Harvest season is here, so now is the time to save reeds and stems for bees to use next spring. Since I started saving various stems a few years ago, I discovered that cavity-nesting bees really like all-natural materials, and they fill cut stems quickly and uniformly.
Plants vary from place to place
The type of stems you have will depend on where you live, but I’ve had good success with lovage, teasel, drumstick allium, joe-pye weed, elderberry, and blackberry. I cut them in six-inch lengths and let them dry in the sun for a week or more. Some people like to cut just above a node in order to get a natural back end. I prefer to cut them without nodes so they fit in a can easier, but either way will work. If they don’t have a closed-off back end, the bees will build one by themselves.
The length, too, can be variable. But remember that most cavity-nesting bees lay male eggs in the last three or four positions within a tube, so if the tube is too short, you end up with mostly male bees. The females will only go so far into a tube before they build a back wall, so it’s hard to make the tubes too long. With that in mind, err on the side of too long instead of too short when you design your bee housing.
More variety attracts more species
Also, if you want to attract a range of species, be sure to use some hollow tubes and some pithy tubes. The ones shown below are all hollow (lovage and drumstick allium) but others like blackberry and elderberry are filled with soft pith. Certain bee species, such as the small carpenter bees in genus Ceratina, will only build in a tube that contains pith. This is because they chew the pith into a paste and use it for partitions.
Mason bees and leafcutters usually opt for the hollow kind of tube, so a variety of types will attract a larger selection of bees. The inside diameter can start pretty small (as for Ceratina and small Osmia) and can range upward to about 1/2-inch. I usually have a few very small, such as 1/16-inch, and a few very large, such as 9/16-inch, but most are around 1/4- to 5/16-inch. If you have too many tubes with large diameters stuck in a container, you will find bees using the interstitial space for nesting instead of the tubes. To prevent that, fill those spaces with smaller tubes to take up the slack.
I like to use a screened inner cover (shown below) for drying stems because you get good airflow on all sides, which makes the drying quick and uniform. If you don’t have something screened on the bottom, just roll the the stems when you think about it. After they are dry, stack them in a cardboard box until spring. Be sure to keep them in a dry place so they don’t get moldy.
I’m sure everyone has a plant that works well for pollinators in his or her area. How about you? What species make good housing where you live for both pith and no-pith bees?
Honey Bee Suite