Why waterside gardens hum with life

Any garden with a pond, a boggy corner, a ditch or a stream along its boundary will hold far more insects than a dry plot of the same size. Water keeps the air humid, softens frost, and feeds a long chain of plants that insects depend on. Damselflies hunt along the margins, caddisflies shelter in damp leaf litter, and solitary bees nest happily in banks and old timber nearby. Adding a bug hotel to that mix simply gives these creatures somewhere dry and safe to spend the winter, lay their eggs or wait out a spell of wet weather.

You do not need much room, and you certainly do not need to spend money. A bug hotel the size of a small shoebox, made from offcuts and prunings, will do a proper job if it is built and sited with a little care. Here is how I build mine, and what to put in them.

Pick a spot that is dry above damp ground

The single most common mistake is placing a bug hotel too low and too wet. The insects you are inviting need shelter from rain, not a soaking. Aim for a spot where the base sits at least 30 centimetres above soil level, facing south or south-east, and sheltered from the prevailing wind.

• Mount it on a post, a shed wall or a brick plinth rather than laying it flat on the ground.
• Keep it within a metre or two of the water, but never in the flood line of a pond or ditch.
• Choose a spot that gets morning sun and dappled afternoon shade — baking heat dries out hollow stems and kills the larvae inside.
• Fix a small overhanging roof lip, even a strip of slate or a tile, to throw rain clear of the openings.

If your garden floods in winter, raise the whole structure higher. A hotel that is submerged in January is worse than no hotel at all.

Build the box from scrap timber

Any untreated timber will do: pallet wood, old floorboards, a length of shelving. Avoid tanalised or painted wood, which can leach chemicals into a damp environment. Treated timber also tends to be splintery and hard for insects to drill.

Cut two side panels, a back, a base and a roof, aiming for a box roughly 40 centimetres wide, 30 centimetres tall and 15 to 20 centimetres deep. Screw or nail it together, then add a couple of internal shelves or dividers to create separate compartments. These let you offer different materials side by side, which is exactly what a mixed population of insects needs.

Drill a few 8 to 10 millimetre holes in the back panel before you assemble it. Solitary bees and lacewings will use them, and they stay dry even in driving rain.

Fill the chambers with hollow stems, logs and leaves

Now the enjoyable part. Each compartment gets a different filling, packed firmly so nothing rattles or falls out, but not so tightly that the openings are blocked.

• Hollow stems: cut canes, bamboo, teasel, hogweed, reed or old raspberry canes into lengths matching the depth of the box. Bundle them with the cut ends facing out and the natural, sealed ends pushed to the back.
• Drilled logs: take a piece of dead wood — willow, alder and birch are ideal near water — and drill holes of 3 to 10 millimetres across, angled very slightly upwards so rain runs out.
• Loose bark and leaves: a compartment of dry leaves, wood shavings and flakes of bark suits earwigs, beetles and overwintering ladybirds.
• Stones and gravel: a shallow tray of mixed grit gives ground beetles and newts somewhere cool to rest.
• Straw or hay: loosely stuffed, it makes a soft nursery for hoverflies and small spiders.

Leave the front open. Wire mesh across the face looks tidy but traps insects and blocks the warmth of the sun.

Plant the approach

A bug hotel works best when it has a larder next to it. Plant the strip in front with nectar-rich natives: purple loosestrife, marsh marigold, water mint, meadowsweet, hemp agrimony and devil's-bit scabious all thrive in the damp conditions beside a pond. Allow a patch of nettles and a little rough grass to stand through the winter, and leave seedheads on the stems rather than cutting everything back in autumn.

A shallow dish of water with pebbles for landing is useful too, though if you already have a pond, keep the edges gently sloping so hedgehogs and frogs can climb out.

Looking after your bug hotel through the year

Once built, a good hotel needs very little. Check it in early spring, before the first warm days bring the bees out. Clear any cobwebs from the entrances with a soft brush, and replace stems that have gone mouldy or crumbled. Do not tidy it in winter — that is precisely when most of your guests are inside, dormant and vulnerable.

If a compartment has been colonised, resist the urge to inspect it closely. Leave it alone until late spring, then top up the filling materials. Over three or four years you will see the mix shift: first solitary bees and leafcutter bees, then earwigs, then the small hunting wasps and hoverflies that follow them. That slow build of life is the real reward, and it starts with a few hollow stems and a scrap of timber beside the water.