. I was pretty sure the tomatoes would have escaped the bounds of their cages. But the one thing I knew I’d encounter was WEEDS.

A close up of various weeds in a garden setting where you can see some leaves of corn poking through.
Weeds including wood sorrel and unwanted grasses in a bed growing corn and onions.
Large okra leaves in a raised bed with various weeds underneath them.
SO MANY WEEDS in the okra bed at the Derwood Demo Garden

It was not as bad as I’d feared, but I still had to deal with a lot of unwanted plants, which is basically what weeds are. All plants have their place, but that often isn’t in our vegetable gardens, flower beds, or landscapes. I often hear from people that we should let certain weeds grow, because they are part of the ecosystem, because they support pollinators, or because they have other uses, such as being edible. In some very specific cases, these are good arguments. If I have a native plant come up in the middle of a veggie bed, I might let it grow, or more likely I would transplant it to another location in my yard (or into the row of native flowering plants I’ve established in my community garden plot). If it’s a non-native invasive that is about to produce around a thousand seeds that will spread the plant all over my yard or the community garden, I’m going to yank it, even if it has pretty flowers that the bees like. I might also let an edible weed like purslane grow, if I’m in the mood to harvest it and use it, but I’d try to contain it before it spreads too far.

Here are the main reasons that you should remove weeds from your vegetable garden, even if it’s a lot of work and you don’t feel like it:

  • Competition. In some environments, growing lots of plants close together is beneficial. Even vegetable gardens can benefit from close planting in some circumstances, to shade the soil or to confuse herbaceous insects. But weeds are weeds because they are survivors, and they tend toward domination. They will swallow up your desirable plants in no time, suck up all the water and nutrients, and provide you with nothing.
  • Reproduction. Weeds spread like crazy either via seed or by suckering roots. If you have one weed this year, next year you will have hundreds. This is bad enough in your own backyard, but if you have close neighbors, or if you’re in a community garden, you are not going to be popular. (In a community garden, you may be ousted before next year, depending on the rules and how they’re enforced.)
  • Pests and diseases. Each weed is part of a particular plant family, often the same family as some vegetable you’re trying to grow. It may harbor some of the same pests and diseases as that vegetable. Guess which plant is going to shake off the problems faster, and which one will tenderly succumb?
  • Ticks. Love to hide in weed patches and hitch a ride as you pass through on your way to the squash. There might also be other critters lurking in out-of-control weed jungles, such as snakes (good to have around, but startling), or entire rabbit families in a nest. Just to name a few. Plant a native hedgerow and let them live there, not in your tomato bed.
  • Aesthetics. I put this last for a reason, but even if you personally don’t long for a tidy garden, keep in mind that vegetable gardening as a pursuit sometimes gets bad-mouthed for being “messy” and any actually messy gardens can contribute to a stereotype. HOAs that forbid front yard veggies, neighbors that complain about completely hypothetical rats, they all learned their prejudices somewhere. Don’t let it be your garden. We all want more homegrown produce in the world, not less.

So get out there and pull the weeds! And then, think about how to stop them from growing in the first place. Here are some things you can do this summer and beyond:

  • Mulch. Put something over your soil, preferably an organic mulch like shredded leaves, straw, or dried grass clippings. You can even use weeds as mulch if they don’t have seeds on them. Compost can be a mulch if you are sure it’s been heated enough to kill weed seeds. Synthetic mulches like black plastic or weed barrier fabric are also an alternative, though they won’t add organic matter to your soil. When you disturb the soil to put in plants or seeds, try to cover it again to prevent the germination of weed seeds that have been brought to the surface. (Obviously, don’t put a thick layer of mulch over the seeds you just planted.) Mulch is also great at keeping the soil from losing moisture in the heat, and maintaining it at an even temperature. And it may help prevent fungal spores from splashing up from the soil onto your plants.
  • Learn to ID weeds. Know your enemy! As you pull a weed, use a plant ID app or other source to identify it. After some time and work, you’ll know the common ones and you can learn about how and when they reproduce. Do I have to get the whole root out (yes, for perennials) or can I just remove the top of the plant before it goes to seed (usually, for annuals)? How early in the year do I have to get out there to start pulling weeds? (Earlier than you think, alas.) The other advantage to knowing weeds is that you’re less likely to mistake them for the plants you want to grow, and vice versa. Close observation works equally well for identifying veggie seedlings. Be an informed gardener!
  • Think about growing in containers. Refreshing the potting mix every year will definitely mean fewer weeds.
  • Speaking of which… think about containing or restricting plants that are desirable but act like weeds. Various mints and their relatives, shiso/perilla, leaf fennel, some amaranths… I have personal knowledge of how badly these spread, and I’m sure every gardener has a similar list. Whether you trap the roots in a pot (on a paved surface, in the case of mints) or make very sure to cut off the tops before the seeds go flying, it’s a responsible thing to do and will spare you a big surprise come the next growing season.

