Pollinators – Maryland Grows

Enhance Biodiversity in Your Vegetable Garden by Planting More Flowers!

May 28, 2026Maryland GrowsLeave a comment

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.

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!

Book Review: The Nature of Oaks

January 15, 2025January 15, 2025Maryland GrowsLeave a comment

Winter’s leafless landscapes, while beautiful in their own right, can look barren compared to the cacophony of color and activity of late spring/early summer. Once an oak’s leaves have senesced and its acorns have fallen, you’d think that not much is happening way up there in the canopy. But surprisingly there is! Tallamy’s The Nature of Oaks, takes the reader on a month by month journey of how these mighty trees support an abundance of life year round.

In fact, indigenous oaks (genus Quercus) support the highest number of Lepidoptera (butterflies, moths, and skippers) species in the mid-Atlantic region- some 534 different native species (Tallamy & Shropshire, 2009). Lepidoptera in the larva or caterpillar stage, such as the Greater Oak Dagger Moth (Acronicta lobeliae) (Fig. 1), often have a narrow diet breadth feeding on only a single family of plants. The over 500 species of caterpillars that oaks support, in turn, feed birds and other wildlife further up the food chain.

Fig. 1. Greater Oak Dagger Moth caterpillar. Photo: Nick Furlan

Tallamy’s Nature of Oaks gives numerous examples of insects’ impressive camouflaging, and describes how it helps them go undetected by hungry birds. For instance, the oak specialist American Oak Beauty (Phaeoura quernaria) blends in amazingly well with its host plant during both its larval and adult stages (Figs. 2 & 3). It’s no wonder that we often don’t notice all of the activity on oaks, especially given that much of it takes place at night.

Photo of an American Oak Beauty caterpillar on a tree twig. The caterpillar looks very much like the tree twig. — Fig. 2. American Oak Beauty caterpillar. Photo credit: Adrian Romo

Photo of an American Oak Beauty moth on the bark of an oak tree. The bark is covered with gray and green colored lichens. The moth's body colors and color pattern make it difficult to see the outline and shape of the moth. — Fig. 3. American Oak Beauty moth. Photo credit: Basil Conlin

Tallamy also considers what’s going on beneath the canopy. Many oak-dependent species complete their life cycle in either the leaf litter or soil at the base of the tree. Research by our state entomologist and UMD alum Max Ferlauto shows that raking less results in more butterflies, moths, and beneficial arthropods. The harmful effects of leaf removal are widespread, impacting community composition, nutrient cycling, and soil stability (Fig. 4).

Illustration showing the negative effects of removing leaves from the ground. — Fig. 4. Negative effects of leaf removal. Illustration by Maggie Lin

Of course oaks support a host of other arthropods and critters- from tiny wasps that form galls on oak leaves and terminal buds to numerous birds and mammals that depend on the trees’ nutrient rich acorns. Tallamy’s Nature of Oaks contains compelling data and entertaining anecdotes that left me awestruck by the beauty and interconnectedness of these mighty trees with all living things. Tallamy suggests if you can only plant one tree, make it an oak.

If you’re feeling inspired to plant an oak in your yard, Tallamy provides guidance on where and how to plant oaks for long term success. For instance, to overcome the concern of tree damage, he suggests planting young trees closer together (vs a specimen tree) so that they’ll be smaller in diameter and their roots will interlock. In Maryland, we’ve 21 native oak species that are commercially available, including two that reach a max height of 20 feet. For photos and details on growth requirements, habitat value, etc. see the new Commercial Maryland Native Plant List.

Where can you purchase native oaks (and other plants)? This month, the MD Department of Agriculture (MDA) launched a certification program for wholesalers, growers, and retailers of native plants. The program will make it easier for consumers to find sellers via a tiered system (novice, pro, and premium). Certified sellers will be listed on MDA, MD DNR, and UME’s web sites (coming soon). The program will also help consumers quickly identify which plants are native to MD via a new ‘Best Maryland Native Plant’ logo that retailers are encouraged to use on plant tags and signage.

