Planting fennel by seed is the much easier option. Seed can be sown as soon as the soil warms in the spring. Soaking your seeds for a day or two before sowing will ensure better germination. Keep the area moist until the seeds sprout and thin the fennel plants to 12 to 18 inches apart when they are 4 to 6 inches tall. Plants will begin flowering about 90 days after planting.
When growing fennel, choose a sunny location in the back of a well-drained bed. The fine textured foliage can grow up to 6 feet tall and makes an excellent backdrop for another flower planting.
Fennel is a short-lived perennial that blooms best in the second year. It readily re-seeds and while not considered invasive, it has certainly earned its reputation for aggressive growing. Fennel can be cut back early in the season to encourage bushier growth and should be deadheaded for seed harvest and to prevent over seeding of new plants.
How to Plant the Herb Fennel
Choose a spot in your garden that has rich, well-drained soil and full sun. Improve your soil by working in 3 to 4 inches of compost or manure per square foot to a depth of 5 to 6 inches.
Prepare the area by raking the soil.
Sprinkle fennel seeds into the soil about 18 inches apart and cover with ¼ inch of soil.
Water the fennel until the soil is moist.
Harvest and dry seeds as the flower heads fade. There’s only one restriction to how to grow fennel: don’t plant it near dill. Cross pollination results in strangely flavored seeds for both plants!
Once established, fennel herb doesn’t need much care. It prefers acid soil, appreciates the occasional dose of mild fertilizer and a little additional water if the weather is hot and dry.
In addition to its kitchen contributions, planting fennel will attract beneficial insects to the garden and its leaves are a favorite with the caterpillars of the swallowtail butterfly.
Whether grown for its culinary value or strictly as on ornamental, growing fennel herb will be an easy and attractive addition to your garden.