And lastly, be patient. Weed seeds lurk in the soil for many years, so they probably will keep coming back. There will be setbacks. But eventually, things will get easier and more enjoyable, and (mostly) weed-free.

By Erica Smith, Montgomery County Master Gardener. Read more posts by Erica.

Small but mighty. The amazing ground-nesting bee!

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The summer is almost here, and if you are like me, you have already been outside and seen a bunch of tiny bees digging, digging, digging, and buzzing around flowers. Who are these little ladies? And what on earth (pun intended) are they doing? In today’s blog, I want to explain a bit about these super powerhouses, how they do what they do, and point to some of these cool bees that we can find right here in Maryland and our general region.

What are ground-nesting bees?

As its name indicates, ground-nesting bees are bees that nest in the ground, mostly by digging their nests. Ground-nesting bees are found in several families of bees, and being a soil nester/digger is actually one of the most common nesting strategies among solitary bees. In these bees, once the female finds a good nesting site, she starts excavating it to create an underground nest, which often has several brood cells, in which the larvae develop. These nests are usually found in spaces where the vegetation is sparse or the soil bare, and can sometimes be built along with other nests of the same species, leading to communal nesting areas. It is because of this preference for relatively open ground that it is often recommended that at least some uncovered ground is left in our green spaces, which helps provide habitat for their establishment.

A tiny bee is seen crawling out of a mound of soil on the ground.
Ground-nesting bee coming out of her nest. Photo: Colleen (CC0).

How do ground nesters build their nests?

As good miners or soil diggers, ground-nesting bees also have specific behavioral and morphological traits that make them good at what they do. Bees that excavate have modified leg structures that allow them to easily move within tunnels, strong mandibles that they use to actually dig the cavity, and modified extremities of the abdomen (the pygidial plate) that function as sorts of trowels and allow them to pack soil on the walls of the cavity they are digging.

Along with having the right tools of the trade, these bees are also selective of the type of soil they use to build their nests. Most ground-nesting bees prefer soils that are not too compacted, with at least some sand content, which makes them easier to dig through. This means that it is more likely that we will find these bees in rockier/sandier soils than in super clay-y ones. As a matter of fact, many ground-nesting bees are associated with dune nesting, and because dunes are often endangered habitats (because they are often disturbed/destroyed by human activities), many sand-nesting specialists end up becoming endangered as well. And as a fun fact about soil choice, bee experts think that because finding “good soil” is so important for the survival of these bees, bees tend to become associated with specific spots for nesting, with the nesting site becoming a sort of “family place”, where several generations of females from the same family line come back to nest over the years/generations.

A close up of the pygidial plant which is a small darker triangular structure at the tip of the bee's abdomen.
The pygidial plate is a structure present at the tip of the abdomen of ground-nesting bees that functions as a trowel. Photo: MN Native Bees.

Because digging through the soil with their mandibles (and sometimes their legs) is hard work, bees usually tend to choose the best timing to start their digging. In fact, the hardest part of the soil to dig through for a bee is the surface, which is often the most compacted. For this reason, bees tend to start digging after the soil has become moist (e.g., after rains). Incredibly, some ground-digging bees are even able to add, if needed, secretions or even nectar to humidify and loosen the soil! Once the bee has started her excavation, she continues digging deeper and bringing soil out of the construction area, which leads to all sorts of “mounts” being built around the nest entrance and sometimes chimney-looking structures.

What are some ground nesters from Maryland?

Andrena vicina – The neighborly mining bee

a close up of a bee gathering pollen from white flowers
Andrena vicina. Photo: K. P. McFarland (CC0).

This Andreniid is relatively large (about 1- 1.5 cm), present in North America and common in the Eastern USA. This species received that cute name because it is one of those that builds communal nesting areas (“neighborhoods”). In Maryland, the species is active right now (~June/July) and is generally seen visiting many native plants and crops. In particular, this is one of the known visitors of, among other plants, Rhododendron and Azaleas, several heather family plants (like Vaccinium, Kalmia), as well as several rose family plants (Prunus, Rubus).

