Fennel forms flowers in year two. They are also edible!
Foeniculum vulgare HARDINESS ZONE: Annual / Tender perennial 7-10 PLANT HEIGHT: 24-36" PLANT WIDTH: 10-12” SEED SPACING: 1-2" / Thin to 4-12" as they grow SEED DEPTH: 1/4-1/2" deep IDEAL TEMP: 65-70°F (18-21°C) GERMINATION: 7-14 days DAYS TO MATURITY: 50 - 60 SOIL: Moist, fertile, and well-drained LIGHT: Full Sun / Part Shade
In my experience, fennel is the most popular host plant for Swallowtail Butterflies. They prefer it over the other host plants in my garden by a wide margin.
PLANTING INFORMATION
Can be direct seeded (recommended) or started in containers for transplanting. Select a location with full sun and well-draining soil. Sow seeds ¼ inch deep when temps are mild. If planting in the fall, you’ll need to protect from frost and freezes. Seeds germinate in 7-14 days at 65-70°F (18-21°C). Eventually thin seedlings to 5-12 inches apart as they grow. Water regularly, maintaining consistent soil moisture without overwatering. Harvest leaves and stems before flowering for best flavor. For seed production, allow plants to flower in their second year. Plants may produce seeds the first year in areas with a long cool spring. Harvest seeds as they begin to turn their characteristic grayish-green color.
HARVEST INFORMATION
Leaves/Stems: Harvest before flowering for fresh use (check for baby Swallowtails!)
Flowers: Harvest florets for culinary garnishes
Seeds: Harvest in second year as they turn grayish-green
Roots: Can be harvested in fall of first year
Flavor Development: Mild at baby-leaf stage (young plants) Fuller, more intense at 8-12 inches tall
Note: Excessive moisture during bloom can prevent seed formation