If you’ve any questions or comments about growing or using oaks or native plants in general, I’d love to hear from you at lkuder@umd.edu.

Reference:

Tallamy, D. W., & Shropshire, K. J. (2009). Ranking lepidopteran use of native versus introduced plants. Conservation Biology, 23(4), 941-947.

By Lisa Kuder, Native Plants and Landscapes Specialist, University of Maryland Extension. See more posts by Lisa.

How to Pay for a Pollinator or Native Plant Garden?

December 9, 2024Maryland GrowsLeave a comment

We hear a lot about the importance of establishing native and pollinator gardens. Indeed, these spaces provide many ecological services, from providing food resources and shelter for biodiversity to improving the quality of our soils and reducing water runoff. However, establishing these spaces requires at least some funds, which may or may not be available to many. In this post, I want to share some resources that can provide either funding or materials to establish such spaces in our properties.

Grants and rebates for native gardens and more

In our region, several grants exist that can provide funding to partially or completely cover expenses associated with the establishment of pollinator and native gardens. Some of these are state- or region-wide, while others are county or city-based. Below I share some of these, but because many of these grants are local, if you don’t happen to be in the regions where these are active, do a quick search on your favorite web search engine and I am pretty sure you’ll find one that applies to you relatively easily.

State-wide grant:

The Chesapeake Bay Trust has a state-wide program of mini grants which can be used to fund pollinator and rain gardens, among others. These grants provide up to $5,000 of funding for projects of different sizes, and the submission deadline is on a rolling basis. Applicants can be many different types of organizations, but it’s best is to check their current guidelines to know all the specifics about each year’s rules (these can be found directly on the grant website).

County-based programs:

Log for Prince George's County. It says Prince George's County Maryland Proud. Get to Know Us.

The Rain Check Rebate Program is offered by Prince George’s County and includes monetary support to establish rain gardens (which can also act as pollinator gardens) and other features (e.g., rain barrels, permeable driveways) that will increase water retention and reduce water runoff. Through this program, private property owners receive up to $6,000, and commercial properties, associations, and non-profits receive up to $20,000. The application process is relatively straightforward and simple, and the reimbursements are processed relatively quickly.

The non-profit Unity Gardens provides grants to fund the planting of native gardens (including rain and pollinator gardens) in Anne Arundel County. These grants are open to the public and range from $1,000 to $3,000 (depending on the type of project). Applications open in the fall and spring, but the documentation and guidelines for applications are accessible all year round. Check the website to learn more.

City-based grants:

The city of Ocean City, MD offers mini-grants for local property owners. These grants aim to support the establishment of pollinator gardens and other native plant gardens within the boundaries of the city. The grants provide up to $5,000 of funding, and applications for some of these projects are open year-round, while others have specific deadlines. Check the grants website to learn the specifics about each of these programs.

Free plants to establish gardens

Not every organization or institution has funds to establish grants such as those presented above. However, many cities and other non-profits give away plants at different times of the year. Generally, these giveaways happen in the spring and the fall, when plantings are the most likely to succeed. Below, I’ve included some examples for you. However, note that many local events happen everywhere, so if you’re interested in these giveaways, I strongly recommend that you search or keep an eye out for announcements in your area by the end of the winter or the summer.

Free native garden kits and plants:

The organization Nature Forward provides free native garden kits which include garden designs and the actual plants that go with them! Because this is directly associated with the Anacostia watershed, the geographical range of this program is restricted (check the map on their website). The sign-up is currently full, but you can still add yourself to the waitlist.

Sometimes, native plant nurseries decide to organize such giveaways. This is the case of Bona Terra in Friendship, MD, which created a “plant grant,” basically a registration-based plant giveaway. The giveaway can be for individuals or groups, and registration is required to receive either individual plants or trays. Check out their website to learn more and access the forms.

