Monarchs and Milkweed – The Garden Thyme Podcast

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In this month’s episode, we are chatting about the marvelous relationship between monarch butterflies and milkweed.   Undoubtedly, there is no other butterfly so easily recognized with its orange and black wings fringed with white spots. Their seasonal flight from Mexico through the United States towards Canada is long anticipated for gardeners.

Timing :
Milkweed and Monarchs: ~1:36
Migration and Life cycle: ~6:58
Milkweed recommendations for Maryland: ~ 11:06
Native Plant of the Month: Joe-pye weed- Eupatorium spp. at  ~ 27:40 
Bug of the Month: Asian Tiger Mosquito at ~  ~33:05
Garden Tips of the Month at ~ 39:20

We hope you enjoyed this month’s episode and will tune in next month for more garden tips.
If you have any garden-related questions please email us at  UMEGardenPodcast@gmail.com  or look us up on Facebook at https://www.facebook.com/GardenThymePodcast

The Garden Thyme Podcast is a monthly podcast brought to you by the University of Maryland Extension.  Hosts are Mikaela Boley- Senior Agent Associate (Talbot County) for Horticulture, Rachel Rhodes- Agent Associate for Horticulture (Queen Anne’s County), and Emily Zobel-Senior Agent Associate for Agriculture (Dorchester County). 

Theme Song:  By Jason Inc

How plants cope with soaring temperatures

Hot enough for ya?  It’s only July, but we’ve had more than our share of relentless heat.

Have you ever wondered how plants cope with heat?  It’s not as if they can turn on their air conditioners or pour themselves a cold one.  In fact, plants have myriad adaptations that help them survive high temperatures.  Some involve managing heat while others focus on conserving water.

  • Many coping mechanisms are structural.  Plants such as sedum have waxy leaves to conserve water.  Fuzzy lamb’s ear has reflective leaf hairs. 
  • Ornamental grasses’ rolled leaves give them an advantage as does threadleaf coreopsis’ smaller, finer leaves.  Less surface area means leaves lose less water.  
  • Lavender, Russian sage and other plants with bluish leaves are summer survivors, too.   
  • Plants with thick roots such as iris, peonies and daylilies store water better. And native plants’ deeper roots find water more easily.   

All of these evolutionary adaptations help plants tolerate hot, dry conditions. We know that summer’s heat comes every year and that global warming is bringing more temperature extremes.  So it makes sense to help our gardens adapt by incorporating plants with these characteristics.  

Okay, science geeks.  Here’s one for you.  Did you know that some plants can make special “heat-shock proteins” to help them recover from heat stress?  When you cook an egg, you are unfolding proteins.  When you melt butter, you are disrupting cell membranes.  These same disruptions can happen when plants get too hot. Cell membranes can literally melt, leaking plant’s vital fluids. Heat-shock proteins act like “molecular chaperones,” preventing these bad things from happening at a cellular level.  They beef up membranes and collapsing proteins.  Plants survive.

But don’t make plants go it alone, relying only on their adaptations.  Help them when it’s hot by watering them more often and deeply. Newer plantings of trees and shrubs need slow, deep soaks once a week.  Use a hose on a trickle, a soaker hose, drip irrigation or a 5-gallon bucket with nail holes in the base.  

Container plants heat up and dry out faster, so check and water them once or twice a day. Soak them until water runs out the drainage holes.

Keep plants mulched to conserve moisture.  Consider shade covers on vegetable crops.  And be vigilant, watching your plants for signs of heat stress such as wilting.

Water moves constantly from the soil to roots, stems and leaves.  There it escapes through leaf pores.  When the rate of water lost is greater than the water absorbed, plants wilt and need water. 

Trees often jettison some leaves to conserve water when it’s hot. Fewer leaves need less water. Unless leaf loss is dramatic, there is no cause for concern.

Vegetable plants slow production in high heat. Blossoms drop when temps top 80 degrees. Without blossoms, plants can’t make fruit. 

