Native bee conservation is near and dear to our hearts. During the past 25 years, our farm in northern Vermont, The Farm Between, has evolved from a diversified farm operation with organic meats, eggs, and fruits and vegetables to an organic fruit farm, and fruit and pollinator plant nursery. Enhancing biodiversity with pollinator and beneficial insect habitat has been a key focus over the years to increase the viability of our farming business while also healing and regenerating the ecosystems that we steward. In this article, we will outline the things that farmers, homesteaders and other landowners can do to enhance native pollinator populations on their land to increase pollination services and their own farm viability.
Many people are aware that honeybees (a “domesticated” bee introduced in the U.S. by European settlers), are stressed due to pesticide exposure, parasites and diseases, and loss of habitat. We love our honeybees, and the stresses are real, but we don’t worry too much about them because they have beekeepers like ourselves to help them along. We can overcome winter losses and support our bees by splitting hives, buying new queens, treating for mites and otherwise adapting our beekeeping practices. While honeybees are an iconic symbol that catches many people’s attention, we joke that ‘Saving the Honeybees’ is like trying to ‘Save the Chickens.’
A more difficult problem is the plight of the native bees and other wild pollinators, because for the most part, they are on their own. Generally speaking, what is good for honeybees is also good for native pollinators, so the not-so-accurate media coverage can be a good thing. Drastically increasing the honeybee population, however, or putting out poorly managed hives in an area can lead to competition for floral resources and parasites and diseases being shared with our native bees. Everything is connected to everything else!
There are around 275 native bee species in Vermont and around 4000 in the U.S. Many of these species are thought to be in decline. The Rusty Patched Bumblebee, for instance, was put on the Endangered Species List this year. In many cases native bees and other wild pollinators are the unsung partners providing pollination services for farm and garden crops as well as native trees, shrubs and wildflowers. Social bumblebees, and solitary bees like the mason bees, digger bees, sweat bees, leafcutter bees, sunflower bees, and squash bees, help keep our farms and gardens bountiful. And they need our support now more than ever.
Two action areas we’ll be highlighting in this article are ideas for creating nesting and overwintering sites, and ways to increase season long floral resources. Another very important practice is to avoid use of pesticides. A good example of a harmful practice is using the class of insecticides known as neonicotinoids (neonics) that are often found in home and garden products and are readily available to homeowners. Neonics are also used on most conventionally grown corn and soybeans as a standard seed treatment. Neonics are systemic pesticides that once applied are expressed throughout the plant, including the nectar and pollen. Even at low concentrations ingesting this nectar and pollen has been shown to interfere with navigational systems of bees, their autoimmune responses, reproductive potential and other aspects of being a bee. These sublethal effects can cause additional stress to already stressed bee populations, so it’s best to avoid them. It is not only neonics that can harm pollinators. We don’t use any pesticides (including organically approved ones, which can be toxic to pollinators too!) because they can potentially impact our native bee populations and have other unforeseen consequences on the ecology of our farms and gardens.
As trained ecologists, we acknowledge how little we humans really know about the short and long term effects of pesticide use on our farm and garden ecosystems. Insecticides, fungicides, and herbicides are all biologically active compounds that can have negative effects on non-target organisms like beneficial insects, soil microbes, and important plant/fungi interactions. We also have little understanding of the effects of pesticides on another complex ecosystem – the human body, but that is another story! Our personal philosophy has been not to use them on our farm and to consume as little as possible of them in our diet.
Our Native Bees and their Nesting Needs
Bumblebees are an example of social bees and are the pollinator workhorses on our currants, gooseberries, blueberries, raspberries and greenhouse tomatoes. They can build up colonies over the summer to as many as 300 bumblebee workers if conditions are good. In the late summer, the original queen lays eggs that will become the new queens and drones. These new virgin queens emerge in the late summer and fall and mate with the drones (ideally from another colony to avoid inbreeding). Only the newly mated bumblebee queens overwinter. The old queen, workers, and drones have all done their jobs and die out before winter.
