Muck and brassicas: Cauliflower, cabbage, broccoli - it's easy to grow your own from seed. Provided you can keep those pesky pigeons at bay, says Anna Pavord

The garden is full of activity, the rooks' even more frenetic than mine. There are already more than 60 nests swaying magisterially in the top branches of the alders that line the valley below. We do well for kindling while they are nest building. The ground underneath the trees is thick with their dropped sticks.

They have been doing a good job on de-mossing the lawn, too. They must be collecting it to line their nests. Their sociable clatter starts long before it is light when they wheel out from the trees like small dark pieces of the departing night. You can be fond of baggy-trousered, gregarious rooks. I am not sure I could ever fall in love with the more solitary crow.

And rooks, like the easiest sort of weekend guests, take themselves off during the day, feeding in different pastures. They do not, like the wretched pigeons and collared doves, expect all their meals to be provided from the one garden.

Pigeons are a particular problem with brassicas - cauliflower, cabbage and purple sprouting broccoli. Broccoli takes a long time to produce its crop and it is maddening to find the succulent spears torn to shreds just as you were thinking about eating them. Netting is the best defence, four-inch mesh, which needs to be in place by late summer and stay there until you have finished picking.

Seed of spring sprouting broccoli can be sown any time through April, though in a small garden, you may find it more convenient to wait and buy young plants later in the season. Marshalls, for instance, sends out plants of the early purple sprouting broccoli 'Bordeaux' in mid-May and also supplies the later variety 'Claret', which is dispatched from mid-July. Together they give a long season of cropping.

Unlike calabrese, which has one heavy central head, the traditional sprouting broccolis have a shower of much smaller heads. The purple kind is hardier and more prolific than the white. An early variety, such as 'Bordeaux', crops from late summer into autumn. Later varieties such as 'Claret', if planted out in late July or August, should come into production the following April.

If cauliflower, as Mark Twain wrote, 'is nothing but cabbage with a college education', then calabrese and broccoli have the PhDs of the family. The names are Italian but it seems that the broccolis came into Italy originally from the Eastern Mediterranean, some time during the 17th century. Philip Miller, who wrote one of the first gardening dictionaries in 1724, called it 'Italian asparagus'. It is certainly easier to grow broccoli than cauliflower, and useful to grow the purple sprouting kind of broccoli, rather than the chunkier calabrese. Every supermarket can give you calabrese, yellowing with age under its shrinkwrapped plastic. Purple sprouting isn't such an easy product for them to handle. It wilts quickly and its season is too short to be interesting to them. But broccoli has become one of a succession of newly hyped superfoods: high in the phytochemicals which are said to reduce the risk of cancer, high in vitamins A, C and E.

'Romanesco' (Marshalls £2.75) is by far the most beautiful of the calabrese, though I was never very successful at growing it. It makes a gorgeous lime-green head with domed curds arranged in a curious spiral, unlike any other member of its family. You sow seed in early May to get heads to eat in early winter.

The usual advice with brassicas is to sow seed thinly in drills from April onwards and transplant the seedlings to their permanent positions in early summer. The problem is that the transplanting gives them a shock, however much earth you try to dig up with the roots. Hot weather at this time doesn't help.

This was perhaps why my 'Romanesco' was never successful, shooting up into spindly, premature heads, instead of swelling into the kind of beauty shown on the seed packet. A better technique, if you want to grow from seed, is to set two or three seeds 'at stations' along a row, spacing the little clusters at six-inch intervals. First, pull out the weaker seedlings of each group and leave the boss plant to grow on in situ, without any need to transplant. Then thin these seedlings to about two feet apart in the row.

Seed offers more options to the gardener than buying in young plants, which are never available in as many different varieties. When you are choosing, look for the Royal Horticultural Society's Award of Garden Merit. This means that the vegetable has been grown in long-term trials at the Society's Wisley garden and has come through with flying colours. The purple sprouting broccoli 'Bordeaux' (Marshalls can supply a packet of seed at £1.95 as well as young plants at £4.25 for 16) has the AGM. So does 'Red Arrow' (Mr Fothergill £1.70), which is brilliant in stir fries.

I've never gone in for cabbages in a big way, but for their looks as well as their taste, I like red cabbages such as 'Red Flare', which is usually ready to cut from October onwards. Marshalls can supply plants (£4.45 for 16) which they send out from mid-May. If you are gardening in a small space, try 'Ruby Perfection' (Marshalls £1.95), which makes neat, solid heads with few outer leaves. Consequently, you can set the plants closer together than usual. Both will stand a long time in the ground without deteriorating.

Though starter plants are a more expensive option than seed, there are good reasons for growing brassicas this way. Grown from seed, they tie up ground for a very long time, 44 weeks from sowing to harvest. There is less reason to buy vegetables such as sweetcorn as plants rather than seed. Sweetcorn germinates fast, grows fast and the plants do not seem to attract the attention of so many predators as members of the cabbage family. If you start with plants of broccoli or calabrese, you've cut out a couple of dangerous months when birds, caterpillars, slugs and snails will all be intent on helping themselves rather than you.

All the brassica family like good, rich ground. Don't stint on the muck, the compost, or whatever other bulky manure you can give them. Mulch the ground around them as they grow to retain moisture. If you intend to grow brassicas regularly, remember to shift your growing ground each year, to prevent the buildup of diseases such as club root. Being nitrogen gobblers, they do well on ground where you might previously have been growing peas and beans. On windy, exposed sites, broccoli plants may need staking. They grow up to a metre. S E Marshall & Co, Alconbury Hill, Huntingdon, Cambs PE28 4HY, 01480 443390, www.marshalls-seeds.co.uk; Mr Fothergill's Seeds, Kentford, Suffolk CB8 7QB, 0845 1662511, website: www.mr-fothergills.co.uk