Tomatoes, squash, peppers, melons, cucumbers and beans are likely to drop blossoms. It’s a passing phase. Plants will make flowers and fruit again when temperatures cool.

Green peppers
Summer’s high temperatures cause blossoms on some vegetables such as these peppers to drop, temporarily slowing production. Photo credit – Home & Garden Information Center

Plants have developed miraculous adaptations to high temperatures, but sometimes need our help. So watch, water and marvel at the many ways nature finds ways to beat the heat.  

Annette Cormany, horticulture educator, University of Maryland Extension – Washington County

Pitcher plants: their pools are cool, but not always refreshing

As I’m writing this, my weather station tells me that it feels like 95F outside, and now all I can do is think of jumping into a pool. And because in the natural world pools are not just for refreshing and drinking water, today I wanted to talk about a special natural wonder of our region, a plant that makes pools to have things jump in them… although it doesn’t always end up as a refreshment. Let’s talk about our local pitcher plants!

Pitcher plants are native to many regions of the USA, and one of these plants, the Northern or Purple Pitcher Plant (Sarracenia purpurea), is native to right here! Pitcher plants receive their name from the fascinating structure they have, which allows them to collect fluids, create a sort of pool, and use it to trap prey (usually small arthropods) that they feed upon. Although we tend to think of carnivorous plants as feeding on insects, pitcher plants have a really interesting relationship with them, since they both feed on them, while also needing them to reproduce through pollination. How does this work?

native pitcher plants in a field
The Northern or Purple Pitcher Plant is native to Maryland. Photo: A. Carlson.

Are pitcher plants really carnivorous?

First things first; let’s talk about plant carnivory. Carnivorous plants are an organism that reminds us that nature is always ready to fascinate us in the most unexpected ways. Plants usually grow by absorbing minerals from the soil and combining them with the sugars they synthesize by using the energy from sunlight and CO2. In some nutrient-poor habitats, however, conditions may be a bit too harsh to obtain sufficient minerals and food to survive. In those habitats, other feeding adaptations to supplement these low nutrient levels have evolved, allowing plants to obtain sufficient food to properly develop. The evolution of carnivory in plants is one of these strategies.

Although pitcher plants are carnivorous, this does not mean that they are a sort of plant-lion waiting there to attack and retain prey. Their ways are more intricate, and in some ways, more fascinating than those of an animal predator. As all plants, pitcher plants are not able to ingest their prey; they have no mouths, no teeth… so how do they do it?

pitcher plant
Pitchers in pitcher plants fill with rainfall and get slowly colonized by a multitude of microbes and other organisms. Photo: A. Carlson.

In pitcher plants, the pitcher (a special modified leaf) fills with a liquid formed by water (often from rainfall) and other compounds that make it really favorable for the establishment of microbial communities. Along with the secretion of some plant digestive compounds into the fluid, it is these microbes that actually digest the insects that fall into the pitcher. Once the prey is trapped in the pitcher and then digested, the plant is able to absorb the released nutrients directly through its tissues, eventually obtaining food from animal tissues, thus becoming a carnivore.

Why do insects fall into the pitcher?

Insects are often attracted to the pitcher by the many lures that the structure has. For instance, the walls of the pitcher display lines and markings that are attractive to insects, which direct them to the lid of the pitcher. At the edges of those lids there are small glands that secrete nectar, which is also mixed with some narcotic substances that make insects lose control of their bodies. Once these insects experience the effects of these substances, they lose grip and fall in the pitcher, where hairs and a slippery and narrow surface prevent them from crawling or flying out.

insects inside a pitcher plant
Many small insects fall into the pitchers, where they are digested by the pitcher microbial communities. Photo: A. Carlson.

But pitcher plants need to be pollinated too! How do they do it, if they eat insects?

Yes, pitcher plants need the service of pollinators to produce seeds and reproduce. And indeed, they also have very pretty flowers (which in Maryland bloom in May-June). So, how do they attract pollinators to their flowers instead of to the pitchers, and then, not have them fall in the pitchers by mistake? 

