Sow long: If you want a beautiful cuttings garden next summer, get those seeds in now

Annual flowers are profligate with their seed. Which is why, with very little effort now, you can collect free supplies to provide next year's flowers. This summer has been superb for both producing seed (plants have grown with tremendous vigour) and ripening it. I had an unusually peaceful session with the small, thin seedpods of larkspur, cracking them open and spilling the hard black seed on to a sheet of paper on the kitchen table.

Why did I do it? Mostly because of a gloomy suspicion that because I liked the flower so much, I wouldn't be able to find it again. So before I pulled up the larkspur plants, which have performed non-stop since May, I cut off some of the seedheads, beautifully dried off in the long, hot late summer, and brought them inside.

Larkspur make excellent cut flowers, generous, many-spiked, good mixers, long-lasting. But here's another difficulty. Because they are generous, many-spiked etc, I don't want to cut them from the border, knowing they will last even longer in the ground than they do in the vase. This is where an allotment would come in handy. I could use the ground just for growing flowers to cut, without feeling I was spoiling the view from the kitchen window.

The larkspur I'm raiding for seed now were started off from seed this time last year. Autumn is a good time for sowing annuals, if you have somewhere the plants can overwinter. I've started doing a lot more since we've had the greenhouse. But the overwintering plants don't need heat. A small cold frame is enough, or you could rig up a temporary shelter on a balcony with some stiffish polythene. For some annuals, autumn is the only option. Orlaya, the lovely lopsided white flower that is another top flower for cutting, rarely germinates well in spring. It has to be sown now.

So I'm going to treat a length of the metre-wide border outside my hut like anf allotment and use it to grow flowers that I can cut without feeling I'm diminishing the effect of the garden. There's not much room, so what must come top of the list? First, I'm thinking fillers. Orlaya and ammi immediately come to mind – though you might add Ridolfia segetum if you want a greeny-yellow filler rather than a white one.

All are umbellifers, providing cow-parsleyish flowers in wide, flat heads and all are easy from seed. My own choice is Ammi visnaga, better in every way than Ammi majus. The foliage is finer, more feathery, the heads of flowers are domed and more closely packed.

I reckon I've got room for five different things and that I ought to have two 'fillers' and three different flowers to provide colour. If I didn't have it in the garden already, I might go for the spurge, Euphorbia oblongata, as a filler. By nature, it's a short-lived perennial and a very enthusiastic self-seeder. I leave clumps of it all over the place, because you can cut the odd stem here and there for a vase without missing them later.

So, cheating slightly, I'm going to use honeywort (Cerinthe major 'Purpurascens') as my second filler. The foliage, grey and waxy, is quite different in style, colour and texture to the ammi, but it's a cheat because of course it has wonderful flowers, too. Sometimes the drooping heads seem steely-grey, sometimes ultramarine and purple, strange and exotic.

The choice of flowers is more difficult as there are so many possibilities: cosmos, marigolds, tobacco plants, sweet rocket, cleome, snapdragons, sunflowers. I'm leaving out sweet peas, which I always grow on tripods for cutting, and love-in-a-mist, which seeds itself all through the border without any help from me. Both sweet williams and wallflowers are more easily bought as plants than grown from seed. So I'll go for the larkspur, with zinnias and English marigolds (Calendula officinalis). Or stocks, which would give me the added bonus of scent. Oh decisions, decisions.

Orlaya, if you are using it, is definitely best sown in a small pot now. Ammi and larkspur can be sown now or in spring. The advantage of autumn sowing is that it will give you earlier flowers next year. Cerinthe, marigolds and zinnias are best left till spring. If you are sowing in a pot, use a compost such as John Innes No 1, sow thinly and cover the seed with a thin layer of vermiculite. Water gently. The seeds don't need heat or a propagator. They'll germinate on a windowsill. Especially if you cover the pot with a pane of glass or some clingfilm to retain moisture.

When the seedlings are beyond the two-leaf stage, prick each one out into a 5cm/2in pot of compost and water them in. When the pots are full of roots, plant them out. Spring-sown seed can go straight in the ground, but it is a chancier way of getting your flowers.

FIVE TO SOW

Ammi visnaga: Height 90cm/36in. Sow now or March-Apr. Germination 14-21 days after sowing. Well-drained soil. Sun. £1.86 Chiltern Seeds

Calendula 'Touch of Red Mixed': Height 45cm/18in. Sow Mar-Apr. Germination 7-14 days after sowing. Well-drained soil. Sun. £2.15 Chiltern Seeds

Cerinthe major 'Purpurascens': Height 60cm/24in. Sow Mar-Apr. Germination 8-10 days after sowing. Moisture-retaining soil. Sun. £3.50 Chiltern Seeds

Consolida 'Blue Cloud' (larkspur): Height 75cm/30in. Sow now or Mar-Apr. Germination 10-14 days after sowing. Moisture-retaining soil. Sun. £1.85 Chiltern Seeds

Zinnia 'Benary's Giant Mix': Height 90cm/36in. Sow Apr-Jun. Germination 7-14 days after sowing. Well-drained soil. Sun. £2.20 Chiltern Seeds, chilternseeds.co.uk; 01491 824675