Why prunings make the best kind of bug hotel

Most shop-bought bug hotels are a box of drilled holes with a pitched roof and a sizeable price tag. They look charming, but they are often made from treated timber, the tubes are the wrong diameter for British solitary bees, and after two or three seasons the whole thing clogs with mould and nobody ever cleans it out. A hotel built from your own garden prunings costs nothing, suits the insects already living on your plot, and can be rebuilt in twenty minutes when it starts to slump.

The thinking behind it is simple. Beneficial insects do not all want the same thing. A red mason bee wants a hollow tube a few millimetres wide. A ladybird wants a dry crevice. A lacewing wants something ridged to tuck into. Give them a stack of different materials in one tidy corner and you will do more for your garden's pest control than any shelf of sprays.

What to gather from your cuttings

Keep a bucket beside you whenever you prune. Anything hollow, dry and clean is useful:

• Hollow stems — raspberry canes (thornless varieties are easier on the hands), buddleia, elder, sunflower, fennel, bamboo and thick perennial stalks. Cut them into 15–20cm lengths, always just below a node so one end is naturally sealed.
• Dead wood — a couple of logs or thick branch sections, ideally already a little soft and weathered. Avoid fresh timber and anything treated, painted or pressure-preserved.
• Dry leaves — two or three handfuls of last autumn's fallen leaves, still crisp rather than sludgy.
• Small twigs and bark — the fiddly bits you would normally put in the green bin.

Leave out anything thorny, anything diseased, and any stems that are still green and sappy. Those rot quickly and turn the whole stack mouldy.

Build a simple frame

You do not need carpentry skills. A wooden crate, an old pallet cut into sections, a stack of bricks, or four planks screwed into a shallow box will all do. Roughly 40cm wide, 30cm deep and 30–40cm tall is a good working size — big enough to be useful, small enough to move.

Fix on a solid back and a roof that overhangs by at least 5cm on every side. Slates, tiles or a scrap of exterior ply will keep the rain out, and keeping it dry is the single most important thing you can do. Wet tubes grow mould, and mould kills bee larvae. Untreated timber is fine; garden twine, wire mesh and old bricks are all you need to hold everything together.

Fill it in layers

Pack the materials in tightly — loose fill simply falls out and offers no shelter.

• Top section: bundles of hollow stems tied with twine, packed so the cut ends face outwards. Mix the diameters: 4–6mm suits small solitary bees and wasps, 7–9mm suits red mason bees and leafcutters.
• Middle: logs drilled with holes 4–8mm wide and about 10cm deep, drilled into the side grain rather than the end grain so they do not split. Wedge a few loose twigs around them.
• Lower section: dry leaves pushed into the gaps between logs and bricks, plus a couple of flat stones or slates laid loosely to create dark crevices for beetles and ladybirds.

Three or four small bundles placed around the garden will attract more insects than one grand construction, and if one goes wrong you have not lost the lot.

Choose the right spot

Site it somewhere warm, dry and out of the prevailing wind — a south or south-east facing wall is ideal, and morning sun helps bees warm up before they fly. Mount it at least a metre off the ground so it stays clear of damp soil and away from slugs, and give it a clear flight path rather than tucking it behind a shrub.

Do not put it in the dark damp corner you never visit. A bug hotel in shade stays wet and stays empty. If you want a shady habitat too, that is what a separate log pile and leaf heap are for — those suit beetles, woodlice, toads and hedgehogs.

One more thing: leave a small patch of bare, damp soil nearby. Mason bees line their nests with mud, and leafcutter bees need soft leaves — rose, ash and birch are favourites.

Looking after it through the year

Resist the urge to tidy. The busiest months are March to June, when solitary bees are nesting, and a hotel rearranged in spring is a hotel abandoned. Watch for neat mud plugs in the tubes in early summer and circular leaf discs a little later — both signs it is working.

The one job worth doing is a light check in late autumn. If tubes are cracked, damp or clogged with mould, pull those bundles out and replace them with fresh cuttings, once the adults have emerged. Leave everything else exactly where it is, because ladybirds and lacewings will be moving in to overwinter.

Then step away until the first warm days of March. Within a season or two you should see solitary bees queuing at the tubes, ladybirds tucked between the slates, and a good deal fewer aphids on the roses. Not bad for a pile of prunings.