City-based plant giveaways:
Several cities provide free plants to their residents. An example is the City of College Park, which has been giving away native plants that support pollinators throughout the year at markets and public events. Check with your city or local government to see if such programs are available to you… and if they are not, you can always ask for them to be established!!

How to Help Overwintering Pollinators

September 27, 2024September 18, 2024Maryland GrowsLeave a comment

Raise your hand if you want to help butterflies, bees, and other pollinators. Good for you.

In my last blog post, I discussed two ways to help pollinators starting in the fall. Waiting to cut back perennials until spring and letting some leaves lie protects overwintering insects.

But there is so much more you can do to help this fall and year-round. It’s all about creating habitat, providing safe spaces for pollinators to live, eat, shelter and raise young.

My neighbors raised their eyebrows when I plunked a moss-covered log into my landscape. But it looks terrific in my woodland garden, a natural accent that provides shelter and food for wildlife.

*Logs are attractive habitats for wildlife, including pollinators. Photo: Annette Cormany*

So, adopt a log. Spiders and beetles are attracted to the moist areas under logs and peeling bark. Bees and butterflies nest and overwinter in drier parts of logs.

Logs help other wildlife, too. Chipmunks use them as highways, toads love their moisture, and other critters use them for sunbathing.

Lay logs horizontally, burying one end a few inches to maintain some moisture. And be sure to ask permission before tossing that log into your pickup. Mine came from a family property. Honest.

Dead-standing trees called “snags” also provide habitat for pollinators and other wildlife. As long as a tree poses no danger to you or your home, consider leaving it. What looks messy to us is beautiful to wildlife.

Beetles and other insects burrow through dead wood, creating tunnels that cavity-nesting bees such as mason bees lay their eggs in. Other insects tuck under bark. I once saw a striking mourning cloak butterfly emerge from the bark of a dead tree.

If leaving a whole dead tree is too much for your sense of order or safety is an issue, fell the tree but leave the log in part or whole. Or leave just the stump. Hardwood logs with the bark attached add more varied, longer-lasting habitat.

*Stumps offer food and shelter to insects. Photo: Annette Cormany*

What else can you do to enhance your habitat for pollinators beyond planting native plants that flower from spring to frost? Plenty.

Add a rock pile or wall. Bumblebees, leafcutter bees, and wasps nest in their cavities. Ground beetles and many other insects shelter where soil meets stone.

*Stone walls – including this handsome one dressed in lichen – provide shelter and nesting sites for wildlife. Photo: Annette Cormany*

Use different sizes and types of rocks and skip the mortar to create more protected nooks and crannies. Planting native plants nearby makes the area even more attractive to pollinators and other beneficial insects.

Thanks for all you are already doing to help support and protect pollinators. It matters.

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.

Community Partnerships for Pollinators

September 9, 2024September 9, 2024Maryland GrowsLeave a comment

When we talk about pollinators and how to help them, we have often focused on what plants can support them, who the pollinators are and some traits of their natural histories, or how to create habitat for them. However, besides individual actions that people can take to help them, other options that are very impactful also exist. In today’s post, I want to present one that involves a combination of community and institutional collaboration: the Bee City and Bee Campus USA certification.

What are Bee City and Bee Campus USA?

The certifications called Bee City and Bee Campus USA are labels that cities and campuses, respectively, can receive from the Xerces Society if they commit and act to protect pollinators and their habitats.

For those who have never heard of it, the Xerces Society is an organization interested in the conservation of invertebrates and their habitats. Over the years, it has not only become recognized as an important conservation organization but also has developed impactful and meaningful ways to support research on the topic and engage the population and institutions (and many other stakeholders!) in conservation actions that are within their reach. The Bee City and Bee Campus certification is one of those initiatives.

How does it work?

