Our garden editor Clare Foster on the seeds to sow in September

In an article from her website Bud to Seed, Clare Foster discusses the seeds you can sow even as autumn gets underway.
Sabina Ruber

There is something defiant about sowing seeds at this time of year. As the year starts tapering, the days shortening, it seems counter-intuitive to be doing something most of us associate with spring, but it feels so good to have trays of emerging seedlings as the autumn turns into winter. The main group of plants to sow now are the hardy annuals - which you can also sow in early spring. Sowing them in autumn gives you a head start and generally produces taller, more robust plants about a month earlier than spring-sown plants. Plants like Ammi majus, such a stalwart in my summer border, are consistently better when sown in autumn - in my garden they self sow too, but I like to have a supply of pot-raised plants in the wings to plant out in early spring wherever there are gaps in the border.

Other annuals that can be sown now include marigolds, cornflowers, larkspur, nigella and poppies. You can direct sow all these if you like, but I prefer to sow most in seed trays, potting them on over winter or in early spring, just because of the attrition rate of sowing directly into the ground. Having said that, poppies in particular don’t like their roots disturbed so I always sow these direct, using the non-scientific scatter-and-see method with mixed results!

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I’ve just sown a tray of Ammi using seed I collected from this year’s crop. Using a modular tray, I sowed two or three seeds to a module (in multi-purpose compost because I couldn’t get any seed compost), and will remove the weaker seedlings to leave one strong one to fill the module. I’ve left it outside, protected by a clear plastic lid, but will move it into my unheated greenhouse when the weather gets colder for some protection. If you don’t have a greenhouse, use a cold frame, mini greenhouse, unheated conservatory or a shed with a window. These will grow quite swiftly to start off with, so I will pot them on into 9cm pots before Christmas, and then plant them out in March.

I’m also sowing some honesty, Lunaria ‘Corfu Blue’ which is a biennial. The received wisdom is that you should sow biennials in June or July, so that they flower the following year. I think if I sow it now, it may not flower until 2022, but I want some more plants for the back border, so I think it’s worth getting them started now.

Sabina Rüber

Other plants like foxgloves are easier to germinate if the seed is fresh, so I am sowing seed of the perennial Digitalis grandiflora, which I have just collected from my plants in the garden. The seed is tiny, so I’ll sow this on the top of some finely sieved compost in a seed tray and prick out the seedlings when they are big enough into small pots to overwinter in the greenhouse. Many of the umbellifers will also benefit if sown fresh, so I will also sow some Cenolophium denudatum from seed I collected today. It’s self seeding everywhere in my garden so I don’t really need more plants - but they will be given away to friends or sold at my next charity plant sale. Last but not least, I collected a huge amount of seed from my Dianthus carthusianorum today. This is so easy to grow from seed, but I have only sown it in spring before, so I’m going to give it a go in autumn too. Trial and error is my mantra in gardening.

See Clare's book The Flower Garden for her favourite flowers to grow from seed, and visit her website budtoseed.co.uk for many more articles on gardening throughout the year.