Gardening for Native Bees

spread pesticide use, and climate change all have an impact, but gardeners can help. AppreciAting Diversity American bee species “come in a jewel box gardening for of different colors—from metallic green to bottle blue, gold, brown, and glossy black,” says scott Hoffman black, the executive director of the Xerces society, an organiza- tion dedicated to invertebrate conservation. sizes vary from the enormous one-inch val- Native Bees ley carpenter bee (Xylocopa varipuncta) to one of the world’s smallest bees, Perdita minima, which is under two millimeters North America’s native bees long. Throw in different shapes, hair types, tongue lengths, and other characteristics, are under threat from habitat and their diversity is staggering. When it comes to nesting, about loss, pesticides, and climate 90 percent of these species are solitary, change. Here’s what gardeners can do to help. BY JESSIE KEITH Left: Fall-blooming plants such as this aster (Symphyotrichum sp.) provide nectar to many species of native bees as they prepare to hibernate over the winter. Above: Specialized hairs on the underside of this female leafcutter bee’s (Megachile sp.) abdomen hold the pollen she collects for feeding her young. oney bees (Apis mellifera) (Osmia lignaria) are far more effective while the rest are social and hive-form- may garner more of the lime- pollinators of cherry orchards, resulting ing. nests may be underground or above Hlight, but north America is al- in over twice the fruit yields of honey bee ground in cavities; depending on the so home to approximately 4,000 known pollinated orchards. This is not surpris- species, nests may be constructed from native bee species that are just as agricul- ing given that many native bees are often mud (mason and plasterer bees), plants turally, horticulturally, and ecologically more tolerant of cool or moist conditions (leafcutter bees), earth (mining bees), or Bees like this eastern carpenter bee (Xylocopa important. While they don’t form large, and have longer foraging times—giving excavated wood (carpenter bees). sol- virginica), here taking a shortcut to nectar by slicing honey-making colonies like their better them the pollination edge. itary bees tend to produce few young through the side of a hosta flower, are among known but non-native counterparts, However, like honey bees, native bee (often one to 10) in underground nests, hundreds of bee species native to North America. these indigenous bees are among the populations have been declining over the while some bumble bees and sweat bees most essential pollinators in our natural last several years. This decline “speaks to- nest in aboveground crevices and pro- areas, farm fields, and gardens. wards land use and the lack of diversity of duce small colonies. some north American species even ap- our vegetation,” says Deborah Delaney, There is a direct correlation between bee pear to do a better job of pollinating crops bee specialist and assistant professor of en- size and flight distances, larger species like than honey bees. For example, researchers tomology at the University of Delaware in bumble bees can fly up to a mile or more JESSIE KEITH JESSIE LEFT: VIVEKA NEVELN. RIGHT: BILL JOHNSON. have found that blue orchard mason bees newark. Factors such as habitat loss, wide- when foraging, while medium to small bees 34 the American Gardener November / December 2014 35 may only forage a couple hundred feet from their nests. Most native bees are polylectic, BASIC BEE CHARACTERISTICS which means they pollinate a wide variety Bees are closely related to wasps, so share several features pollen. These structures are either corbiculae (“pollen baskets” of plant species. others may be oligolectic such as large compound eyes on the sides of their heads consisting of a smooth concave area with fringes of curved long (pollinating a few, closely-related plant and two pairs of wings. hairs) that hold pollen, species) or specialized even further to be However, a number of or scopae (patches of monolectic (pollinating one plant species). characteristics distin- stiff hairs) to which pol- guish the two insects. len can adhere. nurturing nAtives Physically, the most Some wasps—such With these basic facts in mind, there are obvious difference be- as yellow jackets or several things gardeners can do to sup- tween the two is that bald-faced hornets— port native bees. “If every gardener tried to bees tend to be much can be aggressive when create a haven for bees, it would increase hairier than wasps. defending themselves, habitat exponentially,” notes black. Pro- These soft hairs are but there is little to tecting and providing nesting areas and feathered or branched, fear from native bees food sources are key. equally important whereas any wasp hairs in general. “Most soli- are straight. While most tary bees don’t or can’t wasps are carnivorous, sting,” says Scott Hoff- all bees are vegetarians. man Black, executive Wasps do not collect director