Gardening for Native Bees: Interview with Heather Holm
A couple of months ago I heard Heather Holm speak on gardening for native bees at a forum organized by the Lurie Garden. Heather is an award-winning author and widely-recognized advocate and educator for native bee conservation. Educated in Canada, she currently lives in Minnesota. She was nice enough to agree to respond to some written questions for this blog.
Why should native bee conservation be an urgent concern for gardeners?
With the significant amount of habitat loss, we can no longer just garden for ourselves. We have native bees, in particular bumble bees, threatened with extinction or endangered.
How much of a difference can home landscapes make regarding this problem?
Home landscapes can play a significant role in supporting native bee populations, especially if there is a community-based effort of many people gardening or providing flowering plants in a connected corridor in a neighborhood. Native bees are limited in their flight distance and do much of their foraging in a small area if an adequate supply of food is available. They are also adept at finding new sources of food such as the new garden someone just installed. If you plant it, they will come.
In a nutshell, how can gardeners help native bees?
Provide a variety of flowering plants that bloom continuously throughout the growing season, eliminate pesticide use, and provide and protect nesting opportunities for bees.
How do you see the relationship between conservation of native bee species and honeybees?
Apples and oranges. Much is known about the honey bee and the population changes of the honey bee which can be attributed to their domestication (pathogens and disease) and environmental risks such as pesticides. Many people are not aware that the honey bee is a stable species and not at risk of extinction. The media has put too much focus on this one species drawing the public’s attention away from native bees, the bees in need of conservation. Very little is known about population changes of native bees, however, with the exception being bumble bees. One can likely conclude that habitat loss, exposure to pesticides, and climate change are factors also impacting these understudied species.
What is the relative importance of perennials, small trees and shrubs, and shade trees when it comes to native bee conservation?
They are all important. Woody plants including trees and shrubs can play a significant role in providing forage for native bees. Just think of the scale, size, and number of flowers a large insect-pollinated shade tree provides compared to a perennial garden. Creating and maintaining large perennial gardens may not be for everyone so I always encourage people to start with planting trees.
Why are native plants so important to the future of native bee species?
Native plants are particularly important for pollen-collecting specialists (oligolectic) bees which are dependent on, in many cases, collecting pollen from plants belonging to a single genus. Also, native bees have coevolved with a diversity of native plants which historically, would have provided all their nutritional needs.
Many exotic plants seem to be very popular with bees, native or otherwise. Do they have a role in bee conservation in home landscapes?
Yes, exotic plants can attract native and non-native bees. Plants in the mint family Lamiaceae, for example, can provide a good source of nectar for foraging bees and in particular male bees. It is important to remember that the most important dietary component in the food provided for bee larvae is pollen and many exotic plants that get a lot of visitation by native and non-native bees are not necessarily providing all of the critical nutritional components a bee would need. Exotic plants can complement a diverse native planting, helping to ensure a continuous, overlapping succession of flowering plants, or in other words, ensuring the restaurant is always open.
How can gardeners who like an abundant cottage garden style (which abhors bare ground) still make room for ground nesting bees?
I am in favor of covering the ground with filler plants and natural materials such as leaves instead of using wood mulch. It is often stated that native bees need bare ground but many ground nests are initiated under vegetation, not in open bare ground. Heavy layers of wood mulch applied year after year can impede a bee’s access to the ground. In my own garden, I transitioned from using wood mulch for weed suppression over ten years ago and instead let nature provide the natural, ground-covering materials (leaves and plant debris). These natural materials (and a dense herbaceous planting) help with weed suppression but still allow access for bees which crawl underneath the layer of leaves to access the soil. I have seen bees use the exposed soil from edging a lawn as a nesting site too.
What else can gardeners do to help provide nesting opportunities for native bees?
Look for existing ground nests in your garden particularly in the spring before your plants start to grow and cover the ground. If you have existing nests, it can provide you with a lot of information such as preferred soil and exposure. If you find nests, consider how you can provide similar opportunities. For above-ground nesting bees, the majority of which use preexisting cavities, I recommend leaving topped flower stalk stubble (15” tall) from the previous growing season. The other simple thing one can do is incorporate logs on the ground in the garden. Standing dead trees are also beneficial but often not practical for small gardens.
Tell us about your new book, Bees: An Identification and Native Plant Forage Guide. How is it helpful to gardeners?
My new book is a combination of a bee identification guide profiling 30 genera of bees, and a plant library including 100 native trees, shrubs, and perennials that support bees and other pollinating insects. It has a comprehensive listing of pollen-collecting specializations featuring many specialist bees and several of the plants specialist bees depend upon. There is extensive information on the cultural requirements for the plants profiled, as well as pollinator visitation information. Gardeners can use the book in two ways: learn what to plant to attract pollinators, and identify and learn about the biology of the bees that frequent their garden.
Give us a couple of reasons to feel optimistic about the future of native bees.
I am encouraged by the growing movement to garden for wildlife – gardening for ecosystem functionality rather than just beauty. For a butterfly enthusiast, planting milkweed for monarchs may have been the first introduction to floral-faunal connections, for a birdwatcher, perhaps it was purposefully selecting a native shrub which produced fruit that birds devoured in late summer. More people making these connections means we are slowly converting the 40 million acres of useless lawn in the United States into something purposeful and beneficial to bees, birds, and butterflies.