How to Build a Bee Hotel for Native Bees: Sizes, Placement, Care

How To Build Bee Hotels To Help Save Native Bees

A bee hotel is a shelter packed with narrow, dead-end tunnels where solitary bees such as mason bees and leafcutter bees can lay their eggs. You can build a good one in an afternoon from a block of untreated wood drilled with holes, or from a bundle of hollow plant stems, fixed under a small roof in a sunny, sheltered spot. The details that matter most are hole size, depth, placement and cleaning, because a badly made hotel can do more harm than good.

The large arched structure above, labelled "Hôtel à Abeilles" (French for bee hotel), shows the idea at its most ambitious: compartments of drilled logs, bricks and stems under a curved timber roof. Your own version can be far smaller and still be useful.

Why native bees need help

North America has roughly 4,000 native bee species, and Europe has around 2,000. Most people picture the honeybee, but the honeybee is a managed farm animal originally brought to the Americas from Europe. Wild bees do much of the pollination of wildflowers and many crops, and some are more effective than honeybees on particular plants. Blue orchard bees, for instance, are prized pollinators in fruit orchards.

Many wild bees are in trouble. Loss of flowering habitat, pesticides, disease and changing climate have all been linked to declines, and several species have been listed as endangered. A garden cannot fix that alone, but flowers plus safe nesting places give local bees a real boost.

Most bee species are solitary: there is no queen and no hive. Each female builds and provisions her own nest, often near others of her kind. That is the behaviour bee hotels are designed for.

Which bees will use a bee hotel

Here is the part many guides leave out. According to the Xerces Society, only about 30 percent of North America's native bees nest in tunnels such as hollow stems or beetle holes in dead wood. Most of the rest dig nests in bare ground. So a bee hotel helps a specific group, mainly mason bees (Osmia), leafcutter bees (Megachile) and some small resin and carpenter bees, plus solitary wasps that are useful garden predators.

That makes two other things just as important as the hotel itself:

Flowers close by. A female mason bee makes many trips to gather pollen for each egg, so a hotel far from flowers will stay empty.
Bare soil. Leave a sunny patch of undisturbed, unmulched ground for ground-nesting bees.

A compact house like this one, mounted on a wall under a pitched roof, suits most gardens. Bamboo tubes and drilled wood give a range of hole sizes, and the roof keeps rain off the openings.

How to build one: sizes and materials

Drilled wood blocks

Use untreated, preservative-free timber; a 4x4 post works for small holes and a 4x6 for larger ones. Drill across the grain with a sharp bit so the inside of each tunnel is smooth, because rough splinters tear bees' wings.

Diameter: between about 2.5 mm and 10 mm (3/32 to 3/8 inch). Keep to one size per block so you can manage them easily.
Depth: roughly 7.5 to 13 cm (3 to 5 inches) for holes up to 6 mm, and 13 to 15 cm (5 to 6 inches) for wider ones. Deeper tunnels allow more female eggs, which are laid at the back.
Closed back: if a hole goes right through, add a backing board.
Spacing: about 2 cm (3/4 inch) between hole centres.

Hollow stems

Bamboo, reeds and similar stems work well. Cut each stem just below a node so the node forms a natural back wall, bundle them tightly with the closed ends together, and lay them horizontally in a box or tin. Paper or cardboard tubes sold for mason bees are another option and are easy to replace.

Roof and frame

Any rigid frame works: an old wooden wine crate, a birdhouse with its front removed, or a simple box. A small overhanging roof keeps rain out. Upcycled materials, such as a bent licence plate for a roof, are fine as long as nothing is coated with chemicals near the nesting holes.

Creative designs, from jars to cinder blocks

Big "bug hotels" like this one mix bricks with drilled holes, stacked logs, bamboo, bark and pine cones. They look wonderful and give shelter to many insects, from beetles to ladybirds, but for bees the useful parts are the drilled wood, bricks with narrow holes and the stems. Loose pine cones and straw mostly attract other creatures.

Popular home designs include:

Cinder blocks. Slide bundles of bamboo or drilled logs into the hollow cores. The concrete is sturdy and weatherproof, and it can be painted on the outside.
Mason jars or tins. Pack with cut stems or paper tubes and lay on their side or hang from a branch or shed wall. A jar sheltered from direct afternoon sun avoids overheating.
Wine boxes and pallets. Fill with drilled blocks and stems arranged in patterns for a decorative wall piece.
Clay pots. Upside-down pots stuffed with straw are sometimes used by bumblebees or other insects, though cavity-nesting bees prefer tubes.

Whatever the design, the tunnels themselves should meet the size and depth guidelines above. Smaller hotels with a few dozen holes are healthier than one huge structure.

Where to put your bee hotel

Morning sun. Face the entrances east or south-east so bees warm up early. In very hot climates, shade from strong afternoon sun, which can kill developing young.
Solid support. Fix the hotel firmly to a wall or shed rather than a swaying tree branch or fence post.
Height. At least a metre or so (a few feet) off the ground, out of reach of splashing rain and mice.
Near food. Within easy reach of flowering plants that bloom from early spring through summer.

Once tenants move in, you will see entrances sealed with mud (mason bees) or neatly cut leaf pieces (leafcutter bees). That is the sign that eggs and pollen loaves are inside.

Keeping the hotel healthy

A hotel concentrates many nests in one place, which also concentrates parasites and disease. The Penn State Center for Pollinator Research lists the main threats: chalkbrood fungus, pollen mites, parasitic wasps, cuckoo bees and beetles that steal food, and mice and birds that eat larvae. Research summarised on Wikipedia adds a further caution: some studies found hotels used heavily by introduced bee species, and a 2014 German survey judged only 3 of 40 nesting aids suitable.

Good habits make a big difference:

Clean or replace nesting material every other year, only after the bees have left.
Use an emergence box. Move used tubes or blocks into a dark box with a single exit hole, set it next to fresh material, and let adult bees fly out towards the light and nest in the clean tunnels.
Scrub reusable wooden blocks with a dilute bleach solution and let them dry fully before reuse.
Replace bamboo every couple of years, since it cannot be cleaned inside.
Fit fine mesh a short distance in front of the holes if birds are raiding the nests.

Common myths about bee hotels

"Any bee hotel helps." Not quite. Hotels with holes that are too shallow, open at both ends, rough inside or never cleaned can become traps for parasites. Quality matters more than size.

"Bee hotels save honeybees." Honeybees live in colonies in hives and never use bee hotels. The beneficiaries are solitary species.

"Solitary bees will sting my family." Mason and leafcutter bees are gentle and rarely sting, which makes a bee hotel a good project for children who want to watch nature up close.

Sources: Original article by Ariana Marisol for Real Farmacy, via Why Don't You Try This. Guidance: Xerces Society, Tunnel Nests for Native Bees; Penn State Center for Pollinator Research, Managing Your Bee Hotel; Wikipedia, Insect hotel.

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