Goldenrods: The Garden Thyme Podcast

goldenrods episode of The Garden Thyme Podcast

Gold and yellow hues are the undeniable colors of autumn. In this episode of The Garden Thyme Podcast, we discuss one of our favorite yellow-blooming perennial plants – goldenrod. With its pretty yellow flowers, long blooming seasons, and high wildlife value, what is not to love about these fantastic native plants? Mikaela also counts down her top pick of goldenrods for different gardens (~17:10). Her goldenrod bloom chart can be found here.

We also have our: 

  • Native Plant of the Month – Pawpaw (Asimina triloba) (~22:45)
  • Bug of the Month – Goldenrod Bunch Gall Midge  (~33:35)
  • Garden Tips of the Month (~39:15)

If you have any garden-related questions, please email us at or look us up on Facebook.

For more information about the University of Maryland Extension (UME) and these topics, please check out the UME Home and Garden Information Center.

The Garden Thyme Podcast is 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 

Cicada Killer Wasps Are Scary But Good

a close-up view of a cicada killer wasp showing its light yellow and black striped abdomen
Cicada killer wasps are good pollinators who keep cicadas in check.
Photo: Dawn Dailey O’Brien, Cornell University

It’s big. It’s creepy. It’s the cicada killer wasp and it has some local folks worried. But it’s a good guy. Honest. 

Looking like yellowjackets on steroids, 2-inch-long cicada killer wasps are yellow and black and a bit intimidating. But it’s all a show. 

Unless you’re a cicada, you have no worries. These wasps help control the annual cicadas buzzing in our trees.

In fact, male cicada killer wasps don’t have stingers at all and females aren’t likely to sting unless you step or sit on one.

In addition to their ginormous size, cicada killer wasps worry folks because they do figure eights over lawns, looking like they are Up To No Good.

Nope. Those are just males establishing or defending territory. Boys will be boys. 

The dudes have been hanging out since July, scoping out territory while waiting for the ladies to arrive. Their manly posturing results in often spectacular wing-whirling combat, all bluster and bluff.  

Check out the video of a close encounter with University of Maryland entomologist Mike Raupp’s Bug of the Week feature.

Following a brief romantic interlude, the female cicada killer wasp digs a finger-sized nesting chamber in the ground, leaving telltale piles of excavated soil.

Then she climbs trees in search of the cicadas which she uses to feed her young. 

When she finds a cicada, she stings it to paralyze it, then flies the cicada down to the ground, dragging it to her nest. This is no mean feat since cicadas are much larger than she is. That’s one determined mama.

She stuffs the cicada into her nest, lays an egg on it, and seals the opening. When the egg hatches, the larva will chow down on the cicada which is, unfortunately, still quite alive. Ah, the circle of life.

Well fed, the larva will wrap itself in a case, pupate and stay underground before emerging as an adult next summer. 

Interestingly enough, female cicada killer wasps can choose the sex of their babies. If they give them one cicada as food, they turn out to be boys. Given two cicadas, they become larger females.

A female cicada killer wasp’s work is never done. As soon as she seals one nest, she makes a new one and goes cicada hunting again, helping to keep their population in check.  

See female cicada killer wasps in action in this Bug of the Week profile.

Cicada killer wasps also are good pollinators, moving pollen from plant to plant as they feed on nectar as adults.  

Cicada killer wasps congregate around some petunias.
Photo: John Lefebure

What should you do if you find cicada killer wasps in your yard? Not a thing. Tolerating them is best since they’re only around for a few weeks and are beneficial. Chemical controls are not necessary.

But if you’re bothered by the holes they make in your lawn, wet down the area with a sprinkler.  Cicada killer wasps don’t like to build nests in moist soil.

They also avoid nesting in dense lawns. So their nests are a clue that your lawn may need some beefing up.  

Cicada killer wasps may be big and a little scary looking. But I hope you’ve gained some appreciation for these fascinating insects and enjoy watching them dance over your lawn.  

By Annette Cormany, Principal Agent Associate and Master Gardener Coordinator, Washington County, University of Maryland Extension.

This article was previously published by Herald-Mail Media. Read more by Annette.


Insects: Our Most Under-Appreciated Neighbors

Why should I want bugs, insects, and creepy crawlies in my yard or green space?