Augochlorella aurata – Golden sweat bee

a tiny metallic green sweat beed in the center of a yellow flower

Augochlorella aurata. Photo: C. Martin (CC0).

This is a species in the Halictid family, and is called a sweat bee because it is often found collecting sweat (for water and salts). This is one of those tiny bees that you may find landing on you on a hot day, really committed to not letting go of your skin! This particular bee is relatively easy to recognize because it is small, metallic-looking, with beautiful green/golden iridescence. This bee is not fully solitary and is a species recognized to display primitive eusociality (for example, honey bees are true eusocials). In this species, there is a queen that starts a nest, and across the season, generations of first infertile and later fertile workers are produced. By the end of the season, the fertile workers are inseminated and disperse to overwinter. This bee species is pretty generalist in its choice of plants, known as a pollinator of many crops (e.g., apples, tomatoes, watermelon) as well as native plants.

By Anahí Espíndola, Associate Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

Dealing with Pest Issues in Container Vegetable Gardening

Erica3 Comments
Close up of a gey squirrel eating potted plant sitting ontop of a brick wall.
Wildlife can be cute, but also destructive! Photo via Adobe Stock

You’re happily growing lettuce in a salad table, watching the little seedlings get bigger, and then one day half of them have been dug up and tossed aside. Or you’re about to harvest your kale and then realize it’s full of holes and little green caterpillars. Or your eggplant leaves are suddenly nothing but lace. Maybe someone is stealing your tomatoes, or—more insultingly—taking a bite out of each of them. Or maybe everything is just… GONE.

Pest issues are not unique to container gardening, of course—all veggie gardeners deal with them. But just as containers have their pluses and minuses in every aspect of food growing, they sometimes provide specific challenges and benefits when it comes to dealing with pests – whether insect or animal.

By the way—let’s acknowledge here that the creatures we’re talking about are just trying to get along and feed themselves. They don’t know that they’re putting us to extra trouble (even if it really seems like squirrels in particular are just trolling us). It would be great if we could jall just get along without harming each other. So the proposed solutions below don’t go as far as hurting or killing anything (if you want to use pesticides against insects, that is up to you, though please be sure to carefully follow the label instructions). These methods all follow four principles: Location, Exclusion, Deterrence, and Distraction.

PART ONE: INSECTS

Here’s a typical scenario from Home and Garden Information Center’s Emily Clark-Waterson:

I planted kale in a flower box in the spring in a new self-watering flower box container, hanging off my balcony railing. It grew beautifully and I was able to clip young leaves and let them keep growing until the summer weather got too hot. I planted it again in late August for a fall harvest, except this time I started to notice some leaf damage and found a type of Imported Cabbageworm. These moved fast and left little to be harvested. They like to hide along the midribs. Lesson learned: Always cover your brassicas with insect netting or floating row cover to help prevent this. A small piece of tulle from a craft store works well, or you can purchase various-sized mesh bags to put over containers. I won’t be making that mistake again.

Kale leaves with large holes and small green caterpillars resting on the leaves
How many cabbageworms can you find? Photo: Emily Clark-Waterson
A small green caterpillar on the underside of a kale leaf.
They really can be camouflaged in the leaves. Photo: Emily Clark-Waterson
A larger green caterpillar rests along the midrib of a kale leaf with large holes in it.
This one has eaten well! Photo: Emily Clark-Waterson
Two containers with vegetable plants sit along a white picket fence. Each container we had a tomato cage and piece of tulle draped over it
Prepared for pests this year with tomato cages and tulle held together with clothes pins. Photo Emily Clark-Waterson

This is a great example of Exclusion. In fact, covering plants with materials like this solves the majority of insect problems—and it’s so much easier and cheaper in a container than covering a long row in an in-ground vegetable garden. Here are some other examples of plants in the brassica family being covered to protect them:

Fine mesh instect netting stretched over plsatic hoops that are over a container of greens.
Insect mesh and hoops over Asian greens. Photo: Lily Bruch
a container on the edge of a raised bed garden with a sheer cloth covering some greens growing. The cloth is draped over and tied around the conatiner with a black string.
Floating row cover over brassica plants keeps caterpillars and other pests away. Photo: Robin Ritterhoff

Plant covers work against other insects as well, for example, to keep flea beetles off of eggplants. But in this case, growing in containers provides another advantage, one of Location. Erica Smith has had success over the years by growing eggplant in containers on her deck, which keeps them well away from the flea beetles in the soil below. MG Robin Ritterhoff also uses this method, making sure to replace at least the top third of the potting soil every year in case beetles are lurking. But MG Lily Bruch says her eggplants still get eaten despite growing on a deck, so she uses row cover and also plants marigolds in hopes of Deterrence. Sometimes strong-scented plants either confuse or annoy insects and keep them away from your vegetables. It’s worth trying, since flowers also bring in much-wanted pollinators and other beneficial insects.