Once cities and campuses decide to receive the certification, they need to submit an application and pay an annual fee. By doing this, they commit to taking specific actions that will lead to the conservation of the thousands of species of bees and other pollinators that exist in the USA, as well as their habitats. The certification is revised every year, and if the institution or city is not performing following the set standards, the certification is not renewed. Today, many institutions and cities across the USA have joined the initiative and are actively following their commitments. If you are interested in knowing if your community is a part of the initiative, an online database exists where it is very easy to search for participating members using addresses or names.

*The Bee City and Bee Campus USA website has a neat tool to search for current members across the USA.*

The commitments that institutions and cities make when they join the initiative involve the establishment and promotion of specific actions. These actions combine institutional and community involvement, which requires the creation of an active committee that will be responsible for running programs that will help the institution reach its goals. Once this committee is created, the group is responsible for proposing and running actions within the reach of the institution. The actions need to be oriented towards promoting the protection of pollinators and their habitats through what can be generally categorized under education, direct action, community involvement, and potential revision of standard operating procedures or policies.

The Xerces Society doesn’t just provide a certification. In fact, it has over the years produced a massive number of tools that help cities or institutions understand how to run the programs. Regular webinars are organized, fact sheets distributed, general manuals and other documentation shared, and a network of participating cities established, allowing for a “hive mind” to develop.

What can some of these actions be?

Education programs involve the distribution of information among the population (for cities) or members of the campus (for campuses). This information can take many different forms but generally educates about the diversity of pollinators, the importance of promoting habitat, the key contributions of pollinators to the well-being of the community and the environment, ways to protect them through individual or joint actions, creating information guides and fact sheets, and more.

Direct actions often require involvement of the institution in establishing habitat for pollinators, distributing resources that will allow the community to protect pollinators (e.g., distributing plants, seeds, other habitat resources), actively reducing the use of pesticides, etc.

Community involvement is promoted by any program that the institution could build to allow its members to come together and engage in projects larger than any individual would be able to take on by themselves. There are many ways this can be done, but some examples are the creation of student-faculty groups that could run research projects that can then be used to inform policies and conservation actions. Others could be the establishment and promotion of institution-wide actions, such as the promotion of months with no or reduced mowing (e.g., “No-Mow Month” initiatives), the running of citizen science projects (e.g., through iNaturalist), establishing days centered around the celebration and recognition of pollinators and their services to humans and the environment (e.g., coordinating Pollinator Week activities), and others.

Finally, one of the unique reaches of this initiative is its ability to promote changes of policies and procedures regularly used by the institution/city. Under this program, the committee should propose and the city or campus implement at least some adjustments in the way the institution in question is run. For example, Integrated Pest Management (IPM) plans should be created and used if they are not already in practice, Code can be adjusted to facilitate the planting of native plants, monetary or other incentives can be offered for the creation of pollinator habitat, and more.

I would like to have my city/campus join; what do I do?

If you’re interested in having your campus or city join the initiative, first go to the Bee City/Campus website and check out the requirements and some of the how-to webinars. Along with this, for cities, you may want to get in touch with representatives and present this as a request. If you’re on a campus, get a diverse group of members together and propose this to leadership. If you still feel overwhelmed by this and feel you still have a lot of questions, reach out to Bee Cities or Bee Campuses in your area and ask them for help! They will be more than happy to explain what their path was and how they came to be, so you can also become part of the national initiative.

How to Protect Pollinators in the Fall

August 23, 2024August 19, 2024Maryland Grows2 Comments

Did you know that how and when you cut back your perennials and tidy your landscape matters to pollinators?

I just read a fact sheet from the Xerces Society that opened my eyes to more ways to help pollinators year-round, especially in the fall.

I already make sure I have something blooming from April to frost, so pollen and nectar are always available. And I emphasize native plants that coevolved with pollinators to support them best.

But beyond flowers, there are many things we can do to provide shelter for nesting and overwintering pollinators. And we can start some of them in the fall.

