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How to Grow Fennel’s Savory Seeds and Bodacious Bulbs

  • Bob Styer
  • Herbs
Fennel Bulbs In A Brown Wicker Basket.

So many herbs are native to the Mediterranean area, and this is another one.  People have known how to grow fennel for centuries, and The Bible even mentions it.  All the fennel we cultivate today comes from wild fennel, an invasive species in some areas.

Consider growing fennel in pots for an excellent addition to your container garden.  It also makes a great decorative plant.

Continue reading to learn about growing fennel bulbs from seeds and how to harvest fennel plants, bulbs, seeds, and even fennel pollen. We’ll also discuss some differences between the types of fennel.

Fennel flowers in a field in midsummer.
The yellow flowers of fennel in midsummer

How is Fennel Used?

This herb is a member of the parsley family.  You can enjoy raw fennel or roast it as a side dish.  It can also be a replacement for celery in soups and stews.  Fennel also makes a great addition to seafood, meats, and chicken.

Known for its anise flavor, fennel becomes sweeter and mellower when cooked.  All parts, including the seeds, are edible.  Besides being a popular herb and spice, it also has well-known benefits for digestion.

Are There Any Differences Between Anise, Fennel, and Licorice?

Although fennel, anise, and licorice have similar flavors, there are some differences.  Anise seeds have a sweeter but more robust flavor than fennel seeds.  Many people who don’t like licorice or anise prefer fennel since it’s less sweet and milder.  The flavor of licorice can be salty, bitter, or sour.

Gardeners only grow anise for its seeds, but you can eat all parts of the fennel plant.  Licorice has to grow for 3 – 5 years before the root is ready for harvest.  During that time, the root can grow up to four feet long.

Anise, fennel, and licorice flavors come from anethole essential oil.  Licorice root makes real licorice candy, but anise seeds are often a substitute.  An advantage of licorice root is that it imparts a natural black color to the candy.

A fresh fennel bulb cut in half with a wooden spoon full of seeds.
A fresh fennel bulb cut in half with a spoonful of aromatic fennel seeds

Types of Fennel

Although all parts of the fennel plant are edible, the three main varieties of fennel have favorite parts for use.  That puts the three types into two groups, herb fennel and vegetable fennel:

Herb Fennel

Gardeners grow herb fennels for their seeds, but the whole plant is edible.  They either grow a small bulb or no bulb.

Common Fennel (Foeniculum vulgare vulgare)

This perennial is the parent plant of all other varieties of fennel.  Also known as wild or bitter fennel, it can grow up to six feet high.

All parts of this plant are edible, but it has a small bulb.  The seeds have a more pungent taste and aroma than the cultivated varieties.

Sweet Fennel (Foeniculum vulgare dulce)

This type also goes by the names spicy fennel and Roman fennel.  An annual, it flowers and produces seeds in the first year.

Since this type flowers so quickly, it doesn’t make a bulb.  The seeds have a sweet aroma and are the most popular part of this type.

Vegetable Fennel

Florence Fennel (Foeniculum vulgare azoricum)

Finocchio or bulb fennel are two other names for this variety.  The bulb is the favorite part of this type, so gardeners grow it annually.

This plant will produce seeds in the second year. Store some bulbs over the winter and replant them next spring to harvest seeds in the fall.

All three types of fennel can cross-pollinate, so it’s best to grow one kind at a time.  Sweet and Florence fennels each have several subtypes with different characteristics.

Cantino is a bolt-resistant variety of Florence fennel that’s a good candidate for early planting.

The perennial fennel varieties are more “semi-perennial” since they need replanting after three or four years.

Another type is “giant fennel” (Ferula communis).  This plant is large and looks rougher than the other types.  It has a pungent aroma but isn’t edible.

Would you like to learn about other herbs? Check out our post “The Complete Guides to Growing Culinary Herbs” for links to those articles.

Substitutes for Fennel Bulbs or Seeds

When cooking, nothing beats having the exact herbs and flavorings you need.  Fennel, though, is one of those herbs that isn’t always available.  As a result, many people ask what they can use to substitute for fennel bulbs or seeds.