And what if the insect eating your plant is actually beneficial? MG Mary Anne Normile writes:

[It’s a tough call] when Eastern black swallowtail caterpillars feed on container parsley. I love the butterflies, but the caterpillars can denude a parsley plant in short order. No good solution unless you have another desirable (to the caterpillars) plant to relocate them to, except possibly to have a fresh batch of parsley seedlings on hand to plant for the short period after the caterpillars stop feeding and the end of the growing season.

If you have room, you can plant extra herbs in the parsley family, such as dill and fennel, which the swallowtail caterpillars will also enjoy. (Also make sure to have lots of nectar-producing flowers for the adult butterflies.) You could also cover up a few of the parsley plants to keep them just for you.

When pest problems arise in container plants, make sure you address them quickly, because it’s easy to lose your entire crop in very little time.

PART TWO: ANIMALS

(Yes, insects are animals; let’s not be pedantic.)

Erica here:

This is a photo of the gate to my old vegetable garden:

A half eaten tomator sits ontop of a wooden railing of a gate.

This is a typical squirrel move. Didn’t even eat the whole tomato and left it in an obvious place just to taunt me. Photo: Erica Smith

And this year, I have a squirrel who loves Swiss chard:

Squirrel seen through a window screen sitting on the edge of a planter on a deck eating lettuce.
It ate every single seedling out of the deck planter, leaving the lettuce alone, and then climbed into my garden and snacked on the beet leaves. Oh well, no Beta vulgaris for me this year! Photo: Erica Smith

Mary Anne writes:

I have had squirrels … dig up freshly planted basil in containers. They seem to love fresh soil. They don’t eat the basil, they just dig up the plants and sometimes toss them out of the container. I replant them and sprinkle the surface of the soil liberally with cayenne (the cheapest stuff, not Penzey’s), repeated after a rain, and that deters them. Once the basil plants are large enough, the squirrels don’t bother them.

Squirrels do instinctively dig in fresh soil, sometimes burying nuts, but other times looking for food or following up an interesting smell. Lily reports that they dig up her lettuce seedlings; her solution is to cover the container with a metal grid or chicken wire.

Planter box on a deck with lettuce plants growing in it. Metal chicken wire is formed over the top.
Chicken wire to exclude squirrels Photo: Lily Bruch
Salad greens grow up through wire mesh in a planter box on a deck.
Metal wire grid to exclude digging squirrels Photo: Lily Bruch
A white flower box with salad greens sits on the edge of a flagstone path. A pink netting food tents resting rests on top of the container blocking wildlife from digging.
Picnic food tents resting over a container is enough to keep the squirrels from digging up new lettuce seedlings. Photo: Emily Clark- Waterson

Lest you think this section of the blog is all about squirrels, they are, in fact, one of the worst pests for container gardeners (and veggie gardeners in general). They can climb anything, and they eat a wide variety of foods. And they are determined. They may be the hardest animal to stop once they start bothering your garden. Except possibly for raccoons—and former MG Nancy Moses had both of them!

Here’s Nancy describing the year she planted vegetables in containers on her second-story deck—in a yard surrounded by a six-foot fence but that backs up to woods.

The squirrels and raccoons climbed over our chain link fence, up the 13 steps to the deck, taking over the territory as their own.  The resulting poop was unpleasant!  The light-weight, conniving, hungry squirrels politely climbed over the netting held up with metal stakes in each tomato-growing pot; and the raccoons knocked over the pots and anything else in their way toward achieving their goal of mass destruction and hunger gratification. 

Nancy says that after that, “You could say that I quit; but I view it now as having just politely surrendered.” And honestly, how can you blame her? She tried the principles of Location—putting the pots up on a high deck—and Exclusion. Maybe the netting could have covered the plants more thoroughly, but the raccoons still would have knocked the pots over. The only real solution would have been Total Exclusion, meaning a fence that completely surrounded and covered the pots, which does not lead to enjoyment of the deck by humans.

