Florence fennel is a cool-weather perennial grown as an annual. Grow fennel in full sun. a wonderfully ornamental vegetable, is grown for its swollen leaf bases or ‘bulbs’ and edible leaves. When using in salads, the flavour can be improved by slicing the bulb and putting it in a bowl of water and ice cubes in the fridge for an hour. Plant fennel in well-drained soil rich in organic matter. Prepare the bed in advance by working in aged compost. Fennel prefers a soil pH of 5.5 to 6.8.