Studies on this are demonstrating that pitchers and flowers in pitcher plants are not active at the same time. While the plant flowers only for a very restricted time in the year, the pitchers are active most of the growing season. However, their level of activity and attraction are reduced during the flowering time. This means that pitcher plants have evolved to allow pollen transfer to happen without endangering the valuable pollinators.

pitcher plant flowers
The pitcher plant flowers are very pretty, with a special round shape and coloring. In Maryland, pitcher plants bloom in the months of May and June. Photo: B. Wheeler.

Pitcher plants are tiny ecosystems

With more and more studies done on these plants, it is now clear that the fluids in the pitchers behave really like tiny ecosystems. In some cases there are not only microbes that help the plant get their nutrients, but also other organisms that feed on these microbes. There are organisms that use the pitcher’s fluids to develop (the larvae of some mosquito species are specialized in developing in these fluids). The pitchers also are used by other arthropods to trap prey (some spiders build their webs in the pitchers).

mosquito larvae in pitcher plants
Some mosquito species, like this Maryland specimen of genus Wyeomyia, have evolved to be able to develop exclusively in the pitcher fluids of pitcher plants. Photo: K. Schultz.

I love pitcher plants and I want one in my house

It is absolutely great to be interested in carnivorous plants and pitcher plants in particular. Unfortunately, the Northern Pitcher Plant is currently classified as Imperiled in our State. Indeed, many of the habitats they prefer (bogs, peatlands) are endangered, or have been profoundly disturbed by human activity. Another additional pressure that our native pitcher plants experience is collections from the wild for trading. Indeed, the market for carnivorous plant lovers is huge, and it is cheaper for a seller to collect a plant from the wild than to grow it from seed in a nursery. If you are considering purchasing pitcher plants for growth at home, make sure that the plant you buy has not been collected from the wild.

By Anahí Espíndola, Assistant 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!

Wild ginger spices up the Maryland spring

As a pollination biologist, I have the immense privilege of studying really cool plants who trick their pollinators in fancy and incredible ways, and I tend to be naturally attracted to flowers that may not be super showy to most (but are among some of the most mind-blowing things in nature). These flowers are such a wonderful thing in their own right, and in this post I want to do them justice. Because it’s spring and some of these are starting to point their noses out of the ground, in today’s post I would like to (re)introduce you to a plant you may be familiar with, but that I hope after today you will get to look at with new amazed eyes (in case you don’t already 😉 ). Come with me and let’s chat a bit about the wonderful hidden queen of our forests: the wild ginger!

Is wild ginger, ginger?

The short answer is no. While ginger (the plant we eat) is native to Southeast Asia, wild ginger (Asarum canadense) is native to right here, and more specifically to the deciduous forests of Eastern North America. In case you are not familiar with the plant, it belongs to the family of birthworts, which have really interesting ways of interacting with their pollinators. Unlike other birthworts that tend to have flowers that hang in the air from the plant, wild gingers are very “shy” and the whole plant is restricted to the ground level.

Wild ginger is starting to peek out their leaves right now. Once the leaves are fully grown, they get their characteristic heart-shape and can create nice mats to cover the ground. Photos: A. Espíndola; threelark.

The plant is perennial (it lives for several seasons) and exits dormancy in the early spring when its heart-shaped and fuzzy leaves start to unfurl and emerge from the ground. Eventually, the plant becomes a little mat and over time it creates colonies. This is a reason why wild ginger can be a great groundcover plant to use under trees or in shadier and humid parts of one’s yard (see here for how to do this).

Wild ginger is cool – The flowers!

Unlike other birthworts, wild ginger holds its flowers close and parallel to the ground. Wild ginger’s flowers are not showy, being of dark brown and not very large. These flowers are engaged in mimicry pollination, meaning that “disguise” as something else (here, fungi), to trick pollinators into doing something they don’t necessarily want to do. In the case of wild ginger, the flowers are held low to the ground and close to the base of the stems.

Wild ginger flowers are displayed on the ground, at the base of the fuzzy stems. Being dark and close to the ground helps them lure their pollinators, small flies that feed on decaying matter. Photo: A. Carlson.

