How to Grow Fennel for Seeds

Find an empty 12-inch square area of your garden in a full sun exposure area during early summer. Fennel can be planted as early as after the last frost in the spring, but it tends to grow slowly in the cooler months. Most fennel seed is planted between the middle of May and the middle of June.

Loosen the top two inches of the soil with a rake or hoe. Water the loose soil with a garden hose until it is moist, but not saturated.

Drop a fennel seed into the center of the moist soil. Cover the seed with ¼-inch of loose soil. Loosely cover the entire fennel growing area with a loose layer of straw.

Water the fennel plant regularly once per week or when you notice the soil has dried out. Use garden vegetable fertilizer according to the manufacturer's directions once or twice during the growing season to increase plant size and seed harvest.

Harvest seeds about one month after the blooms appear. The old blooms wither and the grouping of seeds turns a green-grey color when mature and ready to be dried. Pinch the seed groups gently and transfer them to a paper bag.

Place the open paper full of harvest fennel seeds in a cool and dry location overnight. Roll the top of the bag closed and shake it vigorously from side to side. Dump the contents of bag into a bowl.

Return the ribbed oval-shaped fennel seeds to the paper bag and leave the other plant matter in the bowl.

Pour the bag of fennel seeds onto a framed screen and spread them into a single layer. Dry the screen of fennel seeds in a cool, dry and well-ventilated place for a week to 10 days. Move dried seeds to an air-tight container when they are crisp and not mushy when bitten into.