Towards the end of April here in northern Vermont, about the time the shrub willows bloom, we see the first new bumblebee queens emerge from their overwintering protected places on the farm. They are out and about looking for nesting habitat. Their fat reserves that got them through the winter hibernation will be dwindling and they need nectar for energy. They will be cruising low near rock walls and potential cavities in the ground or in the old hay bales left lying around trying to find suitable nesting habitat. Abandoned mouse nests are a favorite place to establish a colony, so we try to create artificial mouse nests in wooden boxes or by putting hay bales on pallets with rain covers to entice these new queens. Any old mouse nest material found around the farm is put in these nest spaces because bumblebee queens have been shown to be attracted to mouse urine! A queen bee with pollen on her legs means she has chosen a nest site and is beginning to provision it with pollen for her larvae. She collects all the pollen and nectar, makes the waxy brood and honey pots, and incubates the eggs until the first generation of workers emerge in less than a month. After the workers start helping with foraging and brood rearing chores she can stay at home and focus on laying eggs for the colony. Talk about a supermom!
On our fruit farm we generate a lot of prunings from our fruit trees and berry bushes. Some people burn theirs, but we hate the idea of putting all that carbon into the atmosphere when we can put them to use on the farm. We make long piles of our woody scraps and other trimmings, and when they’re about 4 feet tall we cover the pile with a composted manure or barnyard scrapings. The permaculture word for these is hugelkultur (mound culture) and they are known for sequestering carbon and providing long term soil fertility and moisture. We call them bumblekultur because our more open design creates possible nesting and overwintering habitat for bees. Over time, the prunings break down leaving a reduced mound with high organic matter. But for the first several years there are a lot of cracks and crevices that can serve as bee habitat. We grow squash, gourds, other food crops or cover crops like buckwheat and phacelia in the first year, and in later years, perennial and annual flowers. Not only does the three dimensional aspect help for bees’ nesting and overwintering sites, planting on the mound provides additional floral resources. And we’re sequestering carbon. Now, that’s stacking functions.
Solitary nesting bees make up the majority of our native bee species. They live for one season. They lay their eggs in chambers in the ground (ground nesting) or in small tunnels in trees, cracks and crevices in buildings or in plant stems (cavity nesting). Wherever the eggs are laid, the larvae have been provisioned with pollen balls to feed on. Bees are vegetarians and are adapted to collect pollen like nobody’s business (as opposed to their more ill- tempered cousins, the wasps, that are carnivores with a penchant for nectar as an energy source). The solitary bees are generally only out and about as adults for a few weeks in the season. In that short time, the females need to mate with the single minded (some would say shiftless) males, and create the next generation. They work alone to fill hollow stems and tunnels or underground chambers with pollen balls and eggs. Most of their lives are spent as larvae wallowing in a pollen ball in a cozy nest. Depending on the species, solitary bees overwinter as last stage larvae, pupae, or adults. Different species emerge at different times over the growing season and have different plant and nesting preferences. For example, Blue orchard mason bees (Osmia lignaria) emerge in early spring and are especially effective pollinators of apples and other fruit trees. They lay their eggs in pre-existing cavities. Squash bees, pollinators of cucumbers, squash and pumpkins, are a good example of ground nesting bees and emerge as adults in the summer.
Cavity nesting habitat
Putting out bee boxes on your property for cavity nesters is a great way to help establish and grow populations of different bees such as blue orchard mason bees or leafcutter bees. We prefer to use disposable paper straws, 6-8 inch cardboard tubes, or hollow plant stems in our cavity nesting bee boxes. That way we can clean them out and replace them year to year to avoid the buildup of parasites and disease. Drilled blocks are more difficult to maintain. The straws are placed within wooden boxes or other handy holding devices (e.g. cut open plastic water bottles) that will keep them dry. These boxes are then attached on the south side of posts or buildings or trees. If the tube is accepted, a female mason bee will put a pollen ball in the end of the tube and lay her egg on it. With a little clay mud, she will seal up the egg and pollen ball in a small chamber. She will continue to place pollen balls and eggs in the tube, sealing off each chamber as she does. When she’s done, there will be 6 or so sealed chambers with pollen balls and eggs. Leafcutter bees line their nest holes with small cut pieces of leaves. We are delighted when we see the half-moon shaped holes cut out of our rose leaves. Please don’t reach for the pesticides if you see these holes on your rose leaves! These are your pollinators in action.
Different species of bees prefer different size holes. Cardboard straws are available from suppliers, but we also use hollow stems and sticks with pithy centers that we drill out with the appropriate drill bit. Generally, the tubes should be replaced annually to prevent the spread of pests and diseases.
