Why solitary bees and wasps deserve a place in your garden

Britain is home to around 250 species of solitary bee and a similar number of solitary wasps. Unlike the familiar honeybee, these insects do not live in colonies with a queen and workers. Each female works alone: she finds a suitable tunnel, fills it with pollen or prey, lays an egg, seals it up, and then moves on. Many of them are superb pollinators, and the wasps among them spend their days quietly hunting aphids, caterpillars and other garden pests.

The trouble is that nesting sites have become scarce. Tidy gardens, swept-up leaf litter, felled dead trees and re-pointed old walls have all removed the cracks, beetle holes and hollow stems these insects rely on. A bee hotel is a simple, cheap way to put some of that back — and it takes an afternoon to make. Build it well and it will be occupied within weeks.

Pick a dry, sunlit spot

Location matters as much as construction. Solitary bees and wasps are cold-blooded and need warmth to become active, so choose a spot that catches sun for most of the day — a south or south-east facing wall, fence or shed is ideal. Morning sun is particularly valuable because it gets the insects going early.

Mount the hotel at roughly one to one and a half metres above the ground, firmly fixed so it does not sway. Keep it dry: under a roof overhang, or with a small overhanging roof of its own. Driving rain and damp are the main enemies of the larvae inside, so avoid anywhere water collects or drips. Good air movement around it also helps.

Drilling a wooden block

A solid block of untreated hardwood is the simplest and most durable option. Oak, ash or beech are ideal; softwoods like pine split and shed splinters, which can injure delicate wings.

• Use a block at least 10cm deep, ideally 15cm, so tunnels are the right length.
• Drill into the end grain if you can — a short log section works beautifully, because the tunnels follow the grain and are less likely to crack.
• Use drill bits from 2mm to 10mm, with most holes between 4mm and 8mm. Different species need different sizes, so a mix is essential.
• Drill straight and clean to a depth of 10–15cm, leaving the back end closed. Do not drill right through.
• Space holes roughly 15–20mm apart so the walls between them stay intact.
• Blow or brush out all the sawdust, then sand the face smooth so no rough edges remain around the entrances.

Fix the block to a backboard of untreated timber and add a sloping roof. Do not paint, stain or varnish it — the smell and the chemicals deter nesting females.

Bundling hollow canes

Hollow stems are cheap and easy, and many gardeners find they are occupied faster than drilled wood. Suitable materials include bamboo, reed, elder, teasel and dried Japanese knotweed stems. If you cut knotweed, make sure it is dead and dry first, and never let it spread into your soil.

• Cut stems into 10–20cm lengths.
• Where possible, cut so a node forms the closed back wall of the tunnel, saving you from plugging the ends.
• Trim the front ends flush with sharp secateurs so there are no splinters or ragged edges.
• Pack the bundle tightly into a short length of drainpipe, a tin can, a section of guttering or a wooden frame. Loose bundles let in light and parasites.
• Fill any gaps round the outside with dry material, then secure the bundle with twine or a strap.
• Tilt the bundle very slightly forward so rain runs off, but keep it close to horizontal so the insects can walk in easily.

Make several small hotels rather than one large one. Spreading them around the garden reduces the chance that a single parasite or predator wipes out your whole population.

What will move in

Red mason bees are usually the first to arrive in spring, sealing their tunnels with neat mud plugs. Leafcutter bees follow in summer, capping theirs with discs of rose or birch leaf. You may also spot yellow-faced bees, small carpenter bees and a range of slender solitary wasps, some of which stock their tunnels with aphids or tiny caterpillars.

None of these insects is aggressive. Solitary bees have no colony to defend and will only sting if handled roughly or trapped. Watching a tunnel being carefully sealed over a few warm afternoons is one of the quiet pleasures of a wildlife garden.

Looking after your hotel

A well-made hotel lasts for years, but it needs a little attention.

• Leave sealed tunnels alone. The larvae are developing inside and will emerge the following spring.
• Do not move or clean the hotel between March and September, when it is in active use.
• In late autumn, once nesting has finished, you can move a removable block or cane bundle into an unheated shed or garage. This protects it from damp, from blue tits and woodpeckers, and from frost damage. Put it back out in March.
• Replace drilled blocks every two years and cane bundles every year or two. Old tunnels accumulate mites, mould and parasites.
• Never use insecticides, and avoid fungicides and herbicides nearby.

One final tip: avoid hotels made of plastic straws, glued tubes or a single hole size. They look tidy but perform poorly, and glued tubes cannot be cleaned. A rough, home-drilled block or a tight bundle of stems will out-nest them every time.