Insects are an incredibly diverse group of organisms, with 91,000 described species in the United States and likely an equal number yet to be described by scientists. Only an exceedingly small fraction of these species ever have negative impacts on humans as “pests” (<1% of species). Often the overabundance of pest species is due to human agricultural and landscape practice choices. The vast majority of insects in shared spaces with humans like yards and parks are going about their own lives. In addition to being fascinating creatures deserving of habitat in their own right, they also often contribute to unnoticed but very important tasks that help humans, termed “ecosystem services.” The next time you see one of these critters in your yard, consider thanking them rather than smashing them.

What are ecosystem services?

Ecosystem services are benefits that humans gain from the environment. Examples of ecosystem services include water filtration, raw material production, erosion control, and pollination. Some ecosystem services, like the maintenance of atmospheric gasses (e.g. plants remove carbon dioxide and produce oxygen that humans breathe), are noticeable and directly impact our everyday lives. On the other hand, services like decomposition may go unnoticed because they indirectly affect us.  

Insects (and their arthropod relatives like spiders and earthworms) play vital roles in many ecosystem services. This is often due to insects interacting with plants in some way, though insects also provide food for many other animals. Below are some examples of the ecosystem services that insects contribute to.

Water filtration

Filter-feeding insects positively affect water quality because they remove particles of dead organic material. Insects retain many of the nutrients they filter out of the water, thus reducing the likelihood of algal blooms, their associated toxins, and dissolved oxygen “dead zones.” This is crucial because clean water provides habitat for other plants and animals like fish and amphibians. It also means less effort is required to purify water for human use. 

Types of insects that improve water quality:

  • Blackflies, mayflies, stoneflies, and caddisflies (Note: the underlined insect groups are not “true” flies in the taxonomic Order Diptera; they are part of other orders.) 

Other types of organisms that improve water quality:

  • Mussels, crayfish, snails

More information: Why Care About Aquatic Insects


Biocontrol is when natural enemies are used to suppress pests and reduce the amount of damage they cause. Natural enemies are insects that are antagonistic to pest insects. There are three types of natural enemies: predators, parasitoids, and pathogens. Preserving natural enemy populations is crucial to reducing our reliance on pesticides because when natural enemies are active, pest outbreaks are less likely to occur in the first place. Predators need food all year, so they also need alternate prey available in order to prevent pest outbreaks. Pesticides eliminate beneficial insects in addition to pests, so they should be used only as a last resort.

Fun fact: Fireflies spend much of the year as larval predators belowground, feeding on pests like grubs in turfgrass yards. If no prey is available in yards, then there will be no display of adult fireflies in the summer.

Types of insects used for biocontrol:

Other types of organisms used for biocontrol:

  • Fungi, birds, amphibians, reptiles, and mammals

More information: Approaches to the Biological Control of Insect Pests.

Seed dispersal

Seed dispersal is when seeds are moved away from the parent plant. Seeds are moved when insects knock them off while feeding or when insects collect and then move seeds to a new location. Seed dispersal is important because it reduces resource competition between the parent plant and offspring plants. It also makes germination and seedling survival more likely, especially in arid climates. 

Types of insect seed dispersers:

  • Ants (most effective), beetles, wasps, thrips, and some moths

Other types of seed dispersers:

  • Fruit-eating animals (frugivores), such as some monkeys, lizards, and bats
  • Unwitting animal dispersers of sticky seeds like this

More information:

Seed Dispersal – The Australian Museum

The Conservation Physiology of Seed Dispersal

Decomposition & nutrient cycling

Nutrient cycling and decomposition are two important processes that rely on one another. Nutrient cycling is when soil nutrients are taken up by plants, insects eat plants, and then those nutrients are reintroduced into the soil when dead insects and droppings are broken back down into nutrients via decomposition. Decomposer insects help clear dead animals and plants off the ground which would otherwise accumulate everywhere. They also help create soil texture and circulate nutrients back into the soil, which plant populations and productivity depend on.

