Gardening: The growing pains of Florence Fennel

You need to be sensitive to nurture this plant. It will bolt when faced with anything it can't understand.

Florence fennel is a catwalk vegetable: it always looks good in photographs, is curvaceous, elegant - and temperamental. A letter from a reader suggests I'm not the only one that has had trouble with it. "I have been trying to grow Florentine fennel for two years without any success" writes Alison Davidge of Wantage. "I have bought the correct seeds (Johnsons) clearly marked Herb Fennel on the packet. I have sown them in small hollows 18in apart in April and then thinned them out to the strongest plant per group."

Ms Davidge goes on to say that her vegetable plot is in a sunny position and the soil rich and well drained, but although her plants have produced a great deal of green ferny growth, they have never thickened up to produce succulent white bulbs.

My guess is that Ms Davidge has not in fact got the right seed for the job. There are two sorts of fennel: one is classed as a herb, shoots up to about five feet and produces the leaves and seeds that are often used in fish recipes. Its proper name is Foeniculum vulgare. The fennel she wants is a different beast altogether, Foeniculum dulce, which, if you get the growing conditions right, swells at the base to produce a vegetable with a strong aniseed flavour, wonderful braised in a gratin with tomato and cheese.

She does say, in fact, that her seed packet is marked "Herb fennel". Johnsons does not list Florence fennel, at least in its 1996 catalogue. It is available from Unwins (pounds 1.35) or from Marshalls who call it sweet fennel (77p). The best varieties to look for are the ones that have been developed to resist early bolting. `Cantino' is good. So is `Zefa Fino' which is much better in cool climates than an authentic Italian strain such as `Di Firenze'.

The problem with Florence fennel, even when you have got the right seed strain, is that, like a highly bred horse, it still tends to bolt when faced with anything that it does not understand. In warm countries such as Italy, if it is well watered, it grows unchecked to produce a juicy, tender crop. In chillier conditions, it leaps up into flower before the base has swelled into anything even remotely edible.

Because Florence fennel is also sensitive to day length, the best time to sow is in mid June for an autumn crop. Early sowings (April-May) are more likely to bolt. The days are shorter then and there is more risk of a sudden chill. Either factor can make the fennel screech "Help!" and leap into flower. To perpetuate itself is the strongest urge in any plant. Taste and succulence are our priorities.

If you sow in mid June, you should be able to harvest bulbs by mid October. Fennel can stand light frost, but will not survive outside through any but the mildest winter. The best soil is light, sandy and well drained, but the bulbs must never be allowed to dry out. Put them top of the list if water is short.

You can sow seed "at stations" as Ms Davidge did, setting three seeds together at one foot intervals in a row and thinning the emerging seedlings to leave the strongest one growing at each station. Or you can dribble seed thinly along a drill and thin those. The second option is more wasteful. Thinning is much better than transplanting as fennel rarely recovers from the shock of being transplanted and so gives itself another good reason to bolt.

The bulbs must never be starved or thirsty. If the soil is dry when you are sowing seed, soak the drill first. Then keep the plants growing smoothly by watering and feeding well. Mulching round the plants helps to conserve moisture in the soil and also keeps down weeds. Fennel does not like competition. In September, start to earth up the bulbs. This keeps the plants stable and also blanches the folded, interleaved stems which make up the bulbs.

When you want to eat them, cut the bulbs just below ground level. The stumps may throw up some feathery-looking shoots which you can use as you do herb fennel. Although it is picky about growing conditions, fennel is not prone to pests and diseases. Chewing pests may be put off by its strong aniseed flavour.

Gardeners, too. Florence fennel has been known in England since the 18th century when the nurseryman, Stephen Switzer of Millbank, London, first included it in his seed list. He probably brought it in from Italy, where for centuries, gardeners had been selecting and reselecting from wild forms of fennel, to breed a strain with a bigger and more succulent bulb. But though fennel has been available here for more than two hundred years, it has never been a widely grown vegetable.

Unwins' catalogue has it listed in a special section of "Gourmet Vegetables" which includes globe artichoke, asparagus, aubergine, good King Henry, Hamburg parsley, kohl rabi, okra, pak choi, radicchio, pumpkin, squash and Swiss chard.

Kohl rabi provides a much quicker crop than Florence fennel. Seven or eight weeks after sowing, it should have produced a swollen stem about the size of a tennis ball. Don't leave it to get any bigger. Small is succulent. Kohl rabi is an odd looking thing, a cabbage that thinks it's a turnip, with a taste that is a mixture of both. Although it does not look like a cabbage, it is a full paid-up member of the brassica family.

As well as growing fast, kohl rabi is more tolerant of drought than other members of the cabbage family. It likes light, sandy soil, fertile and well-drained and is best sown outside in short drills, little and often, from April through to August. Thin out the plants as they develop, leaving them at a final spacing of 6-9in.

There are several different kinds, with white, green or purple skin. The purple ones are decorative, with the leaves sprouting round the swollen stem like some extraordinary head dress, but the pale kinds grow and mature faster than the dark-skinned cultivars. `Rowel' (Marshalls, pounds 1.49) is one of the best, with crisp-textured, juicy white flesh.

Flea beetle was a nightmare on brassicas last summer. The noise of them jumping off the cabbage leaves was even louder than the sound of my foot crushing the snails that were eating the lettuce. Because kohl rabi is one of the cabbage tribe, it gets attacked along with the rest. Plants at the seedling stage are most at risk. After that, comfort yourself with the thought that the swelling stem is your target, not the pepper-holed leaves.

S E Marshall & Co Ltd, Wisbech, Cambs PE13 2RF (01945 583407); Unwins Seeds Ltd, Histon, Cambridge CB4 4ZZ (01945 588522)