So back to those principles. Location often works (in less extreme circumstances) by keeping plants in pots up high where some animals won’t venture. Most deer (we can never say all) won’t climb up steps and some won’t even venture close to a human home. Rabbits are short and don’t climb, so higher planters are unreachable. A balcony location keeps even groundhogs off, though probably not squirrels and certainly not birds.

Exclusion with row cover or netting can keep some less determined animals and birds away. Fences are another solution—you can fence off part of a deck or patio, or put your containers inside a fence in the yard (or use them as part of your regular veggie garden). Again, if you have serious squirrel, raccoon, or bird issues, only a garden enclosure with a roof will help.

Deterrence can mean using strong-scented plants to warn away animals that don’t enjoy those smells. It’s no guarantee, but maybe will stop the casual visitor.

Colorful wooden planters stacked agains an outside side to a building with herbs, annuals, and strawberries.
Colorful planters hold strawberry plants up high, and a “citronella plant” scented geranium as one of the strongly-scented deterrent plants to offend visiting herbivores. Photo: Erica Smith

In extreme cases, you can revert to growing only these sorts of plants. Herbs like rosemary and thyme, onions and their relatives, and hot peppers may be unattractive to animals.

There are other methods of deterrence if you want to try automatic water sprayers, constant noise, or bird scarers of various types. Avoid sprays that are meant to repel deer if they contain any ingredients you wouldn’t want to consume.

Distraction means giving our animal friends something else to think about. Some garden writers advise providing an alternate source of food, such as edible plants closer to the animal’s habitat, but be wary of bringing in an entire extended family that will reach your closer-to-home plants eventually. Also, be sure to keep compost containers secure if they hold food scraps, and keep fallen produce cleaned up. (We have not talked about rats so far in this post, and let’s not start now.) But do make sure animals and birds have a water source they can visit—sometimes they are eating your vegetables because they’re thirsty.

If possible, try to provide natural sources of food by planting shrubs and trees (preferably native to your region) that grow seeds, nuts and fruits. If you don’t have room yourself, use our resources to learn about native plants and try to convince neighbors or anyone else who controls plantings in your neighborhood to grow them.

Dealing with pests can be challenging, but it feels great when you rise to the challenge! Growing in containers can sometimes help you combat pests, such as when you can easily cover a pot or place it somewhere the pests can’t get to. And if you need to take a season off to regroup, it’s so much simpler to just empty the pots and put them away, rather than having to close down a big garden. Do some research, find some solutions, and come back refreshed to try again!

Share your struggles and triumphs in the comments—and best wishes!!

By Erica Smith, Montgomery County Master Gardener. Read more posts by Erica.

Enhance Biodiversity in Your Vegetable Garden by Planting More Flowers!

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A view of a fenced in vegetable garden with Salad tables in the forground and multiple raised garden beds full of various vegetables. Bright orange marigold flowers line the edges of the raised beds and there are wood chip paths inbetween the planting areas.
Marigolds line the edges of raised garden beds, bursting with vegetables in this county extension demonstration garden. Photo: Jon Traunfeld

A practice generally used in agricultural contexts is that of floral supplementation. In today’s blog, I would like to dig a bit into this idea and present some strategies to implement it at smaller scales, like small vegetable gardens and green spaces. Read along to learn a bit more!

What is floral supplementation?

Agriculture using western methods generally leads to losses of plant biodiversity in and around fields, mostly because it transforms diverse spaces into large monocultures (the crop fields). This, in turn, reduces the ability of the ecosystem to regulate pests, maintain pollination and eventually can negatively affect yield and production, along with increasing environmental erosion. As a response to these needs, strategies have been developed to increase biodiversity in agricultural contexts, and one of those is floral supplementation. In this strategy, the areas surrounding the crop fields are planted with diverse floral mixes or hedges, or the crop rows are intercropped with flowering plants. Such approaches improve soil quality and reduce erosion, increase diversity of plants and animals associated with them, and in many cases lead to improved pest control and pollination of the crop. Although this is a practice more or less widespread and recognized for production fields, it is not often officially promoted in smaller areas such as gardens or the green spaces that surround them. Let’s fix that! 😊

Why does floral supplementation work?

