Planting Wildflowers for Insects That Feed Swifts

Swifts arrive in Britain through May and are gone again by the middle of August, and everything they do in that short season depends on one thing: airborne insects. A pair raising chicks can bring in thousands of tiny insects a day, caught on the wing at anything from rooftop height to a thousand feet up. When the weather turns cool and wet, they drop lower and hunt over gardens, allotments, parks and playing fields — which means the insects in your patch of Britain genuinely matter.

Why Swifts Are So Reliant on Insects

Swifts feed almost exclusively on what ecologists call aerial plankton: small invertebrates drifting on the breeze. Think aphids, midges, small flies, hoverflies, craneflies, moths, tiny beetles, winged ants and even spiders that have ballooned up on threads of silk. Most prey items are between two and ten millimetres long, and a swift needs a great many of them. Nestlings are fed constantly in daylight, and a run of cold, drizzly days can mean chicks go hungry or are ejected from the nest by desperate adults.

Because so many swifts nest in towns and villages, urban and suburban insect numbers are just as important as farmland ones. Survey data suggest British insect abundance has fallen sharply in recent decades, and that loss shows up directly in swift numbers. The good news is that insects respond quickly to food and shelter. A wildflower patch is one of the fastest ways to put both back into the landscape.

What Makes a Good Swift Larder

Diversity beats sheer volume. A scruffy mix of native wildflowers, long grass, seedheads and undisturbed soil supports far more insects than a neat border of bedding plants, and it keeps producing from spring through to autumn. Aim for three things:

• Nectar and pollen for adult hoverflies, bees, moths and beetles, so they can breed and lay eggs.
• Leafy larval food plants for caterpillars, sawfly larvae and aphid colonies — the soft, sappy growth that ends up as swift food.
• Structure left standing over winter, so seedheads, hollow stems and untidy corners shelter insects through the cold months.

Peak demand runs from May to August, so what matters most is a continuous chain of flowers through early, mid and late summer rather than one glorious fortnight in June.

Wildflowers That Earn Their Place

Stick to British native species and single-flowered varieties. Double flowers often have little or no nectar and are a waste of space. Plenty of reliable choices do well in ordinary garden soil:

• Open, shallow flowers: ox-eye daisy, yarrow, wild carrot, field scabious, common and greater knapweed. These are magnets for hoverflies and small flies, the bread and butter of a swift's diet.
• Clovers and trefoils: red clover, white clover and bird's-foot trefoil. Their foliage feeds caterpillars, and their flowers keep bees and beetles busy for weeks.
• Umbellifers: wild carrot, wild parsnip, fennel, parsley and angelica. Flat, landing-pad flowerheads that hoverflies adore — and hoverfly larvae eat aphids, so they earn their keep twice over.
• Late-summer stalwarts: teasel, viper's bugloss, wild marjoram, purple loosestrife, hemp agrimony and tansy. These bridge the gap in July and August, exactly when chicks are hungriest.
• Night-scented plants for moths: evening primrose, night-scented catchfly and honeysuckle. Moths fly after dark and again at dawn, and swifts are out early.

Making the Planting Work

Wildflowers want sun and poor soil. Resist the urge to dig in compost or fertiliser — rich ground grows lush grass that swamps everything else. Rake an area of bare ground in autumn, scatter seed thinly, and tread it in so the seed makes contact with soil. If grass is a problem, sow yellow rattle alongside; it parasitises grass roots and opens up space for flowers.

Plugs are the easier route on heavy clay or in a small garden. A large pot of wild marjoram, wild carrot and field scabious in full sun will pull in insects all summer. Whatever you plant, put the mower away from part of it. Cut half the patch in late August or September and remove the clippings, then leave the rest standing until spring so seedheads feed birds and stems shelter overwintering insects. Never spray pesticides nearby, and keep a shallow dish of water or a muddy puddle for insects to drink from.

Community Spaces and Shared Ground

Verges, churchyards, school grounds, allotment edges and the strips beside car parks can all become insect corridors. A parish council is often surprisingly open to a trial wildflower strip if you offer to help manage it and put up a small sign explaining why the grass looks untidy. Staggered cutting — one section short, one long, swapping each year — keeps the space looking cared for while still giving insects somewhere to live.

Talk to neighbours, the local wildlife trust or a community group, and think in terms of linking patches rather than perfecting one. Three small plots along the same street are worth more to swifts than one immaculate meadow, because insects can move between them and swifts can hunt along the whole line.

Getting Started This Season

Autumn is the best time to sow, ideally between late August and October while the soil is warm. Spring sowing works too, though you may see fewer flowers in the first year. Expect a slow start: most wildflower patches take two or three summers to hit their stride. Keep them watered through their first dry spell, weed out the thuggish grasses, and be patient.

Then, on a warm June evening, stand outside and look up. Those dark, scythe-winged shapes screaming over the rooftops are feeding on the insects your flowers helped raise. It is a small, satisfying connection to make — and one that every garden, verge and window box in the country can play a part in.