What size holes should a bee hotel have — and how deep?
Diameter chart
| Tunnel width | Who uses it |
|---|---|
| 2–4mm | Masked and yellow-faced bees, small solitary wasps — nearly always left out |
| 5mm | Small leafcutters and smaller mason species |
| 6–7mm | Leafcutter bees (Megachile) |
| 8mm | Red mason bee (Osmia bicornis) — the prize tenant in most gardens |
| 9–10mm | Larger mason bees and some solitary wasps |
Anything much above 10mm tends to attract wasps rather than bees. The practical answer is not one size but a spread: offer roughly 2mm to 10mm and let whichever species are flying nearby choose for themselves.
How deep should the holes be?
Aim for 10–15cm. Depth matters more than most people expect: a female lays female eggs at the back of the tunnel and male eggs nearer the entrance, so a shallow tunnel of 4–5cm produces almost only males and does little for next year's population. Deeper tunnels also keep the brood further from temperature swings and from birds probing the entrance.
The details that go with the sizes
- Closed at the back. A through-hole is a corridor, not a nest, and it lets parasites in from behind.
- Smooth inside. Splinters on the tunnel wall shred wings over hundreds of entries. Run a fingertip in: if it catches, it is too rough.
- Clean entrance rims. Sawn bamboo nodes and torn drill exits both cut.
- Spaced out. Holes too close together weaken the wood between them and the walls crumble.
- Horizontal, or tilted very slightly down. Uphill tunnels collect water.
How the Wild Bee Hotel is drilled
Tiers of tunnels from 2mm to 10mm, hand-sanded inside and at the rim, set into 19mm untreated Western red cedar with a solid rear panel and a copper roof overhanging the face so the entrances stay dry. £39.99 with free worldwide shipping and a 30-day money-back guarantee.
Built to the standard this guide describes
Untreated Western red cedar, a hand-formed copper roof, tunnels from 2mm to 10mm sanded mirror-smooth, and a solid rear panel. From £39.99 with free worldwide shipping and 30 days to change your mind.
