Fennel is one of those herbs that, even if you have absolutely no use for it in your kitchen, should be in the garden just because it’s so very, very pretty. It’s the softest of plants with its fine, feathery foliage. Even though it can grow quite large -three to five feet tall and as big around after a number of years- it’s not an imposing plant. Its ferny fronds move in the slightest breeze.
There are a couple of types of fennel grown. Common fennel, Foeniculum vulgare, is a perennial. It is the seeds and leaves of this plant that are used. Annual fennel, F. vulgare azoricum (Finocchio in Italy) gets enlarged lower stem parts called (improperly) bulbs that are eaten as vegetables. My favorite, the bronze fennel, has purple/brown stems and leaves rather than green and is a lovely plant and highly ornamental. It is a variety of the perennial type. All types have the same anise flavor in all parts.
All types of fennel take the same growing conditions- full sun and well drained soil. The perennial type is hardy to zone 5, but rarely makes a winter here because of the hard soil. I hope to one day get it amended enough that I can keep the bronze fennel going. Unlike many herbs, fennel does better with regular fertilizing to keep it from losing its color and vitality. It has a long tap root and resents being transplanted; if you start the seed indoors, make sure you plant it outside when it is still VERY small or its growth will be stunted. Fennel can be invasive in some areas; check with your extension agent to make sure it’s all right to grow in your county. I remember in San Diego in the late 1970s some of the canyons were just filled with fennel plants; a fair number of older Italians would go and gather it in summer. They were making good use of it, but it was still spreading faster than they could cut it. It spreads by seeds, not runners, so if you are conscientious about cutting the flowers off right after they fade and start to turn to seed, there will be no unwanted offspring.
If you are growing finocchio, watch the bottom of the plant. When it starts to swell up to about egg sized, pile dirt around it to keep sunlight off it. This will improve the flavor. You can use this bulb, and the stems, like celery, either raw or cooked. Perennial fennel will supply you with leaves for seasoning all season- you can start harvesting when the plant is only six inches tall, but only take the top two inches on this harvest. The seeds are excellent for cooking when harvested green, but wait until they are brown to dry and store them. Keep both types pruned back to keep them bushy, but if you want the yellow, dill-like flowers and the resulting seeds, do not cut the central stem. Fennel is a butterfly magnet- the flowers are visited by butterflies and bees, and certain Monarchs lay their eggs on the stems and the larva feed on them when they hatch. If you have a butterfly garden, you need fennel!
Fennel leaves are used to season fish and eggs and in German and Italian salads. The seeds are used in Italian sausage, rye bread, and in Chinese five-spice powder. In some parts of the world, they are chewed as a breath freshener. Fennel is also the ingredient that gives absinth its characteristic taste. It’s a versatile herb of many uses.