In September you can sow spinach, winter lettuce, rocket, oriental leaves, spring onions, radishes, chard, winter-hardy spring cabbage and green manures, and plant out garlic, autumn onion sets and overwintering broad beans towards the end of the month. It is also the best month of the year to sow a new lawn or repair a tired one, and the last sensible window for hardy annual flowers to overwinter for an early display. The trick with September is understanding that you are no longer sowing for this year, you are sowing for the hungry gap next spring.
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September used to feel like the end of things to me, packing away rather than starting. It took an old boy on the Oxfordshire site I rented to put me right. He walked past my half-empty beds one September, looked at the bare soil, and said something to the effect that an empty bed in September is a wasted March. He was right, and the year I finally listened was the year I picked spinach and salad leaves in February while everyone else was waiting for spring. September is quietly one of the most productive sowing months there is, as long as you sow the right things.
Vegetables to Sow in September
The salad crops are the easy win. Winter lettuce varieties such as Winter Density and Arctic King, along with lamb’s lettuce, rocket, mizuna, mustards and other oriental leaves, all sow happily in early September and crop through autumn, then again in early spring after a winter pause. Under a cloche or in a cold greenhouse they will keep going most of the winter. Spinach and chard sown now give you leaves in October and a heavy flush the following March. Spring onions of a hardy variety like White Lisbon Winter Hardy sit through the cold and are ready long before spring-sown ones. Radishes sown early in the month still crop in four to six weeks, and winter varieties like Mooli or China Rose sow now for pulling later. Turnips sown early September give small tender roots and useful greens. If you are not sure which varieties suit a September sowing, the vegetables to sow in September list is a useful cross-check before you order.
Two more worth knowing. Spring cabbage sown in the first half of September, then planted out in October, is the classic hungry-gap crop and one of the most satisfying things in the garden, because it grows quietly all winter and gives you greens in April when nothing else is ready. And pea shoots or hardy varieties like Meteor sown in a sheltered spot can overwinter for a very early crop, though I would be honest and say this works better in the south than the north. Timing matters more than usual in September: the first half of the month is worth far more than the last, because the soil is still warm and the light is still decent. A sowing on the 5th of September is a different proposition from the same seed sown on the 25th.
What to Plant Out in September
Planting is as important as sowing this month. Towards the end of September, garlic can go in, and garlic genuinely needs a cold period to split into cloves properly, so autumn planting gives far better bulbs than spring. Autumn onion sets go in from late September into October for a harvest weeks ahead of spring-planted ones. Overwintering broad beans like Aquadulce Claudia can be sown from late September in milder areas, though October and early November are the more usual window and honestly the safer bet in the north. Strawberry runners planted now establish through autumn and crop properly next summer rather than sulking, which is why September planting beats spring. Full detail on each in when to plant garlic, when to plant onions, how to grow broad beans and when to plant strawberries.
Flowers to Sow in September
Hardy annuals sown in September flower weeks earlier and grow noticeably stronger than the same seed sown next spring, because they make root through autumn and are ready to romp away in March. Calendula, cornflower, larkspur, ammi, nigella and poppies all suit an autumn sowing, either direct into cleared ground or in modules to plant out later. Sweet peas sown in September and overwintered in a cold frame or unheated greenhouse are a genuine step up on spring-sown plants, with longer stems and earlier flowers. September is also the month for spring bulbs: daffodils, crocus and alliums all go in now, with tulips the exception, better left until November when the soil is colder. If you are sowing a wildflower patch, autumn suits native perennial mixes because many need a cold spell before they will germinate.
September Lawn Jobs
September is the best month of the entire year for lawn work, better than spring, and most people miss it. The soil is still warm enough for fast germination but the weather is damper and cooler, so new grass establishes without the drought stress of a spring sowing. If you are sowing a new lawn or over-seeding bare patches, now is the moment. It is also the right time to scarify out the thatch, spike or aerate compacted areas, top dress with a sandy loam mix, and apply an autumn lawn feed, which is high in potash and phosphates rather than the nitrogen of a spring feed, to toughen the grass for winter instead of pushing soft growth. Do this once in September and the lawn will look better next May than any amount of spring fussing will achieve.