Wild ginger flowers are dark, particularly moist, and produce specific odors that attract small flies that feed on decaying matter. The tricking consists in making the flies enter the flowers to lay eggs in what the flies consider is fungi (their egg laying sites). While doing this, the flies contact the pollen-bearing structures, and while visiting different flowers, they cross-pollinate them. In this case, we talk about antagonistic interactions between the plants and their pollinators because the interaction does not benefit both partners. In fact, here the plants have the upper hand, and the flies simply loose their eggs to the plant since their larvae can’t feed on the floral tissues. If this is not sufficient to amaze you, keep reading; it gets better!

Wild ginger is cool – The seeds!

After pollination, the flower ovules grow into seeds. Unlike seeds in most plants, wild ginger seeds have a special “addition”. Indeed, the seeds have attached a special extension (called an elaiosome) that is particularly rich in lipids and proteins. This structure makes the seeds very attractive to ants, who collect the seeds, carry them away from the plant, and, after having consumed the elaiosome, discard the seed. By doing this, the seeds can get dispersed farther away from the mother plant, and the population can slowly grow and expand. Isn’t that super neat????!!!

The seeds of wild ginger have a special nutrient-rich body called elaiosome, which is a delicatessen for ants. This allows the plant to use ants to disperse their seeds. The shiny brown (left) and yellow (right) bodies attached to the seeds are the elaiosomes (arrows). Photos: Sid Vogelpohl, Arkansas Native Plants Society; B. Patterson.

Wild ginger as a human ally

Wild ginger was and is still well known to Native Americans of Eastern North America, and it is very likely that they were the ones who showed the European colonists how to use it. Among the Native names still known for this plant is namepin (see here to learn how to say it), which means “plant of small tubers”. Even though it is hard to find the original local names for Maryland tribes, we know that the roots of the plant were used to treat fever and coughs by Cherokees, Iroquois, and Rappahannocks, and that it is very likely that most of the tribes and bands of Maryland (e.g. Shawnee, Piscataway, Pocomoke, Assateague, Nause-Waiwash, Accohannock) use(d) it as well because the plant was and is abundantly present in the area.

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

New! 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!

Hummingbirds Add Grace to the Garden

In a few weeks, they will return; flashes of emerald green winging their way through our gardens. The hummingbirds will be back.

Around April 15, hummingbirds return from their winter digs.  Weighing about the same as a dime, they pack plenty of power in that petite package.   Their wings beat 50 times a second and their aerial acrobatics are second to none. 

Our local hummingbird is the ruby-throated hummingbird.  The males sport a jaunty red handkerchief of feathers they flash to attract females and warn off aggressors.  Hey, baby.  Whoa, bud. 

As they dip their bills into flowers, hummingbirds pick up pollen on their feathers which they transfer to other flowers.  Bees and butterflies get all the press, but hummingbirds also are good pollinators.

Hummingbirds’ powerhouse metabolism needs constant fuel.  One hummingbird needs the nectar from about 1,000 blossoms a day to survive.  As gardeners, there is much we can do to help these flying jewels.

To attract hummingbirds to your garden, plan blooms from April to October to provide them with a steady source of nectar.  They supplement their diet with tiny insects and spiders, but it’s nectar they need most.

A perfect addition to your garden is the native columbine, Aquilegia canadensis.  It blooms in concert with the hummingbirds’ arrival in April when few flowers are blooming. Plus, it has the tubular form that’s custom-made for a hummingbird’s long, slender beak.

The rumors are true:  hummingbirds favor red and orange flowers.  If they also have a tubular shape, your hummingbirds will be ecstatic.  Think coral honeysuckle, salvia, and bee balm. 

Some plants fool you by having a hidden tubular base.  Look at a petunia, morning glory, lantana, or phlox to see what I mean. 

Nectar-heavy flowers without tubular shapes score big with hummingbirds, too.  Lupines, hollyhocks, and foxglove are all favorites.