The idea behind these practices is that they increase the spatial and plant resources available to the local biotic community. By increasing the number of plant species present in an area, the different types of food and nesting resources are also increased and become more complex. For example, there may be flowers that bloom at different times of the season, that produce different types of nectar and can support different pollinators, fruits that support different insects and birds, plants of different heights and structure that can offer shelter to different organisms. These modifications eventually lead to more diverse animal communities being present in the area where the supplements are added. From the point of view of the benefits of these changes on the actual performance of the crop field, this diversity promotes the presence of biological control of pest agents (e.g., predators of pests, parasitoids), as well as increases the diversity and abundance of potential pollinating species. The presence of a more robust plant community can also promote soil retention through the presence of more roots to physically retain it, reducing erosion and water runoff.

Tomato plants with green tomatoes growing in a raised garden bed with a railing in the background. Interspersed plantings include basil, and chard.
A way to implement floral supplementation in small spaces is through the combination of different crops on the same pace, such as offered by the idea of companion plantings. Photo: Steph L.

Floral supplementation in gardens

Although the extent of floral supplementation done at the agricultural scale can not be reproduced at the garden level, the same principles can be implemented, especially if the gardening space is not necessarily embedded in a very biodiverse context. Here are some ideas on how to do it.

Intercropping and Companion Planting

A cool way to both increase diversity and production per unit of area is the use of intercropping with companion plantings. Here, different crops can be interplanted, with rows alternating species, or with several crop species planted in a mixed way in the same part of the garden. This relates to the idea of companion planting, where species that are planted together are selected for their ability to successfully coexist and support each other. The table gives some ideas on potential combinations to promote and avoid.

A table with a list of Crops on the left column, companion plants in the middle column, and incompatable plants in the right column. The link to Virginia Tech Extension will lead to a PDF.

Companion planting promotes the interplanting of different crops/herbs, with species known to be compatible and incompatible in these plantings. Table from Virginia Cooperative Extension publication, Companion Planting in Gardening

Hedgerows

Green bushes with pink flowers along a grassy area under trees.
Especially if planted with native species, hedgerows can offer a complex structure for a lot of animal diversity to establish close to our gardens. Photo: M. Gimber.

This strategy can be especially effective if there is a lot of room around the garden plot. Instead of leaving that as a mowed space, it is possible to turn it into a structurally and species-diverse space! For this, one can consider planting sets of native shrubs/small trees that can provide complex shelter spaces and flower/fruit/seed resources for many animals (including humans! 😛 ). Some choices I really like for our area are fringe trees, spicebushes, witch hazels, hazels, pawpaws, serviceberries, native elderberries, or redbuds. Of course, not all these species are appropriate for all areas, so depending on the level of light and soil conditions, some may be preferred over others.

Flower Strips

A close up of Monarda or beebalm with red blooms
Even when not much space is available, the planting of native herbaceous plants can lead to an important bump in diversity around our vegetable gardens. This strip of Monarda, Solidago, Penstemon, Rudbecia and some other native plants is directly adjacent to my vegetable garden and attracts many pollinators and predators such as wasps and mantids. Photo: A. Espindola.

Flower strips are also a great choice, and if space is available, one can easily turn them into a small floral meadow. These spaces can be planted with seed mixes, which can be purchased from seed companies specialized in the establishment of native meadows. (Be sure to review the species list since some meadow mixes can contain invasive or borderline invasive plants, others may contain annuals like Cosmos.) If the space available is not very large, it may be more practical to just plant a set of native flowers that bloom at different times through the season. Check out this other post where I direct people to some specific plant lists that can be handy for our area. Especially if the species chosen are perennial, the planting will lead to a long term establishment, and if wanted, new plants can be added over the years, as some species become more established.

By Anahí Espíndola, Associate Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

A Personal Experience: Learning Some Tricks for Container Gardening on the Eastern Shore

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Wooden planter box with a decorative chalkboard sign reading 'FRESH PRODUCE FROM LOCAL FARM' outdoors on a patio with grass and trees in the background.
Elevated container gardens provide convenient access to fresh, home-grown herbs and greens. Photo: Joan LaHayne

My transition from traditional, large, in-ground, tilled vegetable gardening to container gardening happened out of necessity. In 2015, my husband and I moved from Western Howard County, where we had lived on a large lot with full sun, to the Eastern Shore, with just under an acre and lots of shade/part shade throughout the yard. Most of our full sun and open space was in the front and side yard, both visible from the road. Additionally, we needed to install a sand mound septic system in the limited space we had. This would add further restrictions on what and how we could plant because deep-rooted plantings/tilling are restricted.  We decided that raised beds would be a solution because they would be aesthetically more attractive and could also provide protection from roots interfering with the septic system. 