Sometimes mason wasps or grass carrying wasps will use the holes designed for the bees. They bring in tree crickets (grass carrying wasps) or caterpillars (mason wasp), lay their eggs on them for their carnivorous larvae, then seal the hole with mud or grass. Although they’re not great pollinators, they’re beneficial in that they take many of our garden pests and use them for food for their larvae.
Leaving plant stems and having unmowed areas with elderberry, sumac, Joe Pye weed, and other hollow or pithy stems is another way to provide nesting habitat for these cavity nesting bees. The small carpenter bee (Ceratina) loves to dig tunnels in the pith of last year’s raspberry canes. We prune 6 inches above ground level to leave some vertical stems above ground. We also leave our prunings in piles that are accessible to these little pollinators. Celebrate the scruffy with Ceratina!
Ground nesting habitat
Many ground nesting bees, including squash bees and cellophane or plasterer bees, like open sandy soil to tunnel and build their nests for egg laying. They especially appreciate a south facing slope. Leaving these open spaces in the fields, gardens, or back yards is a great way to encourage these delightful and docile bees. Some will aggregate in favorable spots with hundreds of holes in a small area. For years, we have only seen a few plasterer or cellophane bees around in the spring on our farm. To encourage a larger population, we created sand box patches this past year and introduced bees caught at other sites. This is part of a new Northeast Sustainable Agricultural Research and Education (SARE) Program grant that looks at ways to establish ground nesting (Colletes) bees on farms.
Enhancing Floral Resources
When native bees emerge from overwintering, they need to feed and gather pollen for their soon-to-be-laid young. One of the earliest blooming shrubs are willows. These include purple osier willow (a favorite of basket makers), pussy willows, black willows and dozens of others. One of the first things we did on our farm when we bought it 25 years ago was to allow the willows, birch, box elder and other trees to grow up in the seasonal stream that runs through the back pasture. Traditionally, this pasture was hayed and mowed to the edges of the stream. The stream was considered a ditch and regularly cleaned out and straightened so as to remove water off the land as quickly as possible. We wanted to take advantage of the water by slowing it down to collect nutrients and to create biodiverse habits. Our stream is now a wooded stream corridor and provides a variety of willows and other early flowering woody plants for bees. It also provides habitat for birds, amphibians, beneficial insects, and other wildlife. We periodically coppice some of the trees and willows to make ramial wood chips that we use on our perennial plantings.
Service berry blossoms are another early flower in northern Vermont and are common around the edges of woodlands. Also called Juneberries, they bear edible fruit in June which is a favorite of the birds. Varieties called Saskatoons, developed in Canada, have larger berries and are used for crop production. These make a great addition to edible landscaping projects and also serve as floral resources for pollinators. Haskaps, also called honey berries, are another early bloomer, flowering in early May on the farm. The bumblebee queens love the yellow flowers and we love the bluish/purple berries in June. We and the birds, that is.
We occasionally see bee visitors on the early daffodils around the house and Siberian Squill under the apple trees. Providing nectar and pollen resources during this early spring “shoulder” period can help not only the native bees but your or your neighbor’s honeybees as well.
Mid May through early June is when most of our fruit trees and berry bushes are in bloom. Many native trees and shrubs are also blooming. Although we keep honeybees, it is the native bees that we see most active on our fruit crops. Many flowers require something called buzz pollination, where the bee vibrates the flower at a certain frequency which encourages the pollen to release. Blueberry flowers are a good example. Also, the shape of the blueberry flower has evolved to suit native pollinators like bumblebees with their longer tongues. That’s why enhancing the bumblebee population around your blueberry patch can help your blueberry production. Because bumblebees need season-long floral resources, it’s important to have food available during July, August and September, after the blueberry flowering period is over, if you want bumblebees around in May.
We turned our 14-acre back pasture and meadow into a pollinator sanctuary for that very reason. The first thing we did was stop mowing areas or we timed our mowing for once a year at the end of the season. We also reduced our animal population so we had stopped grazing as well. If we mow, it will be in October, after the Monarchs (the few that we might have) have pupated and begun their migration back to Mexico. This is also after the goldenrod and asters are done providing late season nectar and pollen for pollinators.
