Learn About Fennel

How to Sow

Sowing Seed Indoors:

  • Sow seeds indoors 4-6 weeks before the last frost in spring using a seed starting kit
  • Sow seeds ¼ inches deep in seed-starting formula
  • Keep the soil moist at 70 degrees F
  • Seedlings emerge in 7-14 days
  • As soon as seedlings emerge, provide plenty of light on a sunny windowsill or grow seedlings 3-4 inches beneath fluorescent plant lights turned on 16 hours per day, off for 8 hours at night. Raise the lights as the plants grow taller. Incandescent bulbs will not work for this process because they will get too hot. Most plants require a dark period to grow, do not leave lights on for 24 hours.
  • Seedlings do not need much fertilizer, feed when they are 3-4 weeks old using a starter solution (half strength of a complete indoor houseplant food) according to manufacturer’s directions.
  • If you are growing in small cells, you may need to transplant the seedlings to 3 or 4 inch pots when seedlings have at least 3 pairs of leaves before transplanting to the garden so they have enough room to develop strong roots.
  • Before planting in the garden, seedling plants need to be “hardened off”. Accustom young plants to outdoor conditions by moving them to a sheltered place outside for a week. Be sure to protect them from wind and hot sun at first. If frost threatens at night, cover or bring containers indoors, then take them out again in the morning. This hardening off process toughens the plant’s cell structure and reduces transplant shock and scalding.

Sowing Directly in the Garden:

  • Sow outdoors in spring after the last frost. In frost free areas sow from fall to early spring.
  • Sow in average soil in full sun.
  • Sow seeds thinly and cover with ¼ inch of fine soil.
  • Firm lightly and keep evenly moist.
  • Seedlings emerge in 7-14 days.

Planting in the Garden:

  • Select a location in full sun where water drains quickly after a rainfall.
  • Prepare the bed by turning the soil under to a depth of 8 inches. Level with a rake to remove clumps of grass and stones.
  • Dig a hole for each plant large enough to amply accommodate the root ball. 
  • Carefully remove the plant from its pot and gently loosen the root ball, if tight, with your hands to encourage good root development. 
  • Place the top of the root ball even with the level of the surrounding soil. Fill with soil to the top of the root ball. Press soil down firmly with your hand leaving a slight depression around the plant to hold water. 
  • Use the plant tag as a location marker. 
  • Water thoroughly, so that a puddle forms in the saucer you have created. This settles the plants in, drives out air pockets and results in good root-to-soil contact.
  • Do not allow plants to dry out, but never let the soil stay wet. 

How to Grow

  • Thin 10 inches apart when seedlings are 1-2 inches high.
  • Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their seeds from germinating. 
  • Mulches also help retain soil moisture and maintain even soil temperatures. For herbs, an organic mulch of aged bark or shredded leaves lends a natural look to the bed and will improve the soil as it breaks down in time.  Always keep mulches off a plant's stems to prevent possible rot.
  • Keep plants well-watered during the growing season, especially during dry spells. Plants need about 1 inch of rain per week during the growing season. It's best to water with a drip or trickle system that delivers water at low pressure at the soil level. If you water with overhead sprinklers, water early in the day so the foliage has time to dry off before evening, to minimize disease problems. Keep the soil moist but not saturated. 
  • As a tender perennial, sweet fennel is short-lived but will reseed abundantly.
  • Monitor for pests and diseases. Check with your local Cooperative Extension Service for pest controls recommended for your area.

Growing tips

  • Enjoy the young leaves as a garnish and flavoring for soups, salads, and fish.
  • Bulbous stems may be roasted, grilled or served raw.
  • Stalks may be used as a celery substitute or used to make broths.
  • Use the tasty seeds crushed or whole in sausage and other meats, as well as to make a refreshing tea with a warm, sweet anise flavor.
  • Fennel’s lacy texture makes it a valuable garden plant and it is also a favorite of black swallowtail butterfly caterpillars. 
  • Fennel may be stored fresh in a plastic bag in the crisper drawer in the fridge for a few days. Separate the stalks from the bulbs and store separately.
  • Fennel bulbs may also be frozen after blanching for three minutes.
  • Leaves may be dried, but lose flavor when dried. Stalks may be dried, but remove the leaves first.
  • Seeds are easily dried.