Installing Raised Beds

Raised beds can be custom-built or purchased as a kit to assemble. We chose to build our own. We started with 4 plots measuring 8’x 5.5’ feet and approximately 1’ deep. The first beds were built using pressure-treated wood. The building material you decide on is a personal choice; they all have their pros and cons. New pressure-treated wood no longer contains arsenic, but we chose to change building materials when adding additional plots. A neighbor had Trex boards from a deck remodel, and we were able to recycle those for the additional plots. We filled the boxes with a mixture of compost (home-grown), leaf pro, horse manure (we live near Assateague), and existing soil. Although our first harvest was slightly disappointing, each year the soil quality improved, as did our vegetable yields. Each year, we typically add compost and manure, but a recent soil test revealed that this practice is creating an imbalance in the soil (too much phosphorus). Annual soil testing of each bed is a beneficial practice for us, and will hopefully improve the quality and quantity of our harvest. Typically, yearly testing isn’t necessary, though.

Adding Containers

After the first year, I realized I wanted more space for herbs and edible flowers, preferably planted closer to the house. We designed 2-foot-high long containers that would surround the existing concrete patio, closing it in. A gate and fire pit completed the design, resulting in the additional benefit of keeping young children and dogs safely away from the water. Because the boxes were so much higher, a barrier was needed to separate the top (1 foot of soil) from the bottom (empty). Our first mistake was not laying landscape fabric on the shelf to prevent the soil from running through the boards when watered. Once we corrected that, the soil remained in place, and the boxes retained water more efficiently. These boxes are beautiful and easily accessible. Because they are so close to the house, they are somewhat protected from winter winds and frost, often allowing greens such as kale, chard, parsley and collards to winter over. Additionally, the height of these gardens prevents animal “snacking” and makes planting and weeding more comfortable. 

A red concrete block patio showing container beds and a covered firepit around the edge. A lawn and wooded area in the background.
Adding the gate and firepit completed our patio space to be a functional area to relax and harvest fresh produce! Photo: Joan LaHayne
Wooden raised container beds lining a patio area in an L shape. a metal spiral staircase is also shown leading down to the patio.
Fresh spring greens emerging in the raised containers are a welcome sight. Photo: Joan LaHayne

Watering

All of the beds require more water than traditional in-ground gardens. We have still not figured out an easy soaker system, but my husband loves to water, so we monitor the beds closely and water as needed. Our goal this summer is to install soaker hoses on the first two beds, utilizing water from a rain barrel nearby. We have added a few more raised beds along the property line where we have access to maximum sunlight but are far from a water source. One contains asparagus plants that require little water (because harvested early in the spring) and the others are used for root vegetables. Eventually, we will try to find a better way of getting water to those gardens as well. 

Limited Space Solutions

The most consistent challenge of container gardening for me has been limited space. Working as a volunteer in a local community garden has allowed me to learn tricks on how to maximize yields by observing the gardening practices of others. I noticed many different ways my fellow gardeners added structures to allow vines to climb. I loved the idea of an arch that would provide a shady pathway through the garden. My husband constructed a 10’ archway using heavy reinforcement wire that was secured to the outer boards of 2 parallel beds. The resulting design was successful! Last year’s cucumber, butternut squash and spaghetti squash plants found their way up and over the arch, producing fruit that dangled from above. Harvesting was made easy and the display was beautiful. 

Large wooden raised beds in a lawn with a metal fencing arch connecting them. THere is a shed in the background and some crops growing in the beds.
Adding the metal fencing arch between the beds helped with the limited space in the raised beds. Photo: Joan LaHayne

Container gardens are beneficial in many ways. They can be placed in a variety of spaces throughout the yard and can be dismantled and moved if growing conditions change (increasing shade, for example). Because of the limited square footage in each, weeds are much easier to control. No tilling necessary. If animals are taking too much of your harvest, raised gardens can easily be fenced or built higher to keep plants out of reach. Container gardens can be incorporated into already existing or planned flower beds, creating interest and beauty, as well as expanding pollinator habitat. Although I continue to learn gardening tricks and practices, I have found container gardening to be an ideal solution to growing vegetables year-round here on the eastern shore.  

By: Joan LaHayne, Master Gardener in Worcester County, Maryland.