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How to Grow Common or Sweet Fennel

Learn how to grow fennel in minutes. Fennel can be grown for its leaves, stems, flowers, and seeds. Common fennel is grown as an herb. Its leaves and seeds are used in cooking and baking. Florence fennel—which has a bulbous stem and is a variety of common fennel– is grown for its stem which is eaten as a vegetable. The leaves of common fennel are feathery with a licorice-like flavor. They can be added raw to salads and vegetables. The seeds of common fennel are often added to stuffing and apple pie.

How to grow fennel: fennel plants in the gardenGet to Know Fennel

  • Botanical name and family: Foeniculum vulgare (common fennel); Florence fennel is a cultivar of common fennel; it forms a bulb at the base of the stem; the botanical name of Florence fennel is Foeniculum vulgare azoricum.
  • Mediterranean
  • Type of plant: Fennel is an herbaceous perennial commonly grown as an annual.
  • Growing season: Summer
  • Growing zones: Zone 6 to 10
  • Hardiness: Fennel is heat tolerant but just slightly cold-tolerant; it will survive a frost but will die to the ground when freezing weather arrives.
  • Plant form and size: Fennel grows in clumps with numerous vertical stems from 5 to 7 feet tall; each stem branches near the top and each branch ends with a flat-topped cluster of small yellow flowers; fennel looks very much like dill but is taller and more coarse. Florence fennel is lower growing; it has a large thick stem or leaf base which is bulb-like. The bulb can be eaten as a vegetable and is often called finochio.
  • Flowers: Fennel has flat clusters of yellow flowers that grow in clusters or umbles at the ends of the stems above the foliage.
  • Bloom time: Fennel blooms from mid-summer to frost.
  • Leaves: Fennel has bright yellow-green leaves that are intricately divided, almost threadlike; they resemble dill leaves. Fennel leaves grow on upright, hollow, fleshy stems to about 5 feet tall.

How to Plant Fennel

  • Best location: Plant fennel in full sun.
  • Soil preparation: Plant fennel in well-drained compost-rich soil, however, fennel will grow in all types of soil. Fennel prefers a soil pH of 6.0 to 6.7.
  • Seed starting indoors: Fennel grows a taproot and is best sown in place. If started indoors, plant in individual peat pots so that taproots are not disturbed at transplanting. Sow seed indoors 6 to 8 weeks before the last frost.
  • Transplanting to the garden: Set fennel in the garden after the last frost in spring.
  • Outdoor planting time: Sow common fennel seed in spring as early as 2 to 3 weeks before the average last frost date. You can also sow fennel in late summer or early fall for harvest before the first frost. Fennel is half-hardy and will tolerate a light frost. Make succession plantings through late summer for harvest into autumn
  • Planting depth: Sow fennel seed ⅛ to ½ inch deep. Seeds must be covered completely to germinate.
  • Spacing: Space fennel plants 10 to 12 inches apart. Space rows 2 to 3 feet apart. Fennel re-seeds itself readily; plant it where it can grow for several seasons.
  • How much to plant: Grow 1 to 2 fennel plants for cooking; grow 4 to 5 plants for preserving.
  • Companion planting: Grow fennel with sunflowers, calendulas, and nasturtiums to attract butterflies, hummingbirds, and beneficial insects to the garden. Fennel is said to interfere with the growth of beans, tomatoes, and kohlrabi. Do not plant fennel near dill or cilantro; they may cross-pollinate.

How to grow fennel: fennel floweringHow to Grow Fennel

  • Watering: Give fennel regular, even watering until it is established. Once established, fennel can be kept on the dry side. Do not overwater fennel.
  • Feeding: Side dress fennel with aged compost at midseason.
  • Mulching: Mulch around fennel in summer to keep roots cool. To make bulb fennel tastier, mulch around the base of the plant to blanch the bulb and make it tender.
  • Care: Common fennel can grow 4 to 5 feet tall and may require staking or supports, especially if it is growing in a windy spot. Mound soil up around the base of Florence fennel to blanch the bulb and make it tender.
  • Container growing: Common fennel will grow easily in a container. Choose a container at least 12 inches deep; fennel forms a taproot so the container must be deep enough for the root.
  • Winter growing: Fennel can be grown outdoors in mild winter regions.

 Troubleshooting Fennel

  • Pests: Fennel is a member of the parsley family. Parsley caterpillars may attack fennel. Remove caterpillars by hand.
  • Diseases: Root rot can be a problem if fennel is overwatered or planted in soil that is not well-drained.

