Solitary bee hotel: which species will actually move in

At a glance: who actually nests in a tunnel block

• Red mason bee (Osmia bicornis) — March to June, 7–9mm, seals cells with mud.
• Blue mason bee (Osmia caerulescens) — April to July, around 6–7mm, less common but a similar mud-nester.
• Leafcutter bees (Megachile species) — June to August, 5–7mm, seal cells with cut leaf discs.
• Masked and yellow-faced bees (Hylaeus species) — summer, 2–4mm, easy to miss entirely.
• Wool carder bee (Anthidium manicatum) — June to August, around 6–7mm, lines cells with plant down.
• Species you will not get: mining bees, furrow bees and bumblebees — all ground- or cavity-nesters unrelated to tunnel width.

Red mason bees: the one nearly every garden gets first

If a UK garden hotel gets any tenant, it is usually Osmia bicornis. Males emerge first in March, patrol the entrances without nesting, and die within a couple of weeks. Females arrive a little later, mate, then spend six to eight weeks provisioning tunnels: a pollen loaf, an egg, a mud partition, repeated down the tube, daughters at the back and sons near the front. They need 7–9mm tunnels and, critically, a source of workable wet mud within easy flying distance — see our dedicated mason bee guide for exactly what that means in practice.

Leafcutter bees: the summer shift

By the time mason bees have finished for the year, leafcutters (Megachile species) take over the same tunnels in slightly narrower diameters. You will know they have arrived because rose and lilac leaves nearby develop neat semicircular notches — cut, rolled, and carried back to line and cap the cells. It is cosmetic damage only and a sign the hotel is working, not a pest problem.

The overlooked species: masked bees and wool carders

Most bee hotels sold in garden centres are drilled from 6mm upward, which quietly excludes an entire tier of smaller bees. Hylaeus species — small, wasp-like, and often mistaken for flies — need tunnels as narrow as 2–3mm. The wool carder bee, distinctive for scraping fluff from lamb's ear leaves to line its nest, sits in the middle of the range at 6–7mm. A hotel that stops at 8mm has already ruled several of these species out before a single bee has arrived.

Tunnel diameter by species

Common mistakes that keep a hotel empty

• One diameter only. A hotel drilled entirely at 6mm or entirely at 8mm rules out most of the species above.
• No mud source. Mason bees are the most likely tenant, and without wet soil nearby they simply move on.
• Wrong season for hanging. Put it up after March and you miss the mason bee emergence for that year entirely — see where and when to hang it.
• Expecting ground-nesters. The majority of solitary bee species nest in soil, not tunnels; a hotel was never going to house them.

What to look for when buying one

Buy for the species you actually have a chance of hosting: a spread from roughly 2mm to 10mm, not a single bore size repeated down every row. Depth matters as much as width — anything shallower than about 10cm produces mostly male offspring, since females lay daughters at the sheltered back of the tunnel. Every tunnel should be sealed at the rear, sanded smooth, and sheltered under a roof that actually overhangs the entrances, not a flat lid that lets rain run straight down the face.

The Wild Bee Hotel is built to that specification: tiers running the full 2mm to 10mm range, hand-sanded inside and at the rim, 10–15cm deep, set into 19mm untreated Western red cedar with a solid rear panel and a hand-formed copper roof that overhangs the entrances on every side. £39.99 for one, with options for two, three or four, free worldwide shipping and a 30-day money-back guarantee — for the hotel, not for any bees already settled in it.