Plants provide wonderful natural food sources for hummingbirds, but many people – myself included – like to put up hummingbird feeders.  The best feeders are sturdy, easy to clean and hang, and have multiple ports and perches. 

Skip the pre-made hummingbird food mixes and make your own.  Simply dissolve 1 part sugar in 4 parts water.  I boil a cup of water and add a quarter cup of sugar.  Clean and refill your feeders weekly. 

Hummingbirds prefer showers to baths, so you can make them oh-so-happy by adding a water dripper or mister to your garden.  They will delight you by dancing in the spray.

If you’d like to help your hummingbirds even more, avoid using chemicals in your garden.  Their fast metabolism and tiny size make them especially vulnerable to insecticides and herbicides.  So, use kinder, gentler controls.

I hope you will welcome hummingbirds into your garden this year.  There are few sights more joyful, few birds more charming.   

Some plants are not cool, skunk cabbage heats up

IMG_3725-eastern skunk cabbage at pine hole bogEastern skunk cabbage at pine hole bog by dreamexplorer is licensed under CC BY-NC-SA 2.0

The middle of the winter may seem like an odd moment to think about flowers. In fact, if I look out my window, I can barely see the ground, with most of it covered in snow or ice. So, flowers and all the greenery of spring and summer seem like something that happened in another world which today seems sooooo far away! There are some flowers, however, that defy some of these rules of low temperatures and do a revolution in nature (OK, maybe not a revolution, but still…). In today’s post, and although surrounded by ice and snow, I invite you to join me and warm up using the heat that some plants produce, since we’ll be talking about heat-producing plants!

Really?! Can plants produce heat?

The short answer is yes, which is super cool in itself. The long answer is yes, but let me tell you how, and what are the advantages of producing heat (and why not all plants do it).

The production of heat in plants is relatively rare, and this feature is found mostly in plants considered to have evolved a long time ago from an ancestor to most living plants. Today, heat production in plants is restricted to groups associated mostly with tropical and subtropical environments, such as water lilies, aroids, palms, and birthworts.

Unlike what we may expect, heat production in these groups has not evolved to keep the plant alive, but rather to help the plant reproduce. In these groups, heat production is associated with floral maturation and in particular to pollinator attraction. In these cases, different parts of the flowers increase their metabolism at a specific point in their development, leading to an increase of temperature that in some cases can be extremely noticeable.

In some cases, the heat has been described as a reward for pollination. (Check out this other post for other “special” rewards pollinators get from plants.) This is because it may occur at times of the year (or the day) when the environmental temperatures drop a lot, and when pollinators that visit the flower could benefit from an extra source of heat.

In other cases, heat is known to promote the release and spread of floral odors, which attracts the preferred pollinators. In many cases where heat production is present, it has been observed that plants also display a way to retain the pollinators, such as floral chambers, and in many of those cases the interaction between the plant and its pollinators involves luring and temporarily trapping the pollinators!

plants in the arum family
Some arum family plants (here, the European Arum maculatum) temporarily trap their pollinators. The species shown here displays a chamber in the lower part of its “flower” that is closed by hairs (shown on the right), which let the insects in but makes it hard for them to leave. While the flies are trapped in the chamber, the flowers mature, dropping pollen on the flies. These flies will be released after a while, and some of them will be caught again by another plant, leading to the cross-pollination of the species. Sneaky, sneaky! Photos: A. Espíndola.

While it takes a lot of energy from the plants to produce heat, this usually allows them to flower early in the season while other flowers are not around. This reduces inter-plant competition for pollinators, makes the plants easy to find by pollinators, and increases the chances of having pollen be transferred from one flower to another — all of which increases the number of seeds plants are able to produce.

Our very own heat-producing plant, the Eastern skunk cabbage

Many of you may be familiar with Eastern skunk cabbage (Symplocarpus foetidus), which is among the first plants we see peek out their leaves in the snow or the ice in the early spring. Besides being among the first plants to appear in our region, they are actually also among the first to flower, and that flowering and their pollination are intrinsically related to heat production.

