The fennel that grows as a weed on roadsides and anywhere else it can get a toehold is common fennel (Foeniculum vulgare). Bronze fennel, a more subdued variety, grown mainly for its ornamental, bronze-purple foliage is F. vulgare ‘Purpureum’, while Florence fennel (also called bulb fennel or finocchio) is F. vulgare var. azoricum. While the young stems, leaves and seeds of all three varieties can be used in cooking it is only the last variety that produces a bulbous base.
To avoid root disturbance (which can also cause plants to bolt), sow seed directly into the garden. Seed should be sown at a depth of 1cm and thinned to at least 25cm apart, in rows spaced around 50cm apart. If using plants from punnets, make sure they are not root bound, water them well before and after transplant, and handle them carefully. Choose a position in full sun, with rich, well-drained soil and apply lime prior to planting as Florence fennel grows best in an alkaline soil. Don’t be tempted to fill in the space between small seedlings with a quick-growing crop, as you would with brassicas, because fennel is allelopathic, which means it inhibits the growth of other plants around it. For the same reason, leave at least a 50cm gap between your fennel and other vegetables.
At around six weeks, when the base of the plants start to swell, begin to mound up the soil around them. This keeps the bulbs white and tender, and prevents the plants from toppling over.
The bulbs will be ready for harvest in around 100 days. Cut them before they reach 12cm or so in diameter and before the plants start to flower to avoid the bulbs becoming tough and woody, and losing flavour. If you slice the bulb off a bit above the ground new ones will grow from side shoots.
Once you have your bulbs there are many versatile ways to use them. Liquorice lovers can snack straight on the fresh bulb, but those less keen on the strong taste, which has quite a kick to it, can cook the bulb to reduce its liquorice flavour to a mild hint. Roasted in the oven or braised in an orange sauce, Florence fennel makes an ideal accompaniment for pork. Sliced thinly and added to salad or shaved with a vegetable peeler and served on top of fish it enhances the other flavours rather than overwhelms them.
One of fennel’s health benefits is to aid digestion. Chewing the seeds after a heavy meal can reduce indigestion and flatulence – and it sweetens the breath after eating curry or garlic.
To collect seed you will have to sacrifice the bulbs and leave a couple of your plants to flower and set seed. To harvest, cut the stems as soon as the seeds begin to turn brown. Pack the seed heads loosely into a paper bag with air holes poked around the top and place it in a warm, dry area for up to two weeks. Some of the seeds will fall off themselves and the rest can be picked off. Sieve the seeds to remove the chaff, then further dry them for storage by laying them on a tray in a warm, airy place for a few days or placing them in the oven on a low temperature for half an hour. Only use your own seed to grow further plants if there are no different varieties of fennel in the area (including different strains of Florence fennel) because they will cross-pollinate, and don’t use seed from any that have bolted as the trait can be passed on.