 How to Harvest Fennel

  • When to harvest: Fennel leaves can be snipped for fresh use once plants are 6 inches tall or more and established. Snip leaves before flowering. Common fennel will reach maturity in 60 to 70 days. Harvest the seeds of common fennel after flowering when they turn brown. The thick bulbs at the base of Florence fennel can be eaten like a vegetable as soon as it is large enough to eat; peak flavor of the bulb comes after flower buds have formed but before blossoms begin to open. Harvest seeds when they turn from yellowish-green to brown. If you do not want seeds, snip away flowers as they form.
  • How to harvest: Use snips or scissors to harvest leaves. Cut only the top 2 or 3 inches to ensure regrow.

How to grow fennel: fennel in the kitchenFennel in the Kitchen

  • Flavor and aroma: Fennel leaves and seeds have a pleasant licorice-like flavor.
  • Leaves: Use fresh leaves in salads and with vegetables, fish, pork, eggs, and rice. Young leaves are milder and sweeter than older fronds.
  • Stems: Fresh stalks can be eaten like celery. Use stems in salads or soups. They have a nutty
  • Bulbs: Harvest the bulb of Florence fennel while still tender, just before flowering. Eat it raw or cooked as a vegetable. Use bulb fennel in soups and pasta dishes. Slice the bulb thinly and add to salads. The bulb can be cooked in gratins, sautés, and casseroles.
  • Flowers: Fennel flowers are edible and can be added to salads.
  • Seeds: Use fennel seeds in home-baked bread, cakes, cookies, sausage, and beverages. Use seeds with cheese spreads, salad dressings.

Preserving and Storing Fennel

  • Refrigeration: Keep fresh fennel in a plastic bag in the refrigerator crisper; use fennel within three days.
  • Drying: To collect fennel seeds, cut the seed head and put it in a paper bag in a warm dry place; seeds will drop into the bag as they ripen and dry.
  • Freezing: Chop and freeze the leaves in a zippered bag for later use.
  • Storing: Dried leaves and seeds can be stored in an airtight jar.

Propagating Fennel

  • Seed: Grow fennel from seed that has been stratified (chilled or frozen) for at least 2 weeks. Direct sow seed in the garden any time of the growing season. Seeds sprout in 14 days.

Fennel Varieties to Grow

  • Florence fennel(Foeniculum vulgare azoricum), also called, finocchio, is grown primarily for its stems and bulbous base which can be used as a vegetable.
  • Bronze fennel( F. v. rubrum) has bronzy purple new growth that lightens to bronze in midsummer. Bronze fennel is grown as an herb and ornamental plant.

Also of interest:

How to Grow Florence Fennel

How to Grow Mint

How to Grow Thyme

How to Grow Oregano

How to Grow Parsley

How to Start a Herb Garden

Growing Herbs for Cooking




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  1. Ok, so I know when to harvest leaves and seeds. When do you harvest the bulb for cooking, and if I dig up the bulb do I then plant more seeds at that time?

  2. Florence fennel (Foeniculum vulgare var. azoricum) is the fennel grown commonly as an annual for its leaf base or bulb–there is a second variety (Foneniculum vulgare–or common fennel) commonly grown as a perennial for its seeds and young leaves. The flattened bulb of leaf-stalk base is ready for harvest 90 to 115 days after sowing–when the bulb is about 3 inches (7.5 cm) or more in diameter. You can cut the bulbous stalk just below the point where the individual stalks come together. You can use the leaves anytime after they have grown to about 18 inches long, but before they flower. As for sowing new seed: fennel requires a frost-free growing season and needs about 110 days to reach bulb harvest. If you live in a cold-winter climate you can start seed indoors 2 to 4 weeks before the last frost and transplant them out when the plant has about four leaves. If you live in a warm-winter climate: you can sow in spring for a summer crop or sow in late summer for a fall crop. A very warm regions, fennel will bolt in hot weather.

  3. You’ve put together a very informative article. I would like to correct one thing, the caterpillars you referred to as Parsley caterpillars are actually the caterpillars of the Black Swallowtail butterfly. The main reason I grow fennel is for the butterflies, as this, Italian parsley, dill, etc. are host plants for the Black Swallowtail caterpillars.
    Again, thank you for such an interesting and informative article.

    • Yes, correct. Parsley caterpillar is a common, not scientific, name for Papilio polyxenes, the larvae of the (eastern) black swallowtail, American swallowtail or parsnip swallowtail, a butterfly found throughout much of North America.

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