Preparing Allotment Beds for Autumn Sowing and Planting

By early September, most allotment beds have that well-used look about them — bolted lettuces, mildewed courgette leaves, a few sad brassica stumps. It is tempting to walk away until spring, but the next six weeks are the most valuable of the year for putting the ground to bed. Get it right now and you will be sowing into soil that is workable, fertile and free-draining in March, while neighbouring plots are still sticky clay.

Clear Spent Crops Without Wasting the Ground

Start with the beds that have finished outright. Pull spent runner beans, courgettes, squash and sweetcorn, and stack the tops on the compost heap. There are two bits of housekeeping worth doing properly.

First, cut bean and pea haulms off at ground level rather than pulling them. The roots carry nitrogen nodules that break down in place and feed whatever follows. Second, be strict about what goes on the heap. Blighted tomato and potato foliage, clubroot-affected brassica roots and anything with white rot on onions should go into the bin or the council green waste collection — not onto your plot, where it will come back to haunt you for a decade.

Once a bed is clear, don't leave it bare and don't leave it lumpy. Rough-fork it over, remove the worst of the perennial weed roots, and decide straight away whether it will be mulched, sown or left under a cover crop.

Feed the Soil Before Winter

Autumn is the one time you can be generous without much risk. Spread two bucketfuls of well-rotted compost or manure per square metre over the surface and fork it into the top 5–10cm. No need to dig deep; worms and frost will do the rest of the work for you.

A few adjustments depending on your soil:

• Heavy clay: add compost generously and a light dressing of horticultural grit or sharp sand. Don't overdo the grit — organic matter is what actually opens clay up.
• Light sand or chalk: compost and leaf mould are your friends. They hold water and nutrients that would otherwise wash straight through.
• Brassica beds: a sprinkle of wood ash adds potash, but keep it away from potatoes and acid-lovers like blueberries.
• Waterlogged corners: consider ridging the soil or installing a raised bed before winter rather than fighting it each spring.

Leaf mould is the most underrated soil improver on any plot. Bag this autumn's fallen leaves in old compost sacks, punch a few holes, and leave them behind the shed for a year.

Sowing Green Manures for Winter Cover

Empty beds that won't be planted until spring should never sit naked through a British winter. Heavy rain pounds bare soil flat, leaches nutrients and encourages weeds. Green manures hold it all together and add organic matter when you dig them in.

• Field beans: the workhorse for November sowing. Hardy, deep-rooted and nitrogen-fixing. Sow in rows 20–25cm apart at roughly 20g per square metre.
• Winter tares: quick to establish and good on beds cleared in September. Sow at around 8g per square metre.
• Grazing rye: sow if you are late — it germinates in cold soil and produces masses of biomass. Not nitrogen-fixing, and it needs cutting back in early spring before it turns woody.
• Mustard and phacelia: useful for a fast cover before the first hard frosts, which will kill them off and leave a mulch behind.

Whichever you choose, chop the tops down in late winter or early spring while they are still soft and leafy, then leave them to wilt for a week before forking in.

Winter Salads and Early Crops to Sow Now

Not every bed needs to be shut down. With a cloche, cold frame or a sheltered spot, you can keep harvesting right through the winter.

Winter lettuce such as 'Winter Gem' or 'Arctic King', lamb's lettuce, land cress, mizuna, rocket, winter purslane and spinach 'Giant Winter' all cope with cold and short days. Sow thinly in September and early October — plants that go into winter too soft and leafy will simply rot.

For an early start next year, sow broad beans 'Aquadulce Claudia' in late October to mid November on well-drained soil, and plant garlic and Japanese overwintering onion sets. A sowing of round-seeded peas under cover in November gives you pods in June. In colder, wetter parts of the country, hold broad beans until February rather than risk losing them to rot.

Protect Bare Soil and Tidy the Paths

Any bed left empty and unsown should be covered. A 5cm layer of compost, straw or well-weighted cardboard keeps rain off, suppresses weeds and feeds the soil as it breaks down. Cardboard topped with compost is better than black polythene, which can leave soil sour and give slugs somewhere to hide all winter.

Then turn your attention to the bits everyone forgets:

• Clear leaves and weeds from paths and top up with bark chip — it saves hours of spring weeding.
• Cut back overhanging grass edges, which shelter slugs and snails.
• Check raised bed boards, stakes and netting frames, and repair them now while the ground is soft.
• Clean, dry and oil your tools, and empty and store hoses and water butts so they don't split in a hard frost.
• Leave a small pile of logs or a patch of seed heads somewhere out of the way. The birds and beetles that overwinter there will repay you by eating pests in spring.

An afternoon or two of work now, and your plot will greet you in February ready to go rather than needing rescuing.