We divided this list into acceptable substitutes for fennel flavor and texture.  Of course, none is an exact match since every herb is unique. Let your imagination run and see which combinations you like:

Fennel Flavor Substitutes

  •  Anise seeds
  • Celery seeds
  • Parsley.  When cooked, fennel turns soft and has a mild flavor.  That’s what makes parsley a good flavor substitute.
  • Cumin
  • Licorice root
  • Caraway seeds
  • Dill seeds.  They have a similar texture to fennel seeds but a milder taste.

Fennel Bulb Texture Substitutes

Preparing the Soil

Fennel prefers well-draining soil that’s loamy and moist.  Mix one inch of organic matter, like compost, to a soil depth of six inches to prepare the soil.

Don’t add fertilizer while the fennel grows because well-fed fennel becomes less flavorful.  It prefers soil in a pH range from 6.5 – 8 with full sun.  Fennel grows well in Zones 6 – 10.

More information about soil and compost is in our articles “Testing Garden Soil and How to Make Improvements” and “How to Make Compost at Home.”

Fennel Seeds to Help You Get Started

Sow Right Seeds - Florence Fennel Seed for Planting - Non-GMO Heirloom Packet with Instructions to Plant and Grow in Your Herbal Garden - Great for Seasoning and Cooking - Attract Pollinators (1)
Sow Right Seeds - Florence Fennel Seed for Planting - Non-GMO Heirloom Packet with Instructions to Plant and Grow in Your Herbal Garden - Great for Seasoning and Cooking - Attract Pollinators (1)
$5.59
Buy on Amazon
2024-07-18
Fennel- Wild Italian Herb Seeds- Heirloom Variety- 100+ Seeds
Fennel- Wild Italian Herb Seeds- Heirloom Variety- 100+ Seeds
Price not available
Buy on Amazon
2024-07-18
Plant Good Seed Organic Bronze Fennel Seeds - Pack of 100, Heirloom Seeds for Planting Herbs - Gardening Supplies, Vegetable, Flower, Herb Garden - Non-GMO, Open Pollinated, from USA
Plant Good Seed Organic Bronze Fennel Seeds - Pack of 100, Heirloom Seeds for Planting Herbs - Gardening Supplies, Vegetable, Flower, Herb Garden - Non-GMO, Open Pollinated, from USA
Price not available
Buy on Amazon
2024-07-18
David's Garden Seeds Fennel Fino 25 Non-GMO, Heirloom Seeds
David's Garden Seeds Fennel Fino 25 Non-GMO, Heirloom Seeds
$4.95
Buy on Amazon
2024-07-18
Burpee Orion Hybrid Fennel Seeds 100 seeds
Burpee Orion Hybrid Fennel Seeds 100 seeds
$7.69
Buy on Amazon
2024-07-18

Growing Fennel from Seed

The best times to grow fennel from seeds are after the last spring frost date or early to mid-summer.  Start by soaking the seeds in water for 24 hours to help with germination.

Next, sow seeds ¼ inch deep and 4 – 6 inches apart in an area with full sun for 6 – 8 hours daily.  Water the seeds by spraying them with a spray bottle.  Once the shoots appear in 1 – 2 weeks, water them often.

Fennel isn’t a good candidate for transplanting since this is another herb with a long tap root.  If you buy plants or want to start seeds early, ensure they’re in peat pots.  That allows them to go right into the ground without root disturbance.

Caring for Fennel During the Growing Season

Fennel is easy to care for and usually only needs watering during the summer.  You could add grass clippings or straw around the plants to keep the weeds down and hold moisture.

Herb fennel is more drought-resistant than Florence fennel.  If Florence fennel grows in dry conditions, it will bloom, ruining the bulb’s flavor.  Keep it moist to prevent this.

Since herb fennel grows so tall, it might need staking to protect the stems from collapsing in the wind.  Florence fennel can develop bulbs above ground, so cover them with soil to protect them from the sun.