When we stopped grazing the back pasture, we also started planting. The first year we planted a small standard heirloom apple orchard (about 50 trees) with a variety of “guild” plants including nitrogen fixing alders, bayberry, and Siberian pea shrub, along with other fruit plants like currants, wild plums and rowans between the trees. Every year we add more trees and plants. We’ve planted pear trees, basswood, honey locust, and black locust trees in other plots as well. The nice thing about the basswood and locust trees is that they bloom in June, later than the pears and apples thus providing additional pollen and nectar for bees without competing for their attention.
Between the rows of apples and pears, we allow the milkweed to grow. Their sweet pink flowers are loaded with native and honeybees in June and July. They’re also host to a variety of beetles, bugs, and an occasional Monarch larva. Orb weaver spiders with their bright yellow patterning dangle on their complex webs between the milkweed plants. It is a beautiful sight!
Last year, we harvested milkweed pods and sold them to a milkweed coop in Canada. Milkweed floss is buoyant and water resistant. It was used during WWII for life jackets by the Allies because the place where the Kapoc trees grew (the traditional life jacket material) was occupied by the Japanese. This was before the advent of synthetic fibers. But the natural floss fibers are making a comeback in Canadian coast guard life vests and fiber fill for comforters and jackets.
We continue to plant hundreds of shrubs and perennial flowers favored by bees like button bush, dogwoods, highbush cranberry, liatris, ironweed, swamp milkweed and more. It’s important to note that bees prefer white, pink, yellow and blue flowers, so we tend to focus on those colors when planting perennials and annuals. We do have some red bee balm which brings in hummingbirds and butterflies. Because many bees tend to practice floral constancy and preference while foraging, it’s better to plant patches of flowers rather than one here or there.
In the wetter areas of our pollinator sanctuary, reed canary grass had taken over. We planted willows, elderberry, wetland roses, nanny berry, and other native shrubs and used a woven landscape fabric for weed control. The fabric can be pulled up in a few years after the plants are established and can shade out the grasses. We reuse the fabric for other plantings.
Several years ago we conducted a study funded by SARE to look at using cover cropping as a way to enhance floral resources. A short summary video about this research can be found at www.thefarmbetween.com/resources/. Although we have moved to mostly a no till perennial polyculture farm, as vegetable farmers we knew the importance of cover cropping for enhancing the soil, preventing erosion, competing with weeds and other benefits. Our study looked at adding another important cover crop function, that of nectar and pollen resources for pollinators. We conducted replicated trials of buckwheat, phacelia and a perennial conservation mix. Cover cropping with flowering species like buckwheat, vetch, and clover, is a great way to enhance these bee resources and do your soil a favor.
The perennial conservation mix did not fare well in the short term, and it took a couple of years to get established, but in the long term, it has turned into a wonderful bee resource — especially the early season lupine, and the late season, perennial Maximillian sunflowers. While our annual plots from that research have long since been converted to perennial plantings, our perennial conservation mix plots have remained as permanent bee resources.
Besides enhancing floral resources for the native bees, planting a diversity of native plants, shrubs, and trees also provides places where beneficial insects, spiders, birds and other insectivores can live. This in turn builds a natural pest management program for the farm and garden. For some people these wild and unmanaged areas in and around the farm and garden, as well as only late season mowing in certain areas of the property, look unkempt. We think it’s time to rethink pretty. Knowing that these beautifully scruffy areas are ecologically diverse and beneficial to bees, birds, and others will hopefully change some attitudes. Well-manicured green lawns are actually biological deserts and if certain lawn products are used, they could even be toxic lawns. We need to create and celebrate biodiversity throughout our living and working landscapes.
In summary, there are many things that landowners can do to enhance pollinators and pollination services on their property. Creating a biodiverse landscape with season-long floral resources and nesting habitat for native bees is a great first step that will bring immediate results. By observing the miracle of the plant and pollinator interactions, we feel more connected with our natural world. Besides, we all want bountiful farms and gardens including our partners, the native bees.
John and Nancy Hayden own and operate The Farm Between in Jeffersonville, VT, an organic fruit farm and fruit nursery. They specialize in cold-hardy fruit trees, uncommon berries, and pollinator conservation plants. John is also a pollinator habitat and fruit pollination consultant. For more information, visit www.thefarmbetween.com.