Whether solitary bees use a bee hotel depends on tube diameter, length, material and timing. Poorly designed shop-bought hotels get these wrong. Put one up in late winter or early spring, with tubes of mixed diameter about 15cm long and closed at the back, made from untreated breathable material, under a deep roof, on a south or south-east wall.
Timing: be up before the bees are house-hunting
Red mason bees are seen from April, sometimes late March, to June, with the males appearing first and the females slightly later, and adults fly for around eight weeks. A hotel put up in April is competing with every hollow stem and old nail hole already in the garden, and a female that has found and sealed a nest elsewhere will not come back to check a new one. Leafcutter bees are active later, from late spring to late summer, so a hotel hung in good time is not wasted if the mason bees pass it by.
Emergence is temperature-driven. A study of two mason bee species found that both emerged earlier after warm overwinteringKeeping a plant alive and intact through the cold months, whether left outdoors, moved under cover, or stored dormant. Full definition → and later after cold, so a slow, cold Scottish spring is likely to push emergence later. Late winter to very early spring is the practical deadline.
Diameter and length
Tube diameter decides which bees use a hotel. To attract a range of species include holes of 2 to 10mm, with 3 to 5mm the most-used size. Tubes wider than 10mm are too large for many bees.
| Hole diameter | Use |
|---|---|
| 2-5mm | Smaller solitary bees; 3-5mm is the most used size. A hotel with only large holes shuts these out. |
| 6-10mm | Larger bees such as the mason bees, which are usually first to occupy a hotel in spring; leafcutters, active later, leave neat semicircular leaf cuts sealing the cells |
| Over 10mm | Too large for many bees and likely to go unused |
A hotel with only one diameter attracts only one kind of bee, so mix sizes. Once a bee turns up, the solitary bees guide helps identify it.
Tubes should be around 15cm long with a dead end, not open at both ends. Tubes under about 15cm (six inches) can skew the offspring towards males, and holes drilled into wood should stop short of the far side. Female eggs are laid at the back of the tunnel and male eggs nearer the entrance.
What the tubes are made of
This is where many commercial hotels fail. Plastic and cardboard tubes can increase condensation. Poorly designed hotels can be fatal to their occupants. Damp trapped in sealed tubes encourages fungus, disease and parasites that spread from one packed-in tube to the next.
| Material | Verdict | Why |
|---|---|---|
| Plastic or glass tubes | Avoid | Non-porous; condensation has nowhere to go and the damp encourages fungus and parasites |
| Varnished, painted or treated wood | Avoid | Coatings trap moisture, and treated timber can carry chemicals not meant for a nest cavity |
| Cheap cardboard tubes with no removable liner | Avoid | They cannot be opened to check or clean, so mould and mites build up unseen |
| Untreated hollow stems: bramble, reed, bamboo | Works well | Porous and breathable, and cheap to replace each year |
| Drilled untreated hardwood blocks with smooth holes | Works well | Durable, if holes are drilled cleanly (splinters can damage wings), stop short of the back, and the block can be split or fitted with liners for cleaning |
| Paper liners inside stems, bamboo or drilled holes | Best for maintenance | A whole cocoon-filled liner can be lifted out and replaced without disturbing the rest |
Sealed or non-porous tubes are likelier to stay damp in a wet Scottish climate, which is another reason to choose breathable untreated stems or paper liners that can be swapped out.
Building the frame
A simple box of untreated, sustainably sourced timber about 1.5cm thick, about 15cm deep and open at the front, holds the tubes, with a solid back so no tube is open at both ends. Pack the tubes tightly enough that they do not rattle loose, and mix diameters rather than filling each row with one size. The structure should be robust enough to stay outdoors for several years.
Give the roof a good overhang to keep driving rain off the tube openings. A lack of overhang to disperse rainwater is linked to condensation and disease, and a flat or minimal roof is one of the commonest faults in cheap hotels.