Pots for Growing Fennel

The HC Companies 16 Inch Sedona Round Self Watering Planter - Decorative Lightweight Plastic Plant Pot for Indoor Outdoor Plants Flowers Herbs, Cottage Stone
The HC Companies 16 Inch Sedona Round Self Watering Planter - Decorative Lightweight Plastic Plant Pot for Indoor Outdoor Plants Flowers Herbs, Cottage Stone
$31.99
Buy on Amazon
2024-07-18
Classic Home and Garden Honeysuckle Resin Flower Pot Planter, Blue Jean, 15'
Classic Home and Garden Honeysuckle Resin Flower Pot Planter, Blue Jean, 15"
$28.43
Buy on Amazon
2024-07-18
The HC Companies 17 Inch Round Classic Planter - Plastic Plant Pot for Indoor Outdoor Plants Flowers Herbs, Seafoam
The HC Companies 17 Inch Round Classic Planter - Plastic Plant Pot for Indoor Outdoor Plants Flowers Herbs, Seafoam
Price not available
Buy on Amazon
2024-07-18

Growing Fennel in Pots

Since it has a large taproot, fennel must grow in containers at least 12 inches deep.  The bigger, the better.  A 12-inch diameter pot that’s 12 inches deep will only hold one plant.

Fill the pots with organic potting mix mixed with organic compost.  The compost should be about 25% of the total blend.  If you’re feeling lucky, sow one seed in the center of the pot ¼-inch deep.

To improve the odds of germination, it’s better to sow two or three seeds near the center of the pot.  If more than one plant sprouts, thin out the weaker fennel seedlings.  Move the pots outside when the last spring frost is over.

Ensure you don’t uproot any plants you want to keep.  Fennel has a low tolerance for disturbing the roots.

Keep the soil moist.  Once the fronds have spread, snip them off and use them for cooking or salads.  When growing bulb fennel, mound soil around the bulb to protect it from sunlight.

Our article “Growing Vegetables in Containers” has more information about potting plants.

Fennel bulbs growing in a pot.
Fennel bulbs growing in a pot

Fennel Harvesting

The leaves of fennel (called fronds) and stalks are ready to harvest in about 90 days.  Only take a few fronds at a time to avoid harm to the plant.  The best time to start harvesting the bulbs is when they’re at least the size of a tennis ball.  When the plant flowers, the bulbs won’t be delicious anymore.

New shoots can sprout after cutting the bulb from the root.  For the best flavor, eat the shoots while they’re still small.

Other tasty parts of fennel include the yellow flowers and flower pollen.  When the heads are in full bloom, remove them and shake the pollen into a bowl.  After that, air-dry the heads and rub the florets to release more pollen.

You’ll have to remove the tiny stems that fall off and store the pollen in jars.  When we wrote this post, we checked the price of fennel pollen. A bottle weighing 0.5 oz. had a cost of $11.50.

A ten-pound bag of it sells for $1,711.00.  Definitely a spice with a high price tag!

Use fennel pollen in salad dressings or when cooking meats and vegetables. Cut off the flower heads and dry them for a few days.  Then squeeze four or five heads into a six-ounce jar and cover them with olive oil.  After a week, use the infused olive oil in salads.  The oil is also flavorful when sautéing or grilling meats and vegetables.

Harvesting Fennel Seeds

Once the seed heads turn brown, cut them off and lay them on trays to dry out.  Another option is to put the seed heads into brown paper bags.  When they’re dry and crunchy, shake out the seeds.  This is easy to do when the seed heads are bone-dry.

If you leave seed heads on some plants, the fennel will self-seed and sprout new plants next spring.  That saves the time needed for planting, but thin the new sprouts so they don’t choke each other.

Protecting Herb Fennel Over the Winter

Prune any remaining stalks, leaving two inches or so at ground level.  Root damage is possible during long winter freezes.  Add a three-inch mulch of straw, shredded leaves, or pine boughs to protect them.  Remove the mulch after the last spring frost.

