Why Autumn Matters More Than You Think

By the time September arrives, most of us have stopped thinking about the border. The bedding has gone over, the roses are looking tired, and the temptation is to retreat indoors with a cup of tea and leave everything until spring. Resist it. The work you do between now and the first hard frost is what decides whether next year's border romps away or limps along.

In a small garden this matters even more. When every square metre is doing three jobs at once, the soil is worked harder, plants are packed closer together and roots compete for every drop of water and nutrient. Autumn is your chance to reset that balance. None of the jobs below take long, and most of them cost nothing at all.

Clear Fallen Leaves — But Don't Waste Them

Leaves left thickly on a border do real harm. They smother low-growing plants, trap damp against crowns and give slugs and snails somewhere snug to overwinter. On a heavy clay soil they can also form a soggy mat that blocks light and air completely.

Clear them regularly rather than waiting for one big tidy-up. A light rake between plants is usually enough, and a pair of gloved hands works better than a tool where the border is tightly planted. Pay particular attention to alpines, small bulbs and anything with a low rosette of leaves — these suffer most.

Don't bin what you collect:

• Fill a bin bag or old compost sack, punch a few holes in it, and leave it tucked behind the shed for a year. You'll have leaf mould, one of the finest soil conditioners you can get.
• Use dry leaves as a winter mulch over bare soil, but keep them a hand's width away from plant stems.
• Shredded leaves rot down faster, so run the mower over them on the lawn before collecting.

If you only do one job this month, do this one.

Divide Perennials That Have Outgrown Their Space

In a small border, plants that were perfectly behaved three years ago are now elbowing their neighbours. Autumn — specifically October and early November, while the soil is still warm — is the ideal moment to lift and divide herbaceous perennials. They settle in before the cold, and you get free plants into the bargain.

The signs are easy to read: a dead patch in the middle of the clump, fewer flowers than last year, or stems flopping outwards. Lift the whole clump with a fork, working around it to avoid spearing the roots, then split it with two forks back to back or a sharp spade. Replant the healthiest outer sections and compost the woody centre.

Good candidates include hardy geraniums, asters, heleniums, daylilies, sedum and most ornamental grasses. Leave anything that flowers in early spring — primroses, pulmonarias, hellebores — until after they've bloomed, or you'll sacrifice next year's display.

Replant at the same depth they were growing before, firm the soil gently with your boot, and water well even if rain is forecast. In a tight border, be ruthless: keep a clump only as wide as you can afford to give it.

Mulch Bare Soil Before the Frosts Bite

Bare soil is vulnerable soil. Winter rain pounds it flat, frost lifts it, and weeds find every gap. A layer of mulch does three jobs at once — it insulates roots, suppresses weeds and slowly feeds the soil as worms pull it down.

Wait until the ground is damp but not waterlogged, and until you've done your dividing and planting. Then spread a generous layer, roughly 5–7cm deep, over any exposed ground. Keep it clear of stems, crowns and the trunks of shrubs; piling mulch against bark encourages rot.

What to use depends on what you have:

• Well-rotted manure or garden compost — best for hungry borders and clay soils, but don't use fresh manure, which burns roots.
• Bark chippings — long-lasting and neat around shrubs, though slow to break down.
• Leaf mould — perfect for woodland plants and light, sandy ground that dries out quickly.
• Gravel or grit — ideal around alpines, Mediterranean herbs and anything that hates a wet crown.

If you're gardening in pots, this is the moment to raise them onto feet or bricks so they don't sit in standing water all winter.

Tidy, Cut Back and Plant for Spring

Not everything needs cutting down. Seedheads on teasels, echinops and sedum feed the birds and look superb rimed with frost, so leave them standing. But do remove soggy, diseased foliage — especially around roses and peonies — and clear any annuals that have finished.

Once the border is tidy, there's still time to plant. Autumn is the best season for bare-root and container-grown shrubs, and for bulbs. Tuck snowdrops, crocus and dwarf narcissi into any gaps between perennials; in a small space, planting in layers like this squeezes far more out of the same patch of soil.

Finish by sharpening your secateurs, emptying and cleaning your pots, and making a note of what worked. Then put your feet up — you've earned it, and your border will thank you come March.