It is a charming thought to provide bees with a hotel in your garden but what you don't know can actually end up harming them. Bee hotels are good in theory and when done correctly they can provide a vital and missing nesting habitat. So what do you need to be mindful of when you buy or build a bee hotel?
Get to Know Your Guests
The bees that nest in bee hotels are different than honey bees or bumblebees. Your bee hotel will attract solitary bees that don’t live in colonies, they don’t build hives, they don’t make honey or wax, and they don’t form attack swarms.
Many hole-nesting bees are too small to chew their own holes in solid wood. Instead, they save time and energy by nesting in pre-made holes like old grub tunnels.
Cautions
If you don't maintain a clean hotel then your guests will struggle with disease, pests and predators. To reduce and deter diseases and pests is easy, simply harvest cocoons and separate healthy cocoons from infected nesting chambers.
Because man-made nesting holes are usually much closer together than the nesting holes found in nature, common native bee diseases and pests can spread and overrun a bee hotel.
The three big problems that hole-nesting bees face are pollen mites (they eat the pollen and nectar loaf before the bee larva does)
chalkbrood (a fungal infection that converts a larva into a mass of fungal spores)
parasitic wasps (gnat-sized wasps that lay eggs inside of healthy larvae). As you harvest cocoons, you can learn how to identify infected chambers and keep healthy cocoons safe. Also ants, certain beetles and birds.
Pre-made, store hotels are often badly designed and don't offer a suitable spaces. The warning sign of such designs is the unnecessary use of pine cones, glued snail shells, wood shavings and clear plastic tubes. Many off-shelf insect hotels or build-your-own websites do not come with clear guide on maintenance.
Tips
Freshly purchased pressure-treated wood should be avoided as the chemicals inside will deter the bees
The frame must be enclosed at the back
Must have a roof overhang
The wooden frame maybe left unfinished, coated with an exterior wood sealant to protect it from the elements, or painted. Just know that the smell of paint and sealant is likely to deter bees for at least a few weeks until it wears off.
It should be roughly chest high and facing south. It must stay warm.
Tube depth should be 6" or more
Inspect at the end of summer to remove and clean dead cells to prevent mold and mites. Some experts recommend bringing occupied insect hotel into cool dry area such as garden shed during winter
You should not have large wide holes
Notes from The HoneyBee Conservatory
1. Protect developing larvae. Plan your bee hotels ahead of time so that you can remove nesting materials as they are filled and store the filled nesting holes in a warm location. You want to keep nesting materials in locations that have similar temperatures as the outdoors, like a garden shed or unheated garage. Removing and protecting filled nesting holes in a fine mesh bag keeps the small parasitic wasps from being able to attack larvae. To protect a drilled block of wood, place liner inserts or rolled paper inserts (pinch the back end closed) into each drilled hole and remove and replace these as they are filled.
Keep an eye on the filled nesting materials. Parasitic wasps may have already attacked and they are able to develop into adults very quickly, you don’t want them to harm more larvae. Also watch to see if your bees are the type that develop in the same season they were laid and are ready to emerge.
2. Provide nesting holes in the proper size range, made of the right materials. Avoid bamboo and plastic straws, as these do not let the moist pollen loaf breathe. Many bamboo shoots are much too large for any North American bee to use. Nesting holes should be between 4-10 mm in size and should be about 6” long. Nesting holes that are too shallow will skew the sex range of next generation’s bees. Natural, locally available nesting materials are best. You can also use cardboard tubes and lake reeds in the right size range and they are easy to open for cocoon harvest.
3. Protect nesting materials from wind, rain, and birds. Build a protective outer structure that has a 2-3” overhang. If birds are attacking the nesting holes, use 1” wide wire cloth and bubble around the bee hotel. Do not install wire cloth flush against the nesting holes because this will obstruct the bees from entering. Bees need some landing space for approaching and taking off.
4. Avoid a hotel that is too large. While a bee hotel that is 4 feet wide and 6 feet tall looks great, draws a lot of attention and raises awareness to our bees, this size is much too ambitious and will become a burden to maintain. Provide bee hotels that matches what the area nearby the house can provide, for example, many flowering trees and bushes can provide more pollen than a meadow of flowers can. Also, think about the time that you can devote to cleaning and managing the bees that move in.
5. Location and a word about solitary predatory wasps. Orient the bee hotel to face the morning sun, as hole-nesting bees are cold-blooded and need the sun’s warmth to get the energy needed to fly. We know that mason bees prefer some afternoon shade and have heard that too much shade could actually attract solitary hole-nesting wasps. Solitary wasps are predators of garden pests and they fill nesting holes with caterpillars, aphids, and even spiders. Hole-nesting wasps are great beneficial insects that are a good indicator that your garden is balanced and supports all insects. Solitary wasp larvae are also white but their shape and skin are different from a bee, they are longer with large bumps and they feel waxy.
You might want to provide two bee hotels in your yard with each bee hotel facing a different direction. One house can face east and another can face southeast. We are curious to learn if bee species have a preference for orientation of their nesting house. You might also want to place bee hotels in your yard and one in a wild location, like a meadow or forest. A natural habitat could be home to a different mix of local wild bees that you could then introduce to your yard.
6. Harvest cocoons. After protecting and storing filled nesting materials over the winter, open materials and harvest cocoons in the early spring. If you can, organize and separate cocoons based on appearance and when their nesting holes were capped. When you incubate in a mesh bag, you have more control for releasing the bees outside. Incubating inside of the fine mesh bag also helps you reduce the release of the gnat-sized parasitic wasps.