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​How to Grow ​​​​Fennel

​Fennel is a perennial, pleasant-smelling herb with yellow flowers. It is native to the Mediterranean, but is now found throughout the world. Dried fennel seeds are often used in cooking as an anise-like spice. Fennel's dried ripe seeds and oil are used to make medicine.


GROWING GUIDE

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Growing Notes

  • Plant fennel in spring after the last frost. It’s a great option for growing in raised garden beds, containers, and in-ground gardens.
  • Space fennel plants 4 to 12 inches apart, depending on the variety. Grow them in an area that gets at least 6 hours of sun and has fertile, well-drained soil.
  • Sow seed indoors 6 to 8 weeks before the last frost. Sow fennel in Plant fennel in well-drained compost-rich soil. The best is to sow each seed in individual pots. If there is no possibility, plant the seeds approximately ten inches (25 cm) apart and cover them with a light layer of soil, about 1⁄8 inch (0.3 cm) deep. It’s probably a good idea to plant a few more seeds than you need, then thin them out later.

SEEDS

START

Direct

GERMINATION

7-14 days

SEED LIFE

2 years

PLANTING

SOIL

Well-drained 

SUNLIGHT

Full Sun

SEEDS

12" apart

SEEDLINGS

6"-12" apart

DAYS OF HARVEST

80-90 days

Maintaining

Fennel benefits from rich, well-drained soil, with a pH of 5.5-6.8. Plant in a sunny spot for best results. Bear in mind that fennel is a Mediterranean crop, a cool-weather short-lived perennial, normally grown as an annual. Fennel survives light frosts, but will only survive over winter outdoors (assuming you didn’t harvest the bulb) in zones 6-10. In zones 2-5, it grows as a biennial. It tolerates some heat and cold but does best when it reaches maturity in cool weather. Depending on your climate, the seed may be sown in early spring, mid-spring, late summer, and early fall. Fennel grown for bulbs will not provide seed too – to get succulent bulbs, grow the plant fast, harvest before flower stems form, and provide plenty of water. If water is in short supply, put bulb fennel at the top of your watering list.


To germinate fennel successfully, the seeds must be in the dark, with a soil temperature of 60-90 °F. (70 °F is ideal.) Direct seed at 10 seeds/ft, in rows 18" apart. Thin the seedlings to 6-12" apart. Or station sow the seed, dropping three seeds together at 12” intervals along the row, later thinning to leave the strongest seedling at each station. If the soil is dry when you are sowing, soak the furrow first. Cover the seeds with 1/8-1/2” of soil. They will take about 7-10 days to emerge. To improve germination, try soaking and pre-sprouting the seed for several days.


Rich, well-drained soil, regularly irrigated, and cool temperatures produce top-quality bulbs. Plants grow best, and the flavors are superior when daytime air temperatures are 60-70 °F. Start to blanch the lower stems when the bulb is the size of an egg by hilling up soil around the bulb. Mulching (with organic materials such as straw or hay) can be a good strategy to trap soil moisture and cooler temperatures in spring – the bulbs will be sweeter and more tender. Clip off any seed stalks that start to grow. The bulbs will be ready about three weeks after reaching egg size.


​HARVESTING GUIDE

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The bulbs are harvested when they get to small tennis ball size. If you leave them to grow larger, the plants will probably bolt and the flavor of the bulbs will quickly become bitter. Use a sharp knife or pruners to cut the bulb free just above the taproot, right at the soil line. Trim the leaf stems about 1-2" above the bulb to prepare it for sale or storage. Bulb fennel requires 80-115 frost-free days to reach harvest.

Bulb fennel will keep in the refrigerator for up to 1 week or in a cold, moist place for 2 to 3 months. The best storage conditions are 32 °F with 95% relative humidity. Stalks can be dried or frozen; leaves can be frozen or dried as herbs. Dried leaves should be stored in an airtight container.

Saving Seeds

Allow the seed heads to ripen completely on the plan. When they become brown and dry, cut the heads and place in a brown paper bag or open jar to dry.

Collect seeds: Once seed heads are dry and the seeds have darkened, seal the paper bag or container and shake to release the seed.

Label and store seed in a cool, dry location. Fennel seeds can last up to three years.

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