Helping YOUR Local Pollinators: The Problem with Wildflower Mixes, and How to Move Beyond Them

The last month of winter has arrived! Though spring will not truly be sprung for some time yet, many of us are looking forward to the warm sunlight, longer days—and to planting new spring gardens. When the weather starts to change, a young man’s fancy may turn to thoughts of fresh tomatoes ripening on the vine, fruit trees blooming anew each day, or flowerbeds filling with daffodils, geraniums and lilacs.

If you’re passionate about pollinator-friendly gardening and “saving the bees,” you may be planning to fill your garden with a wildflower mix that purports to do just that. Countless online seed and gardening stores sell packets advertised as “bee friendly,” “pollinator friendly” and so on, and frequently tack the word “native” onto these packets as well. Even Cheerios joined in back in 2017, shipping out millions of free seed packets in cereal boxes as part of its “Bring Back the Bees” campaign. However, while these mixes are bought (and usually sold) with good intentions, once planted, they do not always have the intended effect and can even do harm in some cases.

The U.S. is a very large country, encompassing several biomes from tundra to tropical rainforest and containing countless types of habitats and ecosystems. It is therefore very rare for any plant that is native to the U.S. to be native to ALL of it. In some cases a plant species that is native to one region of the U.S. acts as an noxious weed in another. Fortunately this is rare, but it is quite common for U.S. species planted outside of their native range to either fare poorly or simply contribute nothing to the local ecosystem. When seed companies stick the word “native” onto their products, it looks appealing, but that word means nothing without reference as to where the seeds are native.

Another essential fact to remember: most pollinator species have a limited geographical range, as well as a limited number of flower species from which they are specially adapted to feed. For example, hawk moths and certain long-tongued bumble bees drink the nectar of deep, trumpet-shaped flowers, and many non-honey bee species specialize in flowers that require “buzz-pollination”–forceful buzzing to knock the pollen out. With the exception of the incredibly non-picky (and non-native) honey bees and a few select bumble bee and butterfly species, pollinators thrive on flowers that are native to the same area as them—flowers to which they are most adapted.

So, when gardeners plant random mixtures of seeds that are not native to their state or region of residence, the flowers often provide little to no benefit to native pollinators in that region. Widespread ignorance of this fact can result in extensive, expensive planting campaigns that ultimately do little to help. This is precisely what happened with Cheerios’ efforts—once the seed campaign began, journalists and biologists were quick to point out that some of the flower species included were only native to certain parts of the U.S., and some not native to the U.S. at all. The campaign also focused mainly on honey bees at that time, which, though suffering decline, are non-native livestock animals—not to mention that lack of floral resources does not seem to be a major contributor to their decline. Attention to bumble bees, mason bees, sweat bees and other pollinating bee species is sorely lacking in many of these campaigns.

Ultimately, it is crucial to understand what flowers and landscapes are most beneficial to YOUR local native pollinators. But how can one know that? Here’s how you can find out:

      • Research which bumble bee, solitary bee, wasp and butterfly species are native to your region or state, and, if the information is available, which plant species they rely on most for nectar and pollen. If you have a large garden or farm, you might even be able to provide nesting habitat for bees and wasps! Look up the nesting preferences and habits of your local species, and see if you might be able to provide the type of landscape that could support them. (See “Resources” below for easy routes to start this process.)

      • Reach out to local experts! If your state has a university with an entomology department, see if anyone there works in pollinator science and reach out to them for advice. They may be able to tell you which native pollinators are most crucial for the local environment and/or most in need of help, and what you can do to provide resources for these species. Your city or state may also have a native plant society or pollinator initiative group that could provide similar information.

