What to plant in October

October is the quietest month for sowing and one of the most important for planting, and the two are not the same thing.

Very little seed will germinate outdoors now - the soil is cooling through 10C in most of the country and heading down. But the crops that go in this month are the ones you cannot plant at any other time of year and still get a decent result: garlic, broad beans, and overwintering onions. Miss October and you either take a much worse crop in spring, or you do not get one at all.

Check today's soil temperature before you commit. It is the number that decides whether anything you sow this month comes up, and in October it varies by more than 5C between the south coast and the north of Scotland.

What can I plant in October?

Garlic, broad beans, overwintering onion sets, and fruit. The seed catalogue is mostly closed; the planting season is wide open.

Garlic is the headline crop of the month. It needs a period of cold - roughly a month below 10C - before it will split into cloves at all, so it is planted now and harvested next summer (RHS garlic guide). Split the bulb into cloves on the day you plant. Pointed end up, 2 to 3cm deep, 15cm apart, 30cm between rows. Solent Wight is the dependable softneck for most of the UK and stores through to spring. On heavy, wet soil, start the cloves in modules and plant them out in November - garlic sitting in cold water rots.

Broad beans go in from late October and this is the month they have been waiting for. An autumn-sown broad bean crops in May and June, three to four weeks ahead of a spring sowing, and it usually escapes blackfly entirely because it is already flowering by the time the aphids arrive. Aquadulce Claudia is the variety bred for it - almost nothing else is properly hardy enough. Sow 5cm deep, 20cm apart, in double rows 20cm apart (RHS broad bean guide). Do not sow early - a bean that gets too big before the cold hits is a bean the frost kills.

Overwintering onion sets can still go in during the first half of the month. Radar and Senshyu Yellow are the two to look for. Tip just showing, 10cm apart. They root before the freeze and give you onions in June, weeks before spring-planted sets are ready (RHS onion guide). After mid-October, garlic is a safer bet than onions.

Winter salads under cover. Nothing much will germinate outside now, but corn salad, mizuna, mustards and winter lettuce sown in a cold frame, an unheated greenhouse or under a cloche will still come up and will feed you from December. The cloche is doing one job: keeping the soil a few degrees warmer, which is the whole difference between germination and rot.

Fruit. October and November are the best planting months of the year for bare-root fruit trees, raspberry canes, currants and gooseberries. The soil is still warm enough for roots to establish, and the plant is dormant so it does not have to support any top growth while it does. A bare-root tree planted now is cheaper than a container one and will nearly always outgrow it.

Rhubarb and garlic's quiet cousins. Rhubarb crowns split and replant well this month. So do chives, and this is the moment to divide any overgrown perennial herbs.

Is it too cold to sow anything outside in October?

For most crops, yes - but it is the soil that decides, not the calendar.

Most vegetable seed needs soil above about 7 to 10C to germinate reliably. In early October, southern England is often still at 12 to 14C at seed depth and a sowing of corn salad or winter lettuce will come up fine. By the end of the month, most of the country is at 8 to 10C and germination is slow and patchy. In the north it is already marginal at the start of the month.

The practical test: if the soil at seed depth is above 10C you can still direct-sow hardy salads. Below that, use a cloche or sow in modules somewhere sheltered and plant out when the seedlings are up. Broad beans and garlic are the exceptions - they are not germinating for warmth, they are rooting for cold, and they go in regardless.

What should I be harvesting in October?

The last of the summer and the first of the winter, in the same week.

Squash and pumpkins must be cut before the first frost. Leave a good length of stalk, and cure them somewhere warm and dry for ten to fourteen days before storing. Cured properly they keep until February. Stored damp, they rot by Christmas.

Maincrop potatoes should all be lifted by the end of the month. Any left in the ground are feeding slugs, not you.

Apples and pears - the late varieties. Store only the unblemished ones, in a single layer, somewhere cold and dark.

Leeks, parsnips, kale, Brussels sprouts, chard. These are just getting going. Parsnips are markedly sweeter after a frost - the plant converts starch to sugar as an antifreeze, so leave them in the ground and lift as you need them.

The last of the outdoor tomatoes. Pick everything, green or not. The green ones will ripen on a windowsill or become chutney.

What is too late to plant in October?

Be honest about these:

• Spring cabbage - it needed sowing in August. Plants raised earlier can still be transplanted in the first week, but sowing now gives you nothing.

• Winter salads outdoors, uncovered - the soil is too cold in most of the country. Under a cloche, yes. In the open, only in the far south and only early in the month.

• Onion sets after mid-month - not enough warmth left for them to root before the freeze. Plant garlic instead.

• Anything tender - obviously, but it bears saying. The first frost in most of the UK falls between mid-October and mid-November.

What should I do with the beds in October?

Cover them. Every bed, without exception.

Bare soil over a British winter loses nutrients to the rain, slumps and compacts under the weather, and grows a crop of weeds you will have to deal with in March.

The three options, in order of value: sow a green manure (grazing rye still germinates in cold soil right through October and holds onto the nitrogen that would otherwise wash out); mulch with 5cm of compost and let the worms take it down over winter (RHS mulching guide); or cover with cardboard if you have nothing else, which is not as good but is far better than nothing.

What you should not do is dig it over and leave it rough for the frost to break down. That advice belongs to a different era of gardening. It wrecks the structure the worms have spent all year building and it leaves the soil naked in the wettest months of the year.

October is also the best month of the year to make a new bed for next season. Cardboard on the grass, compost on top, walk away - by March it is ready to sow into and you never touched a spade.

October in one afternoon

• Get the garlic in. It is the easiest crop on the plot and it only works if you plant it now.

• Sow Aquadulce Claudia broad beans in the last week. Beans in May, and no blackfly.

• Cover every empty bed - green manure or compost, never bare.

• Order bare-root fruit while the choice is still good. It will arrive in November and plant in an hour.

October feels like the end of the year. It is actually where next year's early crops are decided.