Building a bug hotel from garden materials

Why a bug hotel earns its place in the garden

By the time October arrives, most of us are thinking about putting the garden to bed. But for the insects that have spent the summer pollinating your courgettes and quietly munching their way through the aphids in your borders, autumn marks the start of the hardest stretch of the year. A bug hotel — sometimes called an insect hotel or a wildlife stack — gives those creatures somewhere dry, sheltered and safe to sit out the cold months. Build it well and you will notice the difference next spring: more solitary bees working the apple blossom, more ladybirds on the roses, and fewer greenfly than you would otherwise have to deal with.

The secret is not to think of it as a single object. A good bug hotel is really a collection of small habitats packed into one frame, because a lacewing wants something completely different from a mason bee. Get the materials right and you will attract a genuinely useful mix of residents.

Choose the right spot before you build

Position matters far more than size. A modest hotel in the right place will outperform a grand one in the wrong one every time.

Pick a spot that is sheltered from prevailing wind and gets some sun, ideally morning sun with a little dappled shade later in the day. South or east-facing walls are usually ideal. Avoid anywhere that bakes in high summer, and avoid the bottom of a slope where water sits after rain. Standing water is the enemy of most overwintering insects.

Lift the hotel off the ground — 30cm to a metre is plenty — using bricks, breeze blocks or a sturdy post, so damp cannot rise into the materials. Keep it away from bird feeders and nest boxes, where the traffic will put off your residents. And if you can, place it near a hedge, a log pile or an untidy corner of the border, so insects have somewhere to retreat to as soon as they emerge.

Building a frame that lasts

You do not need to spend money. An old pallet, a stack of bricks, a wooden crate or a length of untreated timber will all do the job. What matters is that the frame is untreated. Tanalised timber, creosote, gloss paint and varnish can all harm the very creatures you are trying to help, so leave them out.

Give the whole structure a roof with a generous overhang — a piece of slate, a sheet of corrugated plastic or a slab of spare timber will do. The aim is to shed rain away from the open ends of the compartments, because a soggy bug hotel quickly becomes a mouldy one. Build it 20 to 30cm deep if you can, and divide the interior into sections of different sizes rather than one big cavity.

Hollow stems for solitary bees

This is the compartment most people get wrong, and it is worth doing properly. Solitary bees — mason bees, leafcutter bees and their relatives — lay their eggs in hollow tubes, sealing each one with mud or chewed leaves.

• Use bamboo canes, cut buddleia, elder, teasel or spent sunflower stems.
• Cut them into 10–20cm lengths and bundle them tightly so the open ends face outwards.
• Leave one end open and one end closed. A tube open at both ends is useless to a bee.
• Vary the diameters from 3mm to 10mm, as different species have different preferences.
• Never use plastic drinking straws. They trap condensation and the larvae drown.

Pack the bundle so the stems do not rattle, and push it into the frame so the cut ends sit flush with the front.

Dead wood, bark and dry leaves

A section of dead wood is the single most valuable thing you can add. Beetles, woodlice, centipedes and solitary wasps all use it, and the decaying timber itself supports the fungi and invertebrates that feed a whole food chain.

Take a log of untreated hardwood — oak, ash, beech or apple are all good — and drill holes of varying sizes between 2mm and 10mm into the end grain. Stand it upright or lay it flat with the holes angled very slightly downwards so rain cannot collect inside. Bark, twigs and small branches stacked loosely will be taken up by beetles and overwintering spiders.

Dry leaves deserve their own compartment. Pack them loosely rather than compressing them, because hedgehogs, frogs and toads may use a deep leaf litter to hibernate, while lacewings and ladybirds shelter in the drier layers. A handful of corrugated cardboard rolled into a tube is also excellent for earwigs and lacewings, and costs nothing.

Looking after it through the year

Autumn is the best time to build, so the hotel is ready for insects looking for a winter refuge. Once it is up, resist the urge to fiddle.

• Check it in early spring, and replace any material that has gone damp or mouldy.
• Leave it undisturbed from late spring through summer, when bees may be nesting inside.
• Keep the surrounding area a little untidy. Seed heads, leaf litter and spent stems are all part of the habitat.
• Never spray insecticides anywhere near it. A bug hotel next to a sprayed border is a trap, not a refuge.

Do those small things and your hotel will quietly fill up with residents. The reward is a garden that looks after itself a little better each year, with less spraying, more pollination and a great deal more life in it.