Types of insect decomposers:

  • Many beetles, springtails, termites, wood cockroaches, and some fly larvae (maggots)

Other types of decomposers:

More information: Decomposers

Supporting food webs

Insects are a main source of protein and nutrition for many animals (and even some plants). They play a crucial role in transferring energy from plants to larger animals that eat insects like spiders, birds, frogs, fish, bats, foxes, opossums, and bears. This wide food base that they provide allows for functioning, stable ecosystems that are resilient to disruptions.

Fun fact: By weight, there are roughly 300 times more insects than humans on Earth.
There are so many animals that eat insects, but here are just a few examples:

  • Terrestrial bird species, in particular, feed their babies almost exclusively with insects, and if there are fewer insects, baby birds are less successful at fledging from nests.
  • Popular fish like salmon, bass, and trout eat insects, especially when they’re young.
  • Grizzly bears will eat tens of thousands of moths a day to prepare for hibernation.


Pollination is the transfer of pollen between flowers, resulting in flower fertilization and seed/fruit production. It is an unintentional consequence of pollinators going from flower to flower to feed themselves. Pollination is crucial for human survival, as 80% of plant-based foods and products rely on animal pollination. According to the USDA, pollinated crops are worth $18 billion in the US alone. Foods requiring pollination include apples, blueberries, chocolate, coffee, grapefruit, peaches, peppermint, sugarcane, tequila, and vanilla. 

Fun fact: beetles were likely the first insect pollinators– starting 200 million years ago!
Types of insect pollinators:

  • Bees, wasps, beetles, flies, ants, butterflies, and moths

Other types of pollinators:

  • Birds and bats

More information:

Pollination Basics

What is Pollination?

Why is Pollination Important?

Pollinated Foods

By Yasmine Helbling, Kelsey McGurrin, and Karin Twardosz Burghardt, from the University of Maryland Department of Entomology, Burghardt Lab

And the Pollinator Prize Goes to… Hoverflies!

We hear a lot about pollinators these days, but most of the attention appears to always go to one group of them: bees. However, the diversity of pollinators expands way beyond this one group of insects, as we discussed in a previous post. In today’s post, I want to bring the spotlight to one of those non-bee pollinators, which I always feel stay in the background of our pollinator discussions and are massively underappreciated, despite their important role in our ecosystems. Come with me to give hoverflies the recognition they deserve.

What are hoverflies?

With over 100 species in Maryland, hoverflies (sometimes also called flower flies, or simply syrphids) are a group of flies that belong to a family of insects called Syrphidae. They are called hoverflies because they are very good fliers, able to quickly change directions or maintain their flying positions in very impressive ways. While their larval stages can have a huge variety of nutritional needs (some of which make them great biological control agents of pests), a very large number of the species are strongly associated with flowers as adults. In fact, the females require nectar and pollen consumption for their ovary development, making them depend strongly on floral resources for reproduction. For this reason, they act as important pollinators of many wild plants and crops, especially in temperate climates. Although not fully recognized by the general public, pollinating hoverflies have been shown to contribute globally to the pollination of over 70% of crops globally and about the same percentage of European wildflowers (few studies have evaluated the latter in North America)! You can learn more about this in this recent publication.

Hoverflies can be recognized by their large eyes, short antennae, and at rest their wings positioned perpendicularly to their body, as seen here in this (likely calligrapher or Toxomerus) hoverfly from Maryland. Photo: A. Espíndola

Ecology and biology of hoverflies

I hope that you’re now starting to get excited about these little creatures. Before you run outside to try to catch a glimpse of them, let me tell you some more about their lives, so you can continue to be amazed at what they do and why I am on a “pollinator recognition” mission for them.

As I was saying before, a vast majority of hoverflies are strongly associated with flowers. This makes them potentially important pollinators, and this is indeed true for many of them. However, there’s another reason why they are so important: their ecology. In fact, hoverflies have migratory or at least long dispersal behavior. This means that they have great potential for long-distance dispersal of pollen, and thus can contribute strongly to the pollination of plants that may be spatially far away from each other. Thinking about pollination and its role in plant reproduction, such long-distance pollen dispersal can be key in the reproduction of isolated plant populations, and even in increasing and maintaining genetic diversity in those populations. All of that tends to positively impact the ability of those plants to maintain their populations, making hoverflies key actors in sustaining the diversity of many wild plant species.

