Why bees run out of steam in a heatwave

On a hot July afternoon, a bumblebee on the pavement is not necessarily dying. She may simply be exhausted. Flight uses a huge amount of energy, and a bee's body has to stay warm to work — which is a real problem when the air around her is nudging 35°C and there is no shade for metres in any direction.

Heat also shuts down the larder. Many flowers stop producing nectar once temperatures climb, and any nectar already there evaporates or thickens until it is too sticky to drink. Lawns are mown, verges are cut, and the long grass and wildflowers that normally keep bees going through midsummer are gone just when they are needed most. Bumblebee colonies are at their peak, solitary bees are still provisioning nests, and there is suddenly far less to go round.

The result is bees grounded on paths, clinging to fence posts, or crawling slowly across paving. Most of them can be helped in under a minute.

A spoonful of sugar water — the safe recipe

The old trick really does work, but the details matter. Use white granulated sugar and cool, clean water at roughly equal parts — about one teaspoon of sugar to one teaspoon of water. Stir until it is fully dissolved. That is all you need.

Offer it in something shallow: a teaspoon, a jam jar lid, a saucer. Put a drop or two beside the bee rather than on her, in the shade if you can manage it, and let her walk over and drink. If she is on the ground, place the drop on the paving next to her mouthparts. Never dunk a bee in liquid — she will drown faster than she will recover.

If you need to move her off a hot pavement or a road, coax her onto a leaf or a piece of card and set her down somewhere cool and safe. Give her ten or twenty minutes. A bee that revives will usually groom herself, buzz, and fly off. If she is still there after half an hour, move her gently onto a flower in the shade and leave her be.

Things that do more harm than good

• Honey. Never offer it. It can carry pathogens that spread disease through wild colonies, and its sugar balance is wrong for a quick pick-me-up.
• Brown sugar, molasses, agave or golden syrup. These are harder for bees to digest and can leave them worse off.
• Artificial sweeteners. Zero calories, zero help.
• Deep dishes. Bees fall in and cannot climb out. Always give them something to stand on.
• Permanent feeders. A saucer left out for days ferments, draws wasps and ants, and can spread disease. Make it fresh, wash it, and bring it in overnight.

Shallow water stations that will not drown anybody

Bees need water, especially in heat, but they are poor swimmers. Fill a shallow saucer or tray with pebbles, marbles, corks or short twigs so there is always a dry landing place, then add water to just below the top of the stones. Set it at ground level in dappled shade — under a shrub or beside a border — and refresh it daily. Empty and scrub it every few days so you are not breeding mosquitoes.

A patch of damp soil does the same job and helps ground-nesting solitary bees at the same time. If you have a bird bath, drop a few large stones in one corner so insects can reach the water safely.

Shade, shelter and a cooler garden

The single most useful thing you can do in a heatwave is to stop tidying. Leave a patch of lawn unmown so the soil beneath stays cool and damp. Let dandelions, clover and self-heal flower — they are short of nectar but long on pollen, and they keep going when other plants give up. Leave leaf litter and hollow stems in place; they are shelter for insects that would otherwise bake.

• Keep bee hotels and insect boxes in dappled shade, never in full sun against a south-facing wall.
• Water in the early morning or late evening, and mulch borders so moisture stays in the ground.
• Leave some bare, sunny soil for mining bees, but keep it lightly damp rather than dusty.
• Avoid pesticides entirely in hot weather — residue lasts longer and foraging bees travel further for less.

Nectar and pollen that keeps flowing in the heat

Plant for a long season and you will carry bees through the worst of it. Herbs are the workhorses: lavender, catmint, marjoram, oregano, thyme, sage and borage all keep flowering in heat and are loved by every bee in the neighbourhood. Let a few bolt and flower rather than cutting them back.

For perennials, try viper's bugloss, purple loosestrife, sedum, echinacea, rudbeckia, globe thistle, teasel and cardoon. Single-flowered dahlias and cosmos earn their place in pots and borders, and a balcony with three or four flowering herbs is genuinely valuable. Avoid double flowers — the petals crowd out the nectar — and choose open, simple shapes where you can see the centre.

One tired bee on a hot afternoon is a small thing, but a garden that offers shade, a shallow drink and a succession of flowers is not. It is the difference between a colony that scrapes through August and one that thrives.