Common Pests and Problems

Common Disease Problems

Cercospora Leaf Blight: Small flecks which develop a yellowish halo appear on the leaves and turn brown and coalesce. They cause the leaves to wither and die. Burpee Recommends: Remove infected plants and destroy all plant debris. Rotate crops.

Damping Off: This is one of the most common problems when starting plants from seed. The seedling emerges and appears healthy; then it suddenly wilts and dies for no obvious reason. Damping off is caused by a fungus that is active when there is abundant moisture and soils and air temperatures are above 68 degrees F. Typically, this indicates that the soil is too wet or contains high amounts of nitrogen fertilizer. Burpee Recommends: Keep seedlings moist but do not overwater; avoid over-fertilizing your seedlings; thin out seedlings to avoid overcrowding; make sure the plants are getting good air circulation; if you plant in containers, thoroughly wash them in soapy water and rinse in a ten per cent bleach solution after use.

Downy Mildew: This fungus causes yellow spots on the upper surface of the leaves, and whitish gray patches on the undersides and eventually both sides of the leaves. Burpee Recommends: Rotate crops with plants in a different family. Avoid overhead watering. Provide adequate air circulation, do not overcrowd plants. Do not work around plants when they are wet.

Powdery Mildew: This is a fungus disease that causes a white powdery look on the foliage. This disease weakens plants as it inhibits their ability to make carbohydrates for themselves using sunlight. Burpee Recommends: You can remove infected plant areas, increase air circulation, and try to reduce the humidity in the room. Check with your Cooperative Extension Service for fungicide recommendations.

Rust: Lesions on the leaves are light green and become chlorotic. Yellow-orange pustules are seen on the underside of the leaves. Plants may become distorted.  Burpee Recommends: Check with your Cooperative Extension Service for fungicide recommendations.

Common Pest and Cultural Problems

Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.

Armyworm: Holes in leaves can be singular or clumped together. Leaves can become skeletonized. Egg clusters may be evident on foliage with a cottony or fuzzy appearance. Young larvae are pale green and adults are darker with a light line along the sideand pink underside. Burpee Recommends: Introduce natural enemies to the area.

Cutworms: These insects cut off the seedlings at the soil level. Burpee Recommends: Place a paper cup collar (use a coffee cut with the bottom cut out) around the base of the plant. They are usually mostly a problem with young seedlings. You can also control by handpicking and controlling weeds, where they lay their eggs.

Slugs: These pests leave large holes in the foliage or eat leaves entirely. They leave a slime trail, feed at night and are mostly a problem in damp weather. Burpee Recommends: Hand pick, at night if possible. You can try attracting the slugs to traps either using cornmeal or beer. For a beer trap, dig a hole in the ground and place a large cup or bowl into the hole; use something that has steep sides so that the slugs can’t crawl back out when they’re finished. Fill the bowl about ¾ of the way full with beer, and let it sit overnight. In the morning, the bowl should be full of drowned slugs that can be dumped out for the birds to eat. For a cornmeal trap, put a tablespoon or two of cornmeal in a jar and put it on its side near the plants. Slugs are attracted to the scent but they cannot digest it and it will kill them. You can also try placing a barrier around your plants of diatomaceous earth or even coffee grounds. They cannot crawl over these.

Whitefly:These are small white flying insects that often rise up in a cloud when plants are disturbed or brushed against. Burpee Recommends: They are difficult to control without chemicals. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for pesticide recommendations.


Should I eat fennel raw or cooked? Many parts of the fennel plant may be eaten, including bulb, stalks, leaves and seeds. You can cook the bulbs and stalks, use seeds in cooking and use the leaves in cooking. Leaves, stalks and bulbs may also be used raw.

Can I grow fennel in a container? Fennel can grow large, although ‘Orion’ is a smaller more compact variety. If growing fennel in a container use an 18-24 inch container and be sure to use a commercial potting mix rather than garden soil.

Can I use fennel as a companion plant? Fennel attracts beneficial insects to the garden. Otherwise is not is commonly used as a companion plant and may inhibit the growth of neighboring plants.

What do I do if I see caterpillars?? Fennel is a host plant to black swallowtail butterflies, so the caterpillars are a good thing in your garden.

I had fennel last year and it seems to be coming back, does fennel self sow? Yes, fennel is a short lived perennial plant and does tend to self sow where it is happy.

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