And also, because I really want to make an impression on you 😊, know that when I talk about hoverfly migration, I am talking about migration patterns that can in some cases be equivalent to those of more “famous” insects, such as monarchs. Some studies have shown some hoverfly species migrate thousands of miles, following the seasons. Although this is relatively well-studied in Europe, we know that similar migration patterns also occur in other parts of the globe, including North America. And as a fun fact, in our research group at UMD, we believe that we once observed and sampled a wave of migration of hoverflies right here, while studying pollination interactions in the endangered serpentine grasslands of Maryland.

a fly that looks like a bee with large black eyes

a syrphid fly that looks similar to a bumblebee

a syrphid fly has yellow and black stripes and two wings
Hoverflies often trick us into thinking that they are something they are not. Here we have some great examples of elaborate mimics of bees/bumblebees and wasps. Can you spot the traits that give them away? Top: Bare-eyed bee mimic (Mallota bautias); center: Hairy-eyed bee mimic (Mallota posticata); Bottom: Transverse-banded flower fly (Eristalis transversa). Photos T. Shahan, M. Wills, J. Gallagher. All CC.

How to recognize them?

Perhaps a reason why hoverflies are underrecognized is that many of their species display impressive body mimics of other species, many of which people tend to be afraid of because of their stingers. For example, some of the most common hoverflies in our area display yellow and black stripes, tricking us (and potential predators) into believing they are in fact wasps or bees. This is a strategy that protects them from predation but also requires us to be more attentive when we are trying to find them.

Despite this, there are some simple ways to recognize their trick. Because they are flies, hoverflies have characteristics that differentiate them clearly from other groups of insects, such as wasps. One of the main traits to look for when trying to figure out if we are facing a hoverfly (vs. a wasp, for example), is looking at their wings. Unlike bees and wasps, flies have only one pair of wings, which at rest they usually extend perpendicularly to their body, which makes them look like a plane or a “T”. Wasps and bees, on the other hand, typically don’t do this, and they fold their two pairs of wings flat over their abdomen while they are at rest.

Another way to tell them apart from most other wasps and bees is their heads (this may be also useful when the wing trait is not easy to see). In fact, flies generally have VERY large eyes (just think about any fly costume 😉). Hoverflies are no exception! They also have large eyes that cover a very large part of their heads, as well as very short antennae. On the other hand, bees and wasps, usually have much much longer antennae that extend way beyond their heads.

Ready to go out and find some of them? Remember that you can always check out iNaturalist to help you out with identifications! Good luck!

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,, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

Are Baldfaced Hornets Friends or Foes?

Distinctive white marks on their heads give baldfaced hornets their name.
Photo:  Johnny N. Dell, Bugwood

It’s been a good year for baldfaced hornets. Many people have contacted me to report their grey papery nests in trees or hanging from the eaves of their homes.

So, are they good guys or bad guys? Do they need to be controlled? It’s a matter of making an informed choice. So here are the facts.

First, baldfaced hornets aren’t hornets at all. They’re black and white yellowjackets that nest in trees, shrubs, and on buildings. Since they kill many harmful pests, they are considered beneficial.

It’s only when their nests are nearby that they pose a potential threat from stinging. Left alone, they tend to be benign. They usually only sting to defend their nests. I’ve had several walk up and down my arm peaceably. 

The white marks on their head earn them their “baldfaced” moniker. Workers measure about three-quarters of an inch long and queens are slightly larger.

In the spring, overwintering queens emerge from tree bark, stumps, logs, rock piles, and other protected spots. Each queen builds a small nest with a few brood cells, lays eggs, and gathers insects to feed the growing workers.

When those workers become adults, they take over the housekeeping duties, building and taking care of the nest, foraging for food, and tending to the growing family from eggs laid by the queen.

Baldfaced hornets’ football-shaped nest is an engineering marvel. To that first handful of paper cells, workers add layer upon layer of hexagonal combs similar to those of the honey bee.