 

RESOURCES:

Saving Native Bumble Bees

In February 2020, a group of bumble bee biologist and conservation professionals gathered at the Minnesota Zoo, in Minneapolis, to work on conservation strategies related to the endangered Rusty Patched Bumble Bee (Bombus affinis).  The meeting, sponsored by the U.S. Fish and Wildlife Service, The Ohio State University, and the MN Zoo, was to discuss if ex situ conservation strategies could be employed to aid in population recovery in the future.  In November 2020 the final report from that meeting was released, facilitated by Kathy Traylor-Holzer of the IUCN SSC Conservation Planning Specialist Group.

Ex situ conservation involves the removal of individual organism from the wild, either for short term activities such as translocation and “rescue” activities, or for longer term programs like captive breeding.  To be sure, ex situ conservation strategies are not a panacea and should be approached carefully and thoughtfully.  At the Minnesota Zoo meeting we met for three days and through a structured workshop, we proposed and considered numerous ideas that had potential as ex situ conservation strategies.  Not all of the strategies we considered came out equal in the end and several are considered risky, or unlikely to create enough benefit toward species recovery to really implement.  Several other strategies have potential.

In the report we discuss some of the benefits of ex situ conservation beyond simply increasing population numbers and that is what I want to cover here.  The particular strategy that I want to explore here for bumble bees is captive rearing of colonies, which I have done a lot of over the years with both common and at-risk species.  While I have never raised colonies of RPBB (Elaine Evans is the only person I know of who has) I think this strategy can teach us a lot.  By rearing colonies in captivity, we have the potential to both increase a population for release, but we also can learn more about the species- its disease stress, nutritional needs, and mating biology, among other aspects of its biology.

Captive rearing colonies

To rear a colony in captivity you have to first catch a queen bumble bee in the wild and bring it into the lab.  Bumble bees need a steady diet of pollen and sugar solution and a warm, dark and quiet location to initiate nesting.  There are many techniques to induce a queen bumble bee to nest in captivity and if the conditions are right the queen will lay a clutch of eggs on a pollen lump and incubate them until they hatch into larvae.  At that point she will incubate them further and feed them more pollen for a couple weeks until they pupate.  For most species of bumble bees about 24 days after egg laying a worker bee will emerge as and adult.  In the lab humans have to provide a steady stream of food as the colony grows and after a few months new queens and males will be produced if the conditions remain good.  Once this happens queens and males are isolated with reproductive individuals from other colonies and allowed to mate before they can be released back into the wild. In some cases, you might choose to keep some of the mated queens in cold storage over the winter and have them establish colonies of their own the next year.

During the colony growth phase, you can learn a lot about the bees, such as how quickly the nest grows, how much they eat, and which diseases they are susceptible to.  There is, of course, a risk that the colonies will not initiate in captivity, or that reproductive output in the lab might be less than the wild, but even these failures can be instructive.  Understanding the conditions that lead to either success or failure of reproduction in the lab can inform management strategies in in field settings as well.

One of the most persistent questions around RPBB recovery is discovering exactly what led to the declines in the first place.  A widely circulated hypothesis is that a pathogen (Nosema bombi) from commercially managed bumble bees spilled over into the wild RPBB populations leading to declines across the range of the species.  While this may be the cause, it has never been definitively shown and the impacts of N. bombi on B. affinis has never been studies.  If ex situ populations can be established, we could investigate the relationship between this pathogen and RPBB either through observing opportunistic infections or through direct experimentation.  Further, impacts of other factors such as diet or climate conditions could be observed in the lab in controlled experiments and provide insights into the decline.

Of course, other strategies are considered in the report and have merit, including translocating queens or male bumble bees to augment wild populations with new genetic material or to reintroduce RPBB in areas where it has been extirpated.  As the report notes, there are many considerations including developing methods to ensure that bees taken into captivity are disease free and that release of captive bees does not move pathogens or parasites to new locations.

A rusty patched bumble bee. Photo credit Tamara Smith, USFWS

This report can help inform the decisions that federal and state agencies make to try to recover RPBB populations.  My hope is that the Strange Lab can continue to contribute to recovery efforts for this species in Ohio and beyond.