Why solitary bees are worth the bother

Britain has around 270 species of wild bee, and the overwhelming majority of them are solitary. There is no queen, no hive, no swarm — just a single female who mates, finds a suitable tunnel, lays a series of eggs and provisions each one with a ball of pollen and nectar before sealing it up. She never meets her offspring.

Roughly a third of our solitary bees nest in hollow plant stems or in old beetle borings in dead wood. That is exactly the habitat that tidy gardening removes: strimmed hedgerows, shredded prunings, fallen trees cleared away and every last stem cut back in autumn. A bee hotel is a poor substitute for a scruffy corner of real woodland, but it is a genuinely useful one. Built properly, it will fill with red mason bees in spring and leafcutter bees by midsummer, and you will see the neat mud plugs and circular leaf discs that give them away.

Pick the spot before you pick up a drill

Position matters more than carpentry. Solitary bees are cold-blooded and need warmth to fly, so a hotel in the shade will sit empty however well you build it.

• Face it south or south-east. A wall, fence or shed that catches sun for most of the day is ideal.
• Get it up off the ground. Between one and two metres is comfortable — warm, but out of reach of damp and splashing.
• Give it a roof. A generous overhang, or the shelter of eaves, keeps driving rain off the tunnel openings.
• Keep it away from bird feeders and nest boxes. Blue tits and great tits will happily pick larvae out of a hotel if it is within easy reach of a perch.
• Angle it very slightly forward. A two or three degree tilt downward stops rain running in, but keep it near level so bees can walk in.

Avoid a north-facing wall, a spot under dripping guttering, or anywhere the hotel will sit in permanent shade from a hedge.

Wood, stems and the things to leave out

The traditional bee hotel is a block of timber drilled with tunnels, sometimes bundled with hollow stems alongside it. Both work well if the materials are right.

• Untreated hardwood for blocks — oak, ash, beech or sycamore. Softwoods such as pine splinter, bleed resin and leave a furry inside surface that damages delicate wings.
• Hollow stems — bamboo canes, cut just beyond a node so one end is naturally sealed, plus teasel, reed, dock and bramble. Elder works if you push out the pith with a stiff wire.
• Avoid glass and plastic tubing, which condense water and grow mould; MDF and plywood, which swell and crumble; and any timber that has been stained, varnished or pressure-treated.

Every tunnel must have a closed back. An open-ended tube is a wind tunnel, not a nest.

Drilling a block that bees will actually use

Use a sharp bit and sizes between 5mm and 10mm. An 8mm tunnel suits red mason bees; 5mm and 6mm attract the smaller species such as yellow-faced bees. Drill to a depth of 100–150mm, and never right through the block. Space the holes about 15–20mm apart so the timber does not split.

Run the drill slowly and withdraw it often to clear the dust. When you have finished, sand the face of the block so the entrances are clean and splinter-free, and tap it firmly to shake out loose debris. The tunnels should feel smooth when you run a fingertip inside — rough walls mean the female has to work harder and the eggs are more likely to be damaged.

For a stem bundle, pack canes tightly into a piece of drainpipe or an open-fronted box so there are no gaps between them. Gaps attract mites and parasitic wasps, which will raid the nests. You can mix diameters in one bundle, but group similar sizes together so the face is even and easy for bees to find.

Cleaning and care through the year

Once bees move in, leave the hotel alone. Between spring and late summer the tunnels are full of developing larvae, and moving or knocking the box can dislodge them. Mason bees emerge from March onwards, leafcutters a little later. Watching a capped tunnel for the first time is one of the quiet pleasures of a British garden.

Clean gently each autumn, once the bees have emerged and the weather turns. Empty the hotel and work through it methodically:

• Tip out used stems and replace them. Bamboo that has split or gone soft harbours mould, and old tunnels accumulate parasites, so fresh canes each year are worth the small effort.
• Scrub drilled blocks with a bottle brush to clear out mud, pollen and silk. For a deeper clean, use a weak bleach solution of one part bleach to nine parts water, rinse thoroughly and dry the block in full sun for a day or two before returning it.
• Check the fixings, roof and any mesh. Repair before winter rather than after.
• Store spare blocks somewhere cold, dry and ventilated — a shed is fine, a sealed plastic box is not.

Then put the kettle on, leave the stems long in one corner of the garden, and let the woodpile go a little untidy. The hotel does good work, but it is the surrounding scruff that keeps the bees coming back.