Growing fennel is relatively easy, as it is a hardy herb and can survive even after the first frost hits in the fall. In milder climates, growing fennel can be done year round. Because it grows to over 4 feet (1.2 meters) in height, it should be planted in the back of any herb, vegetable, or flower garden that includes other varieties of shorter plants. Tips for growing fennel include sowing the seed properly, creating optimal growing conditions, and keeping the flower heads pruned. The only minor caution with growing fennel is that it should not be started at a time where it will mature in hot temperatures, as this will make it go to seed more rapidly.
There are two main types of fennel. One is a vegetable annual that produces fennel bulbs similar to onions and goes by the name Finocchio or Florence Fennel. The herb fennel is a perennial that will come back every year and goes by the taxonomic name of Foeniculm vulgare azoricum. The herb variety does not develop an edible, bulbous root, but both varieties are otherwise very similar and require similar growing conditions. An easy way to tell the difference between the two when growing fennel is that herb fennel is purchased in seed form and Florence fennel is purchased as starter bulbs.
Starting herbal seed can be done by sowing it directly outdoors in the early spring or in pots indoors. Plant the seed 0.25 inch down (6.35 centimeters) and later space the seedlings about 1 foot (30.48 centimeters) apart. Additional plantings can be started in the middle of the season and harvested in late fall, as growing fennel is easy and it matures rapidly. The plant prefers full sun and moderately dry soil conditions. By removing flower heads as the plant begins to go to seed, it will continue to thrive and will likely survive several frosts as winter comes.
Florence Fennel bulb starters are more fragile than herb seed and should only be planted outside after the danger of all frost is past. The vegetable version requires the same growing conditions as the herb, which is well-drained soil and full sun, with an occasional fertilizer application throughout the season. The growing fennel bulbs can be harvested at any time whenever they reach a desired size. Though Florence Fennel is also frost-hardy, it is not as strong as the herb and will likely only survive one frost.
The bulbs and stalks of vegetable fennel have an anise or licorice-like flavor and are usually eaten raw like celery, or can go well with foods using tomato sauces and other vegetables. The leaves of the plant can be added to salads and also used to spice up sauces. The herb is often used to flavor soups, in fish dishes, and as a garnish. Herbal fennel is sometimes referred to as celery herb due to the similar uses for the two.