Why autumn deserves more of your garden time

Most gardeners treat autumn as the winding-down season, a slow retreat indoors with a mug of tea and a seed catalogue. In a wildflower or dye plant garden, it is quite the opposite. The soil is still warm from summer, the air is cooler, and rain arrives more reliably than it did in August. That combination is exactly what seeds and roots want.

There is a useful difference between autumn and spring sowing. In spring, plants pour energy into top growth to catch the light. In autumn, they build roots, quietly, out of sight, before the cold slows everything down. Many of our native perennials and biennials also need a period of cold and damp before they will germinate at all. Sow them now and the weather does that work for you, free of charge.

Sowing wildflower seed into warm autumn soil

Prepare your seedbed by clearing weeds and raking to a fine, crumbly tilth. Do not dig deeply if you can help it — turning the soil brings long-buried weed seed to the surface. Sow thinly, press the seed into the surface with a board or the back of a rake, and water gently if a dry spell follows. Wildflower seed is rarely buried; most of it needs light to germinate.

• Yellow rattle: sow in September or October at roughly one gram per square metre. It needs winter cold to germinate and it will weaken coarse grasses, giving finer flowers room to breathe.
• Cornfield annuals: cornflower, corn marigold, corncockle and poppies sown now will flower earlier and more strongly next summer than spring-sown seed.
• Perennials and biennials: oxeye daisy, common knapweed, field scabious, bird's-foot trefoil and viper's-bugloss all benefit from a natural cold spell. Sow into trays outdoors, or direct into a weed-free patch.
• Woad: a biennial, so sow now for leafy first-year growth to harvest next autumn. Weld is treated the same way.

Label everything. Autumn sowings have a long winter ahead and it is easy to forget what went where.

Divide, lift and take cuttings while the ground is workable

Clumps that have been in place three years or more will be tired and crowded. Lift them with a fork, split them with two forks back to back, and replant the healthiest outer sections at the same depth they were growing before. Oxeye daisy, yarrow, knapweed, field scabious and goldenrod all respond well. Water them in and let the rain do the rest.

Dye beds have their own autumn rhythm. Madder is best lifted after three or four years, when the roots are thick enough to be worth the digging. Rinse them, dry them somewhere airy, and store them whole — the colour deepens with age. Japanese indigo will not survive a frost, so take cuttings now, root them in water or gritty compost, and overwinter them on a bright windowsill. Calendula and dyer's chamomile will often self-sow if you leave a few flowers to run to seed.

Feed the dye beds, starve the meadow

This is the point where the two kinds of garden part company. Wildflower meadows want low fertility; richness in the soil encourages lush grass, which swamps the flowers you actually want. Give the meadow its final cut in late autumn and remove the cuttings. That single habit, repeated year after year, is what gradually reduces nutrients and builds a finer sward.

Dye plants, by contrast, are hungry. A thin mulch of homemade compost or well-rotted leaf mould over the madder, weld and woad beds will feed them through winter and improve the soil structure. Keep it away from stems to avoid rotting. Leave the wildflower areas unmulched and unfertilised.

Leave the garden standing for wildlife

Resist the urge to cut everything back. Seedheads of teasel, knapweed and sunflower are winter larder for goldfinches and other small birds. Hollow stems left at twenty to thirty centimetres give ladybirds, lacewings and solitary bees somewhere to shelter. A pile of leaves in a quiet corner will do for hedgehogs, and a stack of logs provides damp, dark cover for beetles and amphibians.

If a plant is diseased or collapsing, by all means tidy it. Otherwise, let it stand until late February or March. You will be rewarded with far more birds, insects and early pollinators next year.

Collect seed on a dry afternoon

Choose a still, dry day once seedheads have browned but before they shatter. Hold a paper bag under the stem and tap or snip the head into it. Write the species, the date and where it grew on the bag straight away — memory is a poor record-keeper by November.

Spread the seed somewhere cool and airy for a week or two, then store it in labelled paper envelopes in a cool, dark, dry place. Seed sown within a year or two germinates best. Sow a little of it now, save the rest for spring, and you will have spread the risk of a hard winter across two chances.