One of our favorite fall vegetables is fennel. Like many plants that are grown for leaves or stems, fennel will quickly bolt to seed in hot weather. It does OK in the spring and will get to a reasonable bulb size as long as you can get it to germinate early enough (late March in zone 5-6). It germinates best in very warm soil, so in the spring you need to find ways to warm up the soil as much as possible. One trick is to put a coating of pea gravel on top of the bed and sprinkle the seed in the gravel. The gravel holds heat and the crevices act as little ovens … which is why most herbs love to sprout in gravel where you don’t want them or in places like the cracks of your driveways or sidewalks. Anyhow … I digress.
Fennel is really best grown by starting it in mid July (again zone 5-6) with direct seeding. It needs to be carefully watered for good germination. I seed it into 6″ trenches which are spaced about 18″ apart. The trenches help with summer watering and this is important since fennel that is grown for bulbs needs, like celery, a LOT of water … especially in the heat of the summer. Right about now (early Sept.) I have good strong plants that are about 1′ in diameter at the base of the bulb. I thinned them when they first came up. I’ll soon thin them again within the rows so they stand about 9″ apart which means, in my case, removing every other one … the thinnings will be roasted with tomatoes, peppers, eggplants or some other summer produce and then served with oil, good vinegar and some shaved cheese.
When the bulbs get bigger at the end of the month or mid Oct., I’ll start to pull some additional soil over the trench to blanch the bulbs a bit more. As cold weather approaches, I’ll also mulch them to keep the bulbs from freezing while they are storing themselves right there in the garden. I should get bulbs that are in the vacinity of 4-5″ in diameter and have them most of the winter, especially if we get a snow covering.