I had great success last season with cavity-nesting bees using the hollow plant stems I collected and placed in various parts of yard. I am reminded as I wait for spring that many of the plant stems sticking up through the snow may already be filled with broods of larvae ready to emerge this spring. Another reason to not clean-up your garden in the fall because the leaves, branches, hollow stems, decaying wood and debris provide important overwintering sites for wildlife.
Native bees are abundant in urban and suburban landscapes and approximately 30% nest in cavities. Cavities include plant stems – some bees chew the pithy wood from the center of stems, others use preexisting holes in wood, most often in standing dead trees. Common cavity nesting bees are small carpenter bees (Ceratina spp.), mason bees (Osmia spp.), leafcutter bees (Megachile spp.) and yellow-faced bees (Hylaeus spp.).
There are many native perennial plants with hollow stems that can be collected and bundled to create nesting boxes. Bee boards are often constructed for mason bees by drilling long dead end holes in untreated wood boards, usually in 4″ or 6″ square boards. These boards require cleaning every two years with a bleach solution to eradicate any pathogens or disease-causing organisms. I have found hollow plant stems much easier to maintain because they can be easily removed and replaced every two years, and they are also abundant in my yard. Lay the old stems on the ground if empty and keep the others in a safe place until the larvae have emerged.
I purchase untreated 1×8″ or 1×10″ boards from my local lumber store where they sell remnant pieces for less than $2. Create an open-ended box, rectangular or square and hang in a sunny location on a fence. Put a back on the box if you plan to hang it where there is access to the back so woodpeckers don’t disturb the stems. The box should be at least 6″ deep; cut hollow stems to the length of the box and fill full.
Hollow-stemmed native perennials include cup plant (Silphium perfoliatum), joe pye weeds (Eupatorium spp.), pale Indian plantain (Arnoglossum atriplicifolium) and larger sunflowers (Helianthus spp.). While cutting down your perennial stems this spring, take a look at the plants in your landscape to determine which ones you could use for bee nests.
For shrub species, small carpenter bees like stems with pithy centers that they chew out to create a cavity. Elderberries, Sambucus spp. are ideal stems to collect. In the midwest, both the red elderberry, Sambucus racemosa and the Canada elderberry, Sambucus canadensis are abundant.
Grass-carrying wasps, Isodontia spp. also use hollow stems as nesting sites. These wasps are solitary and do not sting. Females fill the stems with prey (crickets and katydids), lay their eggs then seal the cavity with pieces of grass.
There are many creative examples of solitary bee nests, some people build beautiful ‘bee hotels’ with multiple layers of stacked stems, wood and other crevices. What natives in your area have hollow stems that can be used for bee nests?
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