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Non-Native Plants Support Non-Native Mosquitoes

It is a common misconception that all mosquitoes feed on blood. Unlike ticks, which require a bloodmeal to progress from one life stage to the next, mosquitoes largely rely on plants throughout their life cycle. Only adult female mosquitoes bloodfeed in order to acquire protein to lay eggs; otherwise, adult mosquitoes feed on plant sugars to gain energy for flying, mating, and metabolic demands. Once those eggs are laid in standing water, mosquitoes hatch as aquatic larvae that eat microbes supported by decaying organic matter, called detritus. This detritus often comprises plant parts like leaves, seeds, and fruits that fall from nearby vegetation into larval habitat. The next life stage before adulthood, the pupa, is non-feeding, so the amount and quality of detritus mosquitoes receive as larvae are crucial. Just like we tell children to drink their milk to grow up to be big and strong, mosquito larvae with plentiful and nutritious resources can reach adulthood faster, grow larger, live longer, and lay more eggs as adults. Yikes! 

life cycle of a Aedes mosquito from adult to egg to larva to pupa
Aedes mosquito life cycle.
Image credit: Centers for Disease Control and Prevention

Leaves may vary drastically in their chemical composition, affecting which microbes they support, how quickly they decay, and what beneficial nutrients or toxic secondary metabolites they release as they decompose. Researchers are still working to identify important traits in a detritus resource base, but a trend has emerged: non-native plants seem to support non-native mosquito populations better than native plants do.

Native species, whether plant, animal, or microbe, are those that occur naturally in the region where they evolved. Over the course of time, these species have adapted to the local environment and developed relationships with other native species. Conversely, non-native species are those which evolved in a different region from that in which they can now be found. A small percent of non-native species establish and spread rapidly throughout their new home, with the potential to harm human well-being, environmental health, and/or economic prosperity. Some researchers speculate that non-native species share certain traits that make them successful invaders. The Asian tiger mosquito, Aedes albopictus, is one of the most successful invaders of the past century, arriving in Texas from Asia in 1985 and reaching us here in Maryland by 1987. The tiger mosquito is capable of spreading viruses such as dengue, West Nile, and zika; it is also a nuisance vector, driving people indoors with its aggressive daytime biting behavior. 

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Moths in the Landscape

 The best kind of green thumb…a perch for a Luna Moth. Photo: M. Talabac

Q:  I found a huge green moth on my front door! What is it, and do they visit flowers so I can attract more?

A:  This beauty is one of my favorite insects…a Luna Moth, a native species and one of our largest North American moths. Their green color, rare among our local moths and butterflies, ranges from medium to pale celery-green or a pistachio ice cream hue. Their long hindwing tails and eyespots combine to give them a look resembling an elephant’s face. I imagine those eyes give foraging birds a moment’s pause, though the bigger predator for these moths is probably bats since they are night-flying.

Adults have vestigial mouthparts and cannot feed, so flowers won’t attract them. They rely on body fat stored from the caterpillar stage (which grows gleefully big) to fuel their brief search for mates and egg-laying sites. You can support breeding populations by caring for caterpillar host plants, which for Luna include hickory, walnut, sweet gum, and white oak, among other trees.

Avoiding pesticide use in home landscapes is of critical importance, though communities that are subjected to aerial forest sprays for Spongy Moth or other pests may, unfortunately, experience population declines, even though such treatments are relatively targeted. Gardeners attempting to rid a tree of nuisance aphids, Spotted Lanternfly, scale, and other insects could inadvertently affect harmless species like these moths in the process. Remember that any tree roots infiltrating a lawn that is treated with a systemic insecticide (like for grubs) might absorb some of those chemicals and transport them into the canopy.

Light pollution is another big detriment to these and many night-active insects (like fireflies), with home landscape accent lighting, porch lights, street lights, and other sources of illumination interfering with their ability to navigate at night.

For anyone curious about moths, I encourage you to participate in or follow National Moth Week, a citizen science project taking place the last full week of July each year. Check out what visits your porch lights, flowers (there are some day-flying nectar-feeding moths), and see if you can ID the caterpillars that wander the landscape or chew holes in tree, shrub, or perennial leaves. So few are truly pests so you won’t need to worry about managing them; leave them to fulfill their part in the food web of our local ecosystem.

You can also sign up to learn about nighttime pollinators and how to support them in the upcoming free webinar: “Working the Night Shift: Pollination After Dark,” taking place on August 3 from noon to 1:30 pm.

By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.

Have a plant or insect question? The University of Maryland Extension has answers! Send your questions and photos to Ask ExtensionOur horticulturists are available to answer your questions online, year-round.