Seeds of change: Summer is coming to a close, but the garden can still provide delights

Just scatter seeds of love-in-a-mist or some bright Californian poppies, says Anna Pavord.

You can't garden without being an optimist. So, despite the fact that I'm still waiting for the slug-ravaged remains of our tobacco plants to move on from the state in which I planted them out in May, I've already started on a new round of seed sowing. There's a big bunch of flowers, wonderful for cutting, that you can start off now in the hope that next season is going to be a flowery triumph.

Some flowers, once you have introduced them into your garden, go on introducing themselves whether you want them or not. There's a fast-draining part of our garden, penned in behind a retaining wall, south-facing, sunny, covered in 6mm gravel, that I use for special bulbs – species tulips, iris, little crocus. But these are all spring delights and I don't want to look at a barren gravel bank all summer. But nor do I want to introduce anything that will seriously interfere with the bulbs baking (as much as they are able) during the summer.

As an experiment, when we first arrived here, I scattered some seed of love-in-a-mist over the gravel, at about this time of the year. They germinated that same autumn and by spring were well established. The advantage of love-in-a-mist is that, unlike many annuals, it has more than just its flowers to offer. The balloon seedheads are superb, and if you cut some now and hang them upside down to dry, they'll provide the underpinning for plenty of flower arrangements during the winter. And thef foliage of love-in-a-mist is light and feathery, attractive to look at, but also good in terms of the bulbs. It doesn't shade out the ground.

Since that first sprinkling of seed, I've never been without nigella. In fact, it's trying to take over the path as well as the bank. The path is rammed stone, set in sand and the spaces between the stones are already thick with the bright wispy green of next year's flowers. Recently, I've added Nigella hispanica to the mix. It comes into bloom slightly later than the standard form (Nigella damascena) and the flowers are much darker blue. The seedheads are better, too, vase-shaped rather than round, with nine very pronounced horns sticking out round the edge of the vase. It's a great plant and you can get several forms from Chiltern Seeds. 'Midnight' (£2.14) has extra dark flowers, 'African Bride' (£2.13) has white flowers, each with a showy boss of purplish-black stamens. Both of these grow to about 1m (36in).

With nigella, the best way to sow seed is to scatter it direct on the ground where you want the flowers to grow. Gravel might seem a harsh kind of seedbed, but as the seedlings on the path show, nigella, which comes from arid areas in Spain and North Africa, seems rather to like it.

So does the Californian poppy, Eschscholzia californica, though it doesn't seed around as liberally as nigella. Its long, cranebill seedpods have been shedding their load on the gravel bank for the past month, but my guess is that mice eat more of these than they do of the other. Each year, at this time of year, I add an extra sprinkle of some named form of Californian poppy: 'Ballerina' (£2.03 from Chiltern Seeds), a mixture of doubles and semi-doubles, or 'Thai Silk Apricot' (£2.49), shorter than the standard kind with flowers of a soft creamy yellow. If you cut eschscholzia early in the morning before the wrapped buds have unfolded themselves, the flowers will last several days in a vase.

Opium poppies grow on the gravel bank too, though they've now all been pulled up. Unfortunately the leaves of this poppy look hideous towards the end of summer, brown and wrinkled with all the appeal of dirty floor cloths. As soon as the pepperpot holes open up around the crown of the seedhead, you can pull up these poppies and shake them around where you want them to grow next year. After all, you are only imitating nature's own timing. Avon Bulbs have started offering carefully chosen flower seed and they have six different opium poppies (£2.50 a packet) including double white, lilac and black varieties. I've ordered the one called 'Flemish Antique' with white petals feathered and stained with deep pink. I've seen it in flower and it is ravishing.

Other flowers are best sown now in pots of compost and pricked out later in autumn. This is how I grow blue cornflower, and the two magnificent cow-parsleyish annuals, ammi and the orlaya which played a star part in Cleve West's Chelsea garden this year.

It would also be the best way with a few other annual flowers, good for cutting, that are best sown round about now: the quaking grass Briza maxima, English marigolds (Calendula officinalis), clarkia, annual coreopsis, godetia, delphinium-like larkspur (Consolida ajacis), annual scabious such as the nearly black 'Ace of Spades' (Thompson & Morgan £2.89) and fragile-looking Shirley poppies. I've had success with autumn-sown snapdragons, too, leaving the pots of seed in the cold frame over winter and pricking out the seedlings in spring.

Of course, you can sow any of these in spring, too, but there's a lot else to do then and the weather is often more capricious. The earth is usually warmer in autumn than it is in spring, which favours direct sown seed.

If you are really mad about a plant, as I am about Ammi visnaga, then you can sow in both seasons. The autumn-sown plants will come earlier into flower, but the spring ones will extend the season, right on until the first frosts. Avon are offering Ammi visnaga 'Mystique' (£2.50) which makes a terrific cut flower, if you strip off all the leaves first (they turn an unpleasant yellow in a vase).

I like A. visnaga more than A. majus. The densely-domed flowerheads make more of an impact and the foliage is better: light, feathery and bright. But all are good and, as I am sowing, I like imagining how I'm going to use them in the coming season: ammi taking over from aquilegias; ammi providing airiness between the blocky stems and big white trumpets of Lilium longiflorum; ammi pushing through the grey-blue thistles of eryngium. That last is what they are doing at the moment and it is a trick worth repeating.

Avon Bulbs: 01460 242177, avonbulbs.co,uk; Chiltern Seeds: 01229 581137, chilternseeds.co.uk; Thompson & Morgan: 0844 573 1818, thompson-morgan.com