By Brian Barth
Many of these so-called "solitary bees," which include mason bees, leafcutter bees and carder bees, look more like flying ants than fuzzy yellow bees, but they're valuable pollinators just the same. The traditional hive boxes used to house honeybees do nothing to attract native bees to your garden, but these unsung heroes will happily take up residence in a "bee hotel," where each can have a private room of their own.
"Communal bees" would be a more apt name for native bees, as most like to live in close proximity to one another, just not in the highly social confines of a hive (some of us can surely relate). Instead, they look for narrow tubular spaces, such as the hollow center of a reed or a crevice in a rock wall, where they can safely lay eggs and incubate their young. It isn't easy for a tiny bee to find the perfect home, especially in the city, so if you create the ideal living space—an easy hour-long project, requiring little more than a few scraps of lumber, some screws, and an electric drill—they will come in droves.
Step One: Build a Frame
The exterior walls of a bee hotel can be made with almost any lumber scraps you happen to have lying around. Freshly purchased pressure-treated wood should be avoided, though, as the chemicals inside will deter the bees. Older, weathered pressure-treated lumber is fine.
You can build the hotel as big as you want, and in any shape you want, though a rectangle about the size of a typical birdhouse (roughly 8" x 12") is a common and easy to construct design. The only real requirement, in terms of dimensions, is that the frame be approximately 6 to 8 inches deep. 1" x 8" lumber (which is actually ¾" by 7 ¼" wide) is ideal.
The frame must be enclosed at the back—lightweight plywood cut to size is perfect for this part—and open in front. The roof must be sloped to shed rain and must extend at least 2 inches over the front. You can use wood again, or, if you'd like, tack on a piece of corrugated metal roofing for a cute, barn-like bee hotel.
The wooden frame may be left unfinished, coated with an exterior wood sealant to protect it from the elements, or jazzed up with colorful paint. Just know that the smell of paint and sealant is likely to deter bees for at least a few weeks until it wears off.
Step Two: Add "Rooms"
The hotel "rooms" are nothing more than holes drilled into blocks of wood. You can use random scraps of lumber or even small logs cut from tree branches. Whatever materials you use, they should all be cut to the same length, which is determined by the depth of the frame (a minimum of 6 inches).
Native bees vary greatly in size; the bigger the bee, the larger the diameter and greater depth they require for their nest hole. Drill holes ranging from 1/8" to ½" in diameter into the end of each block or log, spacing them about ½" to ¾" apart. Holes larger than ¼" should be 5" to 6" deep, while holes ¼" or smaller should be 3" to 5" deep. Make as many hole-filled blocks as will fit in the frame, and then smooth out the openings with sandpaper to remove any sharp splinters left by the drill.
You may also fill portions of the frame with small-diameter pieces of bamboo, hollow reeds, or plastic tubing cut to the same length as the wooden blocks.
Step Three: Mount the Hotel
Mount your bee hotel on a fence post, exterior wall, or any other vertical surface with a couple of screws through the rear wall. It should be roughly chest high and facing south if possible, so it warms up earlier in spring and stays warm later in fall, extending the egg-laying season for the resident bees. Stack the blocks, bamboo, and any other bee rooms you've created inside the frame with the hole openings facing out.
Female bees will construct individual chambers throughout each hole with mud, chewed up plant material, and other substances, depending on the species. A single egg is deposited in each chamber, along with a bit of pollen for the baby bees to eat after they hatch. Once a tube is filled, it will be sealed off at the opening to prevent moisture and predatory insects from entering.
The hatched bees remain inside the sealed tubes through the winter, emerging as adults in spring when warm weather returns. After all the sealed openings have been broken by the exiting bees, bee experts recommend removing the old "rooms" and building a new set each year as a precaution against transmitting diseases from one generation to the next.
Reposted with permission from our media associate Modern Farmer.