Planting more bee-friendly flowers is a major way we can support native pollinators like our solitary bees — the ones that don’t live in hives — but planning safe nesting sites can also help.
Some of the solitary bees we can provide nesting sites for most easily are different kinds of tunnel-nesting bees, like Mason bees and Leaf-cutter bees. You may have seen various versions of these hotels for sale at garden centers and online. Most include blocks of wood with holes drilled through or bundles of tubes such as straws or bamboo.
Bee hotels for our native, solitary bees can increase the number of pollinators in our small gardens, without taking a lot of space.
What you need to know to build a bee hotel
I am not going to give specific “how to” instructions for putting together a good bee hotel, because University of Nebraska has done an excellent job in their publication, linked here: Creating a solitary bee hotel. It includes photos showing a diversity of bee hotels.
However, these are University of Nebraska’s basics:
- Build a frame for your blocks or tubes. The wood should be untreated. The frame should be about 6-inches deep.
- Fill the frame with blocks of untreated wood in which holes are drilled to create the tunnels.
- More simply, skip the frame and just drill holes in big-enough pieces of untreated wood.
- Different diameters of holes attract different kinds of bees.
- In general, tunnel diameters should range from 3/32″ to 1/2″. The Nebraska publication includes a chart that shows which bees use which sizes of tunnel diameters.
The Nebraska publication focuses on drilled blocks of wood. Xerxes Society’s publication Tunnel nests for native bees tells more about using bundles of hollow stems or straws to create nests for tunneling bees. In general, though:
- gather your hollow stems, all about 6-inches long
- bundle them together in a protective container
- inside the container, the stems/straws should be horizontal
If you do not have a ready source of bamboo or other hollow stems, consider these Milliard Mason Bee Nest Tubes, made of cardboard.
Cleanliness saves (bee) lives
Parasites, moulds, and diseases can build up inside a bee hotel if it is not well-maintained.
Blocks should be replaced after one or two seasons of use. Old blocks that may still have bees developing inside should be kept aside someplace cool and dry until the following spring, when they can be set out for the bees to emerge.
Hollow stems and straws should be replaced, also, after they have been used and vacated.
After a couple of years, if the bee hotel is still holding together well, in winter, remove the blocks and bundles of tubes, then sanitize the frame by soaking it for about five minutes in a strong bleach solution. After the frame has dried completely, refill it with fresh blocks or tubes.
Smaller bee hotels may be better than larger ones
The Xerxes Society publication includes this information about the benefit of creating several smaller nests and hanging them at intervals through your landscape:
This prevents the unnaturally high populations found at nest blocks with many holes, and mimics natural conditions of limited, spatially separated nest sites. These smaller nests also decompose more rapidly, and can be allowed to simply deteriorate naturally, while new small nests are added to the landscape periodically.Xerxes Society. Tunnel nests for native bees.
Keep the hotel simple
Entomologist Jo-Lynn Teh-Weisenburger, in a blog post on the site The Entomologist Lounge, cites information that indicates the “increasing number of badly-designed artificial nesting sites contributed to higher loss of (solitary) bees by parasitism.”
The problem seems to one of trying to do too much with one hotel. She says, ” The warning sign of such designs is the unnecessary use of pine cones, glued snail shells, wood shavings and clear plastic tubes.”
Teh-Weisenburger suggests that better success may come when we focus on the kind of insect we want to attract and support. After creating a successful nest habitat for that insect, then we might consider adding structures — elsewhere in the yard — for other species.
Placement of the new nest
Bee hotels need to be set in place in early spring, before the first solitary bees emerge to start looking for flowers and for nesting sites. In my yard, that means placing the bee hotel in the yard by mid-March.
Publications agree that the bee hotel for tunnel-nesting bees should face south or southeast, to catch the morning sun, and it should be mostly in the sun all day. The hotel should be 3-5 feet above the ground, and any vegetation in front should be pruned away. It needs to be secure, so the hotel doesn’t sway in the wind.
Tunnels will stay drier if the hotel has a bit of a roof built onto it, that overhangs the front.
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