Siting: sun, shelter, height
Face the hotel south or south-east to catch the morning sun, which solitary bees need to warm up and become active. Choose a sunny wall sheltered from rain and wind, under an eave if possible. Fix it securely, because a hotel that sways in wind is one bees avoid. Raise it off the ground, with no vegetation pressing against it, at a height where it is easy to check.
A hotel also needs forage nearby: pollen- and nectar-rich flowers through the pollinator season, free of pesticides, with willow and other early flowers particularly valuable for the first mason bees.
The red mason bee is rarer in Scotland and Northern Ireland than in England and Wales, so a quiet hotel in Scotland does not mean the build was wrong. Which solitary bees live locally is worth checking in the solitary bees guide first.
Seasonal maintenance
A bee hotel needs yearly attention, and one that cannot be opened will eventually spread disease among its own occupants.
| Season | What's happening | What to do |
|---|---|---|
| Late summer to autumn | Larvae developing inside sealed cells | Leave the hotel alone |
| Winter | Cocoons overwintering | Keep the hotel in place and sheltered through the cold months |
| Spring, before new bees emerge | The maintenance window | Check each tube for mould or mites; discard affected tubes, move clean occupied ones to a sheltered spot nearby, and replace old used tubes with new ones or fresh liners |
Most garden centre hotels cannot go through this routine, because the tubes are sealed or glued in with no removable liners. That is a design fault, not a failure of the owner.
Common questions
How many tubes should a bee hotel have?
There is no fixed number, but a handful of tubes supports only a handful of nests. A hotel with dozens of tubes across a mixed range of diameters gives more species a chance without needing to be enormous.
Will a bee hotel attract wasps as well as bees?
Some solitary wasps use similar cavities and are harmless garden predators. The bigger risk is parasitic species and fungus exploiting tubes that are never cleaned or replaced, which is another reason for regular inspection.
Can a bee hotel be too close to the house?
No. Solitary bees are not aggressive and rarely sting unless handled roughly, so a hotel on a house wall, shed or fence in a sunny, sheltered spot is fine and often the most practical option.
Why aren't any bees using the hotel?
Wrong diameter tubes, a shaded or exposed site, and poor forage nearby are the commonest causes beyond timing. Check it faces south or south-east, is sheltered from rain, and has tubes in range for local bees. In Scotland the red mason bee is rarer than further south, so the species may simply be scarce.
Do ground-nesting bees need a bee hotel?
No. A bee hotel helps only cavity-nesting species such as mason and leafcutter bees. Many other solitary bees, including mining bees, dig tunnels in soil and are helped by leaving patches of ground uncovered, not by any built structure.
Sources
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- Buglife: How to be the best bee hotel manager: Tubes over 10mm too large; tubes under six inches skew the male-to-female ratio; plastic and cardboard tubes increasing condensation; poorly designed hotels potentially fatal; south or south-east facing, elevated off the ground; lack of overhang linked to condensation and disease; replacing old tubes; putting hotels up in spring
- The Wildlife Trusts: How to make a bee hotel: Untreated wood; hollow stems of different diameters; holes of 2 to 10mm with 3 to 5mm preferred; a sunny wall sheltered from rain; cleaning once a year
- RSPB: Build a bee hotel: Tubes around 15cm long with a dead end; about 1.5cm thick timber; 15cm deep box; good roof overhang; several diameters; FSC timber
- Buglife: Red mason bee: Seen from April (sometimes late March) to June; males before females; flying for around eight weeks; rarer in Scotland and Northern Ireland
- RHS: Leaf-cutting bees: Nesting in hollow stems and bee hotels; active from late spring to late summer; semicircular leaf cuts
- RHS: Bees in your garden: Solitary bees nesting in hollow plant stems, rotten wood and beetle borings, or digging tunnels in soil
- Fründ, Zieger & Tscharntke et al.: Overwintering temperature and body condition shift emergence dates of spring-emerging solitary bees (PMC): Osmia bees emerging earlier after warm and later after cold overwintering