Skunk cabbages belong to a mostly tropical family of plants, the arum family (Araceae). Fortunately to us, some of them do occur also in more temperate regions like ours (another native Araceae from our region is the beautiful Jack-in-the-Pulpit, Arisaema triphyllum). As with many other Araceae (for example, the titan arum), skunk cabbage attracts their pollinators through the production of a very pungent odor, which gives the plant its common name. And like all Araceae, their flowers have a very special shape that allows them to not only produce but also retain heat.

skunk cabbage
The skunk cabbage has a typical arum family flower with a bract that covers the central part of the flower. The central part displays all the reproductive parts. In the picture shown here, it is possible to see the yellow pollen exposed on the flowers of this plant. During flower maturation, the reproductive part heats up, reaching temperatures of over 20˚C (about 70 ˚F)! Center and right images show pictures of the flowers taken using a camera able to measure surface temperature, with a color scale that relates shown colors with temperatures. Photos: left: Janet and Phil; center and right: Onda et al. 2008.

When their flowers start to mature, the “head” of the flowers heats up reaching temperatures of about 70˚F (!!!), even if the surrounding temperatures are below freezing. This heating leads to the release of aromatic odor bouquets, formed mostly by compounds rich in sulfides (thus, the stinky odor). Even though this odor may not be the most attractive to us, it is very much so to the skunk cabbage’s favorite pollinators: small flies and beetles that may be lured by the flower “thinking” it is their favorite food or egg-laying site.

In defense of the plant, though, even though the attraction may be slightly dishonest, the lured pollinators may actually benefit a bit from the visit. While some of them may indeed find laying sites on the plant material, most of them will benefit from the heat received, which especially that early in the season is a much welcome reward! This heat also allows the pollinators to become more active and sometimes even mate within the plant’s flower, which also benefits their own reproduction. Finally, and most importantly for the plant, through this heat release and all the insect movement associated with it, insects passively pollinate the flowers, getting covered in pollen and later transferring it to other equally stinky and warm skunk cabbage flowers. Isn’t this super cool?… I mean, warm?

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

New! Anahí is starting 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!

Readers’ 2020 Gardening Highlights Vol. 2

At the end of 2020, we asked readers to share any notable stories, projects, or accomplishments from their past year in gardening activities. We received some great submissions. We will feature a portion of the submissions in this post and more in the future.

View more 2020 Highlights

Pollinators love Mexican sunflower

Anne Henochowicz in Montgomery County wanted to share her success with this pollinator attracting plant.

Pumped about pumpkins

Kelly Domesle and daughter Helena had great success with pumpkins down in Washington D.C.

“During the shutdown this Spring, we spent an afternoon exploring the physics of “Pumpkin smashing” from our deck. My daughter, Helena, salvaged a few pumpkin seeds and planted them in our front yard. I was skeptical, but she tended to the plants all summer and had an amazing harvest this Fall! People stopped and talked to us about our pumpkin patch all year and we loved watching the bees buzzing in and out of the flowers. We gave the pumpkins away to neighbors and cooked some, too.”

  • Pumpkin harvest
  • Big pumpkin patch
  • Pumpkin vine

Brittany’s bountiful Baltimore garden

Brittany Croteau, a Master Gardener in Baltimore City shared her amazing turf reduction/garden expansion, native flowers, and fruit and vegetable haul this year:

“Over 2020 I anticipated having a really sad garden year… I was newly pregnant, and had just accepted a promotion which had me traveling to Cecil County daily, which left me with little time to think about my garden. Then COVID hit and I found myself at home 24/7, with a LOT of free time on my hands. My husband and I decided to rededicate that time to our garden, removing more turf, planting more natives, and meeting (socially distanced) with neighbors to swap produce and flowers. This year was the most fruitful garden we had, both with native plants, native birds, and veggie production. I was so grateful to spend time outside and create a space I was happy to welcome my daughter into in August 2020. A year I thought my garden was going to be neglected ended up being our best garden year yet. “