I have tried to grow fennel and cannot get it to bulb. I’ve tried growing it in several different locations, and I only get stems and tops. Do you have any suggestions?
You probably know that there are two kinds of fennel. Common or bronze fennel (Foeniculum
vulgare), which is 3-5 feet tall with a tough stalk and looks a
bit like dill, does not form bulbs. It is also listed as a non-regulated noxious weed in King County. The one you need is Florence, or bulbing, fennel Foeniculum vulgare
v. azoricum, which is less than 2 feet high with a white stalk that thickens
at the bottom to form a bulb-shaped vegetable.
Assuming you are planting the Florence fennel type, here is some basic information about growing it: it needs full sun and moderate water. According to Vegetables, Herbs, and Fruit by Matthew Biggs et al., it should be planted in the ground half an inch deep in late spring to late summer. It needs warm weather and will bolt (not form much bulb and get spindly) if the weather is too cold, too dry, or if it gets
transplanted. “Plants need a sunny, warm, sheltered position and well-drained, moisture-retentive, slightly alkaline soil. A light, sandy soil with well-rotted organic matter dug in the winter before planting is ideal. Stony soils and heavy clays should be avoided. Never allow the soil to dry out: mulch in spring and hand weed around bulbs to avoid damage. When the stem bases start to swell, earth up to half their height to blanch and sweeten the bulbs.”