Protecting Florence Fennel Over the Winter

Usually, people harvest all the bulbs, so this fennel doesn’t have to survive winter often. You can prepare them for winter if you miss some bulbs or want to harvest seeds next year.

Since Florence fennel has a large bulb, it needs a slightly different treatment than herb fennel.  Prune the stalks so they’re a few inches long, and heap soil around the bulbs to cover them.  Spread a three-inch layer of mulch over the covered bulbs for more protection.  Remove the mulch after the last spring frost.

Another method to overwinter Florence fennel takes more work.  Choose several healthy bulbs and cut back the fronds so they’re about 8 inches long.  Next, dig out the bulbs and plant them in pots.

Please remember that these plants have a long taproot, so dig deep enough to get it. Since the plants are dormant, there’s less chance of shocking the roots.

Store the replanted bulbs in a cool, dry place.  When stored over the winter, excessive water or humidity could cause fungal diseases on these bulbs.  Keep them dry and water them a few times to prevent this while in storage.

You can replant the bulbs outside after the last spring frost or leave them in the pots.  These bulbs tend to flower quickly, and their seeds will be ready to harvest in the fall.

Storing Fresh Fennel

Put whole fennel bulbs (without the stalks) in an open zip-loc bag and store them in the refrigerator.  They will stay usable for 7 – 10 days.  Seal cut fennel bulbs in bags or containers and store them in the fridge for up to three days.

Fennel seeds will keep in glass jars for about four years.

Freezing Fennel

To store fresh fennel by freezing, rinse the stalks and fronds in cool water.  Next, remove the excess water and put them in freezer bags or containers.  They’ll keep for about six months.

Another freezing method is to chop the stalks and fronds into small pieces, then put them in ice cube trays.  Top off the trays with water and freeze them.  Once the cubes freeze, remove them and put them in sealable freezer bags.  They can stay in storage for 10 – 12 months.

Freeze bulbs by quartering them and then blanching them in boiling water for one minute.  Next, put the cut bulbs in ice water for one minute.

After this, dry the pieces and put them in sealable freezer bags.  Fennel bulbs will change their texture after freezing.  The storage time is 10 – 12 months.

How to Dry Fennel

Fresh fennel is the best form to use. Like many herbs, fennel loses some flavor and aroma after drying.  The most significant advantage of dried herbs is that they have the longest storage time.  Whole or powdered dried fennel will keep in air-tight containers for over a year.

If you collect fennel seeds from a fully-dried head, then the seeds are already dry.  Store them in air-tight containers for up to four years.

Air Drying

Remove the fronds from the stalks.  The stalks are still useful for cooking or drying in an oven.  Tie the fronds in loose bundles and hang them upside-down in a cool, dry, well-ventilated area.  Depending on the ventilation, they should be dry in a week.

Drying in a Dehydrator

Lay the fronds in a single layer on the dehydrator trays.  Follow the dehydrator instructions for drying herbs.  Drying time will take one to four hours.

Drying in an Oven

Dry fennel stalks in an oven by removing all the fronds.  The fronds can be air-dried or dried in a dehydrator, as described above.  Dry some stalks whole to use them as a bed for grilling fish.  The dried pieces will be easier to grind or use in cooking.

Cover a baking sheet with parchment paper and lay the stalks or pieces in a single layer.  Set the oven to its lowest temperature, which varies from 140o – 200o F, depending on the oven.

Dry the stalks/pieces for three hours, checking them at times to ensure they don’t scorch.  After this time, shut off the oven and let them continue drying overnight.

Fennel Companion Plants

Fennel has gotten a bad rap for not being a good companion plant.  Gardeners who grow fennel report it’s an excellent companion for most crops.  That’s because it’s a top-notch insect repellant.

It even attracts beneficial insects like tachinid flies, ladybugs, hoverflies, parasitic wasps, and syrphid flies.

Fennel is an excellent plant for attracting swallowtail butterflies. Although the caterpillars eat some of the leaves, growing a few extra plants to attract the swallowtail butterflies is worth it. Besides their beauty, they’re also excellent pollinators for many plants.