Pollinators and other insects shelter in stems and branches of trees, shrubs, and flowers. They also shelter in leaf litter, undisturbed or bare ground, dead wood, brush piles, and rock piles.

Incorporating these features in your landscape – rather than cleaning them away – supports bees, butterflies, and other pollinators.

So how can you make your garden more welcoming to pollinators this fall?

Start with the stems. Don’t cut back your perennials until late spring. Bees and other pollinators hibernate in the stems in winter. Only remove unhealthy plant stems to manage disease.

But doesn’t that look a little unkempt? Yes, but messy is beautiful – and necessary for pollinators to survive and thrive.

*Master Gardener sign explaining why a messy garden is good for pollinators*. *Source: A. Cormany*

The Master Gardeners and I believe this so strongly that signs in our teaching gardens say, “Excuse our mess, pollinators at rest,” to explain why we don’t cut back plants in the fall.

Next, leave some leaves. Most butterflies and moths use leaf litter to protect eggs, caterpillars, chrysalises, or adults over the winter.

Wooly bear caterpillars tuck into leaf piles. Luna moths wrap their cocoons in leaves. Some butterflies lay eggs on fallen leaves. Queen bumble bees burrow into soil under leaves.

A luna moth cocoon wrapped in leaves to wait out the winter.
Photo: M. Raupp

So pile some leaves around trees, shrubs, and perennials as a natural mulch. They will suppress weeds, hold moisture, and feed the soil. I chip some leaves but leave some whole.

I often use leaf mulch in my vegetable garden, too. And when I had a larger landscape, I kept a 3-foot border of leaves against a stone wall to provide more shelter.

Leaves aren’t litter: they’re habitat. Ideally, some leaves will become a permanent part of your landscape. Pick a corner, an edge, or a garden. I let leaves lie in a small woodland garden.

But if you need to remove some of the leaves, try to leave them in place until mid-spring to give overwintering pollinators a chance to emerge.

This is really a glimpse of the many ways you can invite and support pollinators year-round. Learn more about Pollinator Gardens on the Home and Garden Information Center website.

Thanks for all you are doing to protect pollinators. It matters.

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.

Heat Waves Affect Pollination Too

August 5, 2024March 7, 2025Maryland Grows2 Comments

Having grown up in the plains of Argentina, surrounded by large rivers, swamps, hot summers and humidity, I can attest that I am pretty “heat tolerant.” While others complain of the heat, I just enjoy the “embrace” that a hot day gives me. The heat in the last few weeks, however, was even too hot for me! And while I was trying to cool down, I was also worrying about what I was seeing outside: the plants, the insects, the soil… all suffering like me. And because I happen to work on some of these topics, I also knew that it wasn’t just that some plants were drying out; this heat wave (and drought) is also affecting the whole network of interactions that happen around us. So, today let me tell you a bit about how these extreme heat waves affect one of those interactions – pollination – and how what we do in our green spaces can help reduce some of those effects to the benefit of all.

Pollination is affected by heat in more ways than we usually think

Extreme heat waves and droughts such as those we have been experiencing recently affect not only us but also the ecosystems that are exposed to the heat. One of the most evident effects we may see is how much plants suffer. Just look outside and you will see hanging leaves, tiny flowers (if any), and a lot of dry material. As with all organisms, plants also have optimal temperatures at which they can survive; if the temperatures and water availability change, important body functions will not be able to be performed, and even some central parts of their bodies will fail.

