Safe nest sites and overwintering sites are as essential to the survival of pollinators as sources of nectar, pollen, and host plants for caterpillars. The suggestions listed below are culled from a variety of sources. We have done our best to seek out reliable sources and offer a condensed summary of best practices. We have listed many sources for more information in the resources section of the website which we hope will provide further guidance and inspiration. For those beginning to create habitat for pollinators, don’t be overwhelmed by the amount of information; choose one suggestion and start with one change that feels satisfying to you
The majority of bees, about 70%, make their nests in the ground.
Things you can do to support ground-nesters:
Protect existing nests. Survey your landscape for active nests in the spring. Tunnel entrances to bee nests often resemble ant mounds with excavated soil piled around a small entrance hole. Watch for bees entering and leaving through the opening. If you locate a nest, protect it from mowing, cultivation, or trampling.
Leave an area of undisturbed bare ground so bees can make new nests and be safe from disruption. Different bee species have different preferences for ideal nesting sites. Below are some preferred conditions for nest sites of various species:
* Sunny areas on south-facing slopes
* Areas of bare soil among rough patches of clump-forming grasses that leave spaces between plants . Most lawn grasses are chosen for their habit of filling in all gaps. Native clump grasses grow with spaces beneath and between plants that offer great nest sites and protection for nesting pollinators.
* Wild patches of grassy or weedy areas where rodents can make protected nesting cavities. Many bumblebees will nest and overwinter in abandoned rodent nests.
* Any area of bare soil, especially on banks and slopes
* Unpaved driveways and small patches of compacted dirt.
* Lightly-compacted earthen pathways in gardens.
30% of bees nest in cavities including Mason Bees, prolific orchard pollinators.
Things you can do to support cavity nesters:
Leave standing dead trees in place where they do not create safety hazards. Some bees use tunnels in decaying tree trunks and limbs that were made by boring beetles or woodpeckers.
Leave fallen logs or other woody debris in place or add it to your garden by design. If you don’t want to rely on beetles for the tunnels, you can drill some deep holes in upright logs on the sunny side of the wood. Different sized holes will attract different bee species.
Do not cut back your perennial garden until spring. Bees will find their way into hollow stems through existing holes or wounds in the stems and lay their eggs in the hollow center, creating separate brood chambers for each egg. Many plants will serve including elderberry, sumac, raspberries and blackberries, New England aster, monarda species, several goldenrods, tall coreopsis, and cup plants. The standing plants will also provide cover for overwintering pollinators and beneficial insects as well as cover and forage for birds.
When you cut back your garden in the spring, cut long stems and lay them in an out of the way place until late-maturing species have a chance to emerge safely. I usually leave my debris until mid-summer before adding it to my compost.
During spring clean-up, leave some clumps of pithy stems cut to about 15”-18” for species such as small carpenter bees which create their own nest holes in these stems. A fuzz of debris at the top of one of these stems is a sign that it is being excavated for a nest.
Suggestions for enhancing and building nest sites for ground-nesting bees and cavity-nesting bees can be found on the Xerxes website at this link to their fact sheet on Nests for Native Bees.
Provide and protect overwintering areas for bees and other pollinators.
Some bees overwinter as adults by returning to the same nest-sites they emerged from in the spring. The queens of some bumble bee species over-winter this way, and protecting them means protecting the source of next year’s bees.
The larvae of many bee species will overwinter in their original brood chambers within a nest. They will emerge as adults in the spring or summer.
Leaf litter provides winter protection for adult bees of some species. It is also an important overwintering habitat for the larvae or pupae of many moth species. Some butterfly species overwinter as caterpillars or pupae in the leaf litter beneath or near their host plants.