Dill and fennel can cross-pollinate and alter each other’s flavor. It isn’t a good mix either way.

Learn about more companion planting options with our comprehensive Companion Planting Chart.

Eastern Tiger Swallowtail Butterfly, colored with yellow and black wings and spots of blue and red.
Eastern Tiger Swallowtail Butterfly
Swallowtail Butterfly Caterpillar, colored in green and black stripes with yellow and red spots.
Swallowtail Butterfly Caterpillar

Fennel Pests

Aphids

If the problem isn’t widespread, remove the infested leaves and destroy them.  Knock off the aphids with a strong water spray.  Spray them with neem oil or organic insecticidal soap for a more serious treatment.

Armyworms

These larval beasts can eat the leaves so they look like skeletons.  The moths lay fuzzy white egg clusters on the leaves that hold 50 – 100 eggs.

If that isn’t bad enough, the moths can lay eggs 3 – 5 times yearly.  That’s an effective way to create an army of worms!  Birds, parasitic wasps, spiders, damsel bugs, assassin bugs, and lacewings all prey on armyworms.

You can also apply a bacteria called Bacillus thuringiensis.  This is available as a spray and attacks many types of worm and caterpillar pests.

Cutworms

These larval pests do their damage at night and hide in the soil or under plant debris during the day.  Cutworms chew through the stems of plants at the soil line.  Protect the stems by covering them with aluminum foil or plastic collars.

The collars should extend an inch below the soil line and three inches above the soil line.  Be careful not to damage the roots when placing the collars.

A more straightforward way is to spread diatomaceous earth around the plants.  This will cut the worms as they crawl around.

Root-knot nematode

These nematodes cause swellings on the roots up to an inch in diameter.  The plants fail to thrive and then turn yellow and wilt when the weather is hot.  Treat the soil with neem cake to destroy these pests.

To learn more about organic pest control, see our article “Top 5 Natural Pest Control Methods You Can Use Now.”

Fennel Diseases

Neem cake is an effective fungicide that will prevent many fungal diseases.  Please check our article “All About Neem Oil and Neem Cake” for more information.  This article also has supporting references to scientific papers.

Root and crown rot

Healthy fennel roots are white.  This fungal infection turns the roots brown, and they’ll appear waterlogged.  The plant will wilt and suffer a slow or quick death.

To prevent spreading, pull up and destroy any infected plants.  Then, rotate the fennel out of that ground next year.  Replace it with an unaffected crop like corn.

A way to prevent this problem is to use fungicide-treated seeds.  Plant them in clean pots filled with sterile potting mix.

Botrytis

High humidity encourages this blight, and it attacks many herbs.  The plant has spots colored tan to brown caused by a gray mold.

Prevent botrytis by watering plants at the roots instead of overhead.  Water the plants in the morning so they have time to dry.  Botrytis can also appear if the plants are too close together.

Stem rot

This fungus attacks the stems, so they wilt and fall over.  The insides of the dead stems have small black bodies called sclerotia.  This is a soil fungus, so fight it by crop rotation.  Next year, plant corn or another plant immune to stem rot.

Damping off

This fungus affects the seedlings, so they either fail to sprout or die right after sprouting.  Many times, the seedling’s stem will wither at the base.

Use treated seeds, sterile potting mix, and clean pots to prevent this.  Destroy all seedlings because there’s a good chance they’re all infected.

Final Thoughts

Herbs never cease to amaze us.  The varieties of flavors, aromas, and flower colors are mind-boggling.  Besides that, there’s also the beneficial effects on our health.  If you haven’t tried fennel yet, it could be a welcome addition to your garden.

Last update on 2024-07-18 / Affiliate links / Images from Amazon Product Advertising API

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Bob Styer

As a child, I hated gardening. That was mainly because Dad expected us to work in the garden every so often even though we thought play was more important. Over the years, though, I've developed a real appreciation for growing things. Whether you're growing plants for food or to enjoy their beauty, gardening can make your life better. Seize the moment!

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