In plants, one of those functions is photosynthesis, the process by which plants can make sugar using the energy of the sun, carbon dioxide (CO₂), and water. This process is the way the vast majority of plants make their food. If the process is disturbed, the plant will have less energy available to survive, grow, and reproduce. It turns out that extreme heat and water needs affect the ability of plants to photosynthesize. The consequence of this is that, suddenly, the plant has less energy available, needing to enter a sort of “survival mode.” Along with this, the heat affects several protection systems that the plant has, especially those that protect the DNA (the genetic material), as well as the functioning of the machinery that literally “builds” the different parts of the plant. This inefficient protection leads to the DNA being damaged and the plant being poorly “built”, making that part or the whole plant start malforming.

plants with browing stems due to drought — *During the heat waves, these beebalm plants had a rough time, with almost no flowers produced and a lot of the plant material simply drying out. Photo: A. Espíndola*

In relation to pollination, we know that these changes explain why, under heat and water stress, plants become smaller in size, have tiny or no flowers, lose a lot of leaves and biomass in general, and have parts that start to look “funky.” The changes in the energy availability make the composition of some secretions change as well, such as with nectar, which tends to be less rich in sugars and less abundant (especially when drought is experienced).

a plant with smaller than usual yellow flowers — *These black-eyed Susans were able to make flowers this year, but they are significantly smaller than usual! Photo: A. Espíndola*

As said before, flowers tend to be small or absent, but even when they are present, the petals and reproductive organs are often misshapen, with the plant becoming unable to produce seeds and fruits. Finally, and super importantly for pollination, a major effect of this is that heat affects pollen quality, reducing the amount that is produced and often making the pollen inviable… meaning that even if the pollen was to land on a stigma, it would likely not germinate, and fertilization would not take place. This latter point is worrisome because it means that even plants that are not animal-pollinated (e.g., plants pollinated by wind or water) will be unable to produce seeds and fruits.

Pollinators suffer the heat, and that affects their survival and pollination

Pollinating insects are also affected by the heat, and some of these effects are related to the same facts we mentioned for plants. On the one hand, like plants, pollinators also have their own DNA and “body-building” machinery that is disturbed by heat. Some of the major consequences of this are that their development can be either interrupted (the larvae or pupae die off) or interfered with. If the development is interfered with, we see malformations in different organs, such as the wings, legs and mouth parts, and particularly in males, of reproductive organs and sperm. Further, extreme heat appears to affect bee neurological abilities, with their behaviors and memory affected, as well as changes in the way they visit and manipulate flowers, which in turn makes pollination more difficult.

Along with these issues, because of the changes in nectar quality and quantity associated with plant heat stress that we mentioned earlier, the pollinators’ nutrition is also negatively impacted, which further amplifies the developmental, behavioral, and neurological problems mentioned above. Although all insects experience these types of effects when they are exposed to excessive heat, some of them are a bit better at protecting themselves from it. For example, it seems that social bees suffer less from excessive heat than solitary bees, while bees that nest in the ground or in stems tolerate it better than those that nest in cavities.

Here’s what you can do to help mitigate the effects of heat and drought

Although we can’t instantaneously reduce the heat, we can assist plants and insects to better tolerate these conditions. A very effective strategy is diversifying our green spaces, which can lead to local reductions of heat, either through the shade created by the plants and/or the reduction of the excessive presence of bare soil. In particular, this same plant diversification can also increase the amount and quality of foods available to pollinators during these heat events: more diverse plants mean more different types of possible nectar sources available to pollinators, which in turn would increase their chances of survival and boost their health.

If possible, one can also water plants in our green spaces. By doing this, the water stress will be reduced and at least part of the symptoms displayed by plants will also be mitigated. If one were to do this, it is important to water with a slow flow and for a longer period of time, so the water can properly enter the soil. Along with this, using mulch or letting the fallen leaves cover the ground will also help retain some of the soil humidity, all while also providing shelter to insects.

And besides diversifying and supporting our green spaces, it is thoroughly accepted that the current extreme heat and drought events we are seeing are a consequence of climate change. Starting to reduce our and our communities’ emissions is another way to help plants and pollinators, pollination, and at the end of the day, the production of many of the foods we depend on. You can check out this awesome website by Dr. Sara Via and learn about what we can all do, and even sign up for super informative seminars that help you become familiar with and start acting on some of these topics.