Lupinus perennis production field

Incipient Spring and Pollinator Palaces

Mar 13, 2015

This week at the Nursery was absolutely beautiful. It finally felt as if winter was exhaling a bit. We had chilly nights, foggy mornings, which often gave way to beautiful sun and temperatures in the 50s. You can feel that spring is on the verge of cracking through. Before we know it the buds on the trees will be opening and there will be greenery. We can even look forward to some early blooms in April, like Caltha palustris (Marsh Marigold), Phlox divaricata (Woodland Phlox) Geum triflorum (Priairie Smoke), Aquilegia canadensis (Wild Columbine), and Lupinus perennis (Wild Lupine).

Native bumble bee on a flower of Lupinus perennis

Working toward the production of native plants, pollinators are a huge concern for us, particularly native pollinators. While European honey bees can certainly be effective pollinators for some native plant species, others have coevolved with native insects to the point that native pollinators and only native pollinators can get the job done. With estimates of the value of pollination and other ecosystem services provided by native insects reaching into the tens of billions, it is certainly worth our while as native horticulturists to protect and promote native pollinators.

We certainly do this through all of the natives we grow and sell throughout the Midwest and the country (over 5 million plugs, over 1 million bareroot plants, and over 16,000 acres of native seed since 2006). But we are also trying to provide habitat and shelter for our native pollinators by distributing native bee hives throughout our property. This week, we’ve been constructing some hives and bee blocks for native bumblebees (Bombus spp.), and orchard mason bees (Osmia lignaria).

Each species has specific needs, and therefore a distinct shelter type. Fortunately, these shelters are relatively easy to build, and can be incorporated aesthetically into any garden or native planting.

Bumblebees, of which there are several species native to North America, are social bees, and fairly flexible in there nesting needs. Bumblebees might nest in cavities created by folded over grass, or piles of woody brush. This shelter is made by constructing a simple wooden box, approximately 7”x7”x7”, with a ¾” I.D. PVC pipe as an entrance.

Bumblebee nesting box made from lumber and a PVC pipe

All we need to do is nail a lid on top, drill some ventilation holes in the side, and place it in a cozy spot along one of our tree lines here at the Nursery.

Orchard mason bees, unlike bumblebees, are solitary tunnel-nesting bees. They cannot carve out into wood, but generally make their homes in natural holes, or those abandoned by other insects. This “bee block” is easily constructed by screwing together 2-3 foot lengths of untreated 2x8 lumber. Holes are drilled to a depth of 4-6” with diameters between 3/32 and 3/8”. Holes should be spaced at least ¾” apart. The seams between the laminated boards are sealed with silicone caulk, and the block has been mounted to a fence post. The blocks can also be attached to a tree or outbuilding, preferably a few feet off of the ground to prevent rainwater from splashing up onto the blocks. 

mason bee block made from untreated lumber

Although we already have several of these structures located around the nursery, we are constructing an additional six bumblebee boxes and six mason bee structures to supplement natural habitat. They will be placed on the periphery of our production plots, with close proximity to nectar and pollen sources. There are several other shelters that can be built for our local pollinators. This guide from the Xerces Society provides more detail on these and other shelters.

As helpful as building shelters for pollinators can be, habitat loss is widely regarded as the number one contributor to pollinator decline. To that end, we’re looking forward to another beautiful season of producing and spreading native plants around our region and beyond: Millions more native plants and plugs, and thousands of acres of native seed. Here’s to the coming spring!