Maryland Grows

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.

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:

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:

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

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.

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.

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.