Other Garden Jobs Worth Doing This Month
Beyond sowing, September is about setting up next year. Clear finished crops as they come out rather than leaving beds to weed over, and either sow a green manure such as field beans, rye or phacelia, or mulch the bare soil with compost. Green manure is the underrated one: it holds nutrients that would otherwise wash out over winter, protects the soil surface from heavy rain, and gets dug in or cut down in spring. If you garden no dig, a thick autumn compost mulch does the same job and the worms do the work for you over winter. Now is also the ideal moment for improving your soil, because anything added in autumn has all winter to break down. Elsewhere: lift and dry onions and maincrop potatoes, cut down and clear any blighted foliage, order garlic and autumn onion sets before the popular varieties sell out, bring in tender herbs, and start collecting leaves for leaf mould as they fall.
The Honest Limits of September
It is worth being straight about what will not work, because optimistic sowing in September wastes seed and confidence. Anything tender is finished: no more courgettes, beans, sweetcorn, cucumbers or squash. Carrots and beetroot sown now will not amount to much outdoors, whatever the packet implies. Most brassicas other than spring cabbage are too late. And there is a real north-south split this month that generic advice tends to ignore: a September sowing in Cornwall and the same sowing in Aberdeenshire are not remotely the same gamble, and gardens in the north or at altitude should treat the first half of September as the whole month. If you are unsure whether something is worth trying, check it against the UK vegetable planting calendar, and when in doubt sow into modules or under cover rather than open ground, because a cloche is worth about three weeks of season.
Frequently Asked Questions
What vegetables can I sow in September in the UK?
Winter lettuce, lamb’s lettuce, rocket, mizuna and other oriental leaves, spinach, chard, hardy spring onions, radishes, early turnips and spring cabbage all sow well in September. Sow in the first half of the month where possible, since the soil is still warm and the light better, and use a cloche or cold frame for anything you want cropping through winter.
Is it too late to plant vegetables in September?
Not at all, but you are sowing for autumn and next spring rather than for a summer crop. Tender crops like courgettes, beans and sweetcorn are finished for the year. Hardy leaves, salads, spring cabbage, garlic, autumn onion sets and overwintering broad beans are all exactly right for September.
What flowers can I sow in September?
Hardy annuals such as calendula, cornflower, larkspur, nigella, ammi and poppies, all of which flower earlier and stronger than spring-sown plants. Sweet peas sown now and overwintered under cover are a noticeable improvement on spring sowings. September is also the month to plant daffodil, crocus and allium bulbs, though tulips are better left until November.
What should I do to my lawn in September?
September is the best lawn month of the year. Sow a new lawn or over-seed bare patches while the soil is still warm and the weather damp, scarify out thatch, aerate compacted areas, top dress, and apply an autumn feed high in potash rather than nitrogen. Grass establishes far more reliably now than in spring.
Should I plant garlic in September?
You can plant garlic from late September, and autumn planting is much better than spring because garlic needs a cold period to split into a proper multi-clove bulb. October is the more usual month across most of the UK, so late September suits colder areas and gardens with free-draining soil that will not sit wet over winter.
What is a green manure and should I sow one in September?
A green manure is a crop grown to protect and improve the soil rather than to eat, such as field beans, grazing rye or phacelia. September is the ideal time to sow one on beds that have finished, because it holds nutrients that would otherwise wash away over winter, shields the soil from heavy rain, and adds organic matter when dug in or cut down in spring.
A Sensible Place to Start
If you do nothing else this month, do three things in the first fortnight. Sow a row of winter-hardy salad leaves and a row of spinach, because they cost pennies and they will feed you when the shops are charging a fortune for a bag of leaves. Order your garlic and autumn onion sets now rather than in October, since the good varieties sell out. And do not leave a bed bare: either mulch it with compost or sow a green manure, because bare soil over a British winter loses nutrients and grows weeds. That is an afternoon’s work. The old boy on my site was right, and the March I first understood it was the March I stopped buying salad.