of the Xerces pollen, and only female Hairiness is one conspicuous characteristic that differentiates bees like this mining Society, a nonprofit or- bees collect and trans- bee (Andrena dunningi), left, from wasp cousins like this paper wasp (Polistes sp.) ganization dedicated to port pollen to nests to invertebrate conserva- feed their young. For this purpose, they often have specific tion. “Bumble bees can sting but they rarely do,” he adds. structures on their hind legs or abdomen adapted for carrying Male bees do not have stingers at all. —J.K. suggests that gardeners aim for at least 20 different plant species overall to bring the bees, based on bee population sampling he has conducted around California. no matter the season, Frankie found the rich- est diversity of bee species in berkeley and santa Cruz. by contrast, he found “little in the way of bees in san Diego,” he says. He attributes the difference to the regional plant palettes—landscapes featuring a few plant species with limited wildlife value A spacious, artificial hive, right, may appeal correlated with very low bee diversity and to honey bees, but a modest piece of wood numbers in general. “The more bee-plant drilled with numerous holes like the one biodiversity you have, the more diverse the above provides many native solitary bees bees you will attract,” he notes. with ideal nesting sites. plAnts thAt AttrAct bees is safeguarding bees from pesticides. All compost or leaf mold instead. If this is not ing bees; bamboo, teasel, and reeds all work As a general guideline for deciding which broad-spectrum pesticides can kill bees, feasible for you, try doing this in just a small well for making these nest bundles. plants to include in your garden to at- but research shows that neonicotinoid area of your yard that you leave “wild.” Most essential to healthy bee habitat is tract native bees, it’s helpful to keep in pesticides used in agriculture and horti- For above-ground nesters, you can cre- a variety of plants to ensure a steady sup- mind that flowering plants that depend culture—such as clothianidin, thiame- ate artificial nest sites. For example, layers ply of nectar and pollen. nectar is a bee’s on bee pollinators to reproduce have thoxam, and imidacloprid—are the most of clay-mud blocks may encourage certain main energy source. nutritious pollen, rich Sweat bees, like the one here visiting a black-eyed Susan, are efficient pollinators. specific suites of floral traits adapted to harmful. because neonicotinoids main- southwestern bee species adapted to arid in protein, nutrients, and oils, is primarily attract them. These traits include “land- tain residues in pollen, they can poison conditions to nest in the cool cracks between used by bees to feed developing larvae. sol- produce young at different times, so ideally three for fall,” says black, “so there is a buffet ing pads” for bees to rest upon while pollinators long after application. blocks. “nest blocks,” either purchased or itary females typically roll the pollen into your planting scheme should ensure that of flowers throughout the growing season.” collecting and feeding, sweet fragrance, To encourage native ground-dwelling homemade from wooden blocks drilled nectar-infused balls of “bee bread” and lay something is in bloom during all the sea- Gordon Frankie, professor of urban and sugary nectar. The flowers tend to be bees to nest, avoid disturbing areas of bare, with holes, appeal to tunnel-nesting species. a single egg on each ball. The pollen is all sons, even winter. entomology at the University of Califor- shades of yellow, blue, or white with spe- friable earth around plants as much as possi- bundles of hollow stems cut and positioned the food larvae need to develop and ma- “I recommend planting three good bee nia, berkeley and director of the Urban cial markings that guide bees to nectar. ble, and avoid applying bark mulch. Choose cross-wise are also attractive to tunnel-nest- ture into adult bees. Different bee species LEFT: BILL JOHNSON.RIGHT: JUDYWHITE, GARDENPHOTOS.COM. TOP LEFT: BILL JOHNSON.RIGHT: TOP COURTESY OF DAVID CAPPAERT, MICHIGAN STATE UNIVERSITY,BUGWOOD.ORG. BOTTOM: COURTESY OF TIM STANLEY, NATIVEBEEOLOGY. plants for spring, three for summer, and bee Lab, concurs with this strategy. He Many are tubular with bilateral symme- 36 the American Gardener November / December 2014 37 try, like salvia and snapdragon flowers, or in heads, as with daisies and sunflowers. NATIVE PLANTS PROVIDE A SMORGASBORD FOR BEES because native bee and plant species The following native plants attract a wide variety of native bee species and other pollinators throughout different seasons. They evolved together, growing native flow- are also relatively easy to grow and adaptable across several regions. For many of the genera listed below, there are several ering plants is a good way to attract local other species that are good pollinator plants, too.

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