How To Grow And Care For Fennel

How To Grow And Care For Fennel
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Fennel, Foeniculum vulgare, is an aromatic Mediterranean herb in the Apiaceae (Umbellifer) family that includes carrots, celery, dill, and parsley. Lets look at How To Grow And Care For Fennel.

The rich, anise-like aroma and fragrance of the delicious yellow blooms, seeds, feathery leaves, pollen, roots, and stems, as well as their value as ingredients in traditional medicines and cooking, have long been prized.

The only species in the Foeniculum genus is vulgare.

There are many cultivated varieties and subspecies of it, including common fennel (F. vulgare ssp. vulgare) and Florence fennel (F. vulgare var. azoricum), which forms bulbs.

Because of its prodigious self-sowing abilities, F. vulgare has naturalized to the point where it is now invasive throughout California and the West.

If you cultivate the common variety, you can stop its spread by cutting off the flower heads before they set seed.

The Florence cultivar is less likely to self-sow since it is typically plucked before the blooms bud.

I’ll go over how to grow and harvest both common and Florence fennel in your garden in this article. Remember that we are giving you advice on how to grow and care for fennel before we get into propagation.


The best way to grow F. vulgare varieties is from seed.

Starting with a root cutting, or division of the crown, the region where the stems meet the roots, is feasible but difficult.

However, these plants are sensitive to disturbance and have long, thin taproots. Therefore, even though you might be able to take a cutting or make a division, the transplant might not work.

Fennel’s fruit and seed are identical, unlike several other fruiting plants, hence the terms are interchangeable.

Fennel seeds can be harvested from plants after the flowers fade, or purchased from quality purveyors. Remember our article is on How To Grow And Care For Fennel before I go into how to grow.

How to Grow

It’s recommended to plant fennel seeds indoors four to six weeks before to your area’s final date of frost if you want to grow it in the spring.

Do not forget that this is a cool-weather crop. It may bolt or go to seed if it becomes too hot or dry.

A close up vertical image of small fennel seedlings planted in garden soil with other leafy greens in soft focus in the background.

Using seed starting cells that disintegrate and transplanting them whole to the garden after the risk of frost has gone are also sensible choices because of the fickle taproot.

Alternatively, when the worst of the summer’s heat has passed, you can direct sow seeds into the garden in late summer or early fall.

Fennel and other herbaceous plants, especially those in the Apiaceae family, are known to not get along well. Avoid sowing it near together to prevent cross-pollination and flavor-damaging effects.

Pick a spot that gets direct sunlight. The soil should be a loose, biologically rich loam that drains well. The optimal soil pH is between 4.8 to 8.2, according to the Herb Society of America.

Conduct a soil test through your local agricultural extension office if you are unsure of the soil’s makeup or pH level in your garden. If necessary, amend the soil with compost or other rich organic matter, sand for improved drainage, and lime to neutralize highly acidic soil.

Work the dirt to a depth of about 12 inches, or until it is crumbly. As necessary, make adjustments.

Plant seeds in the ground 1/4 inch deep, then cover them with earth.

If you are mass planting, space the seeds four to six inches apart, with a walking distance of 12 to 18 inches between rows.

A close up horizontal image of human arms planting a row of seedlings in a herb garden in light sunshine.


During the germination and seedling phases, keep the soil damp.

Avoid moist soil, too, as it makes seedlings vulnerable to the fatal fungus “damping off,” which makes them fall over and die.

You can space seedlings 12 to 18 inches apart once they have two pairs of genuine leaves.

At this time, move indoor-started seeds to the garden. Before transferring them into the garden, give them a chance to acclimate to the outdoors by letting them stay in their seed starter pots for a day or two to harden off.

In order to prevent rotting, young plants should still receive regular irrigation, but avoid being overwatered or having water pool.

Although there may be times when more is necessary, an inch or two of rain per week, or equivalent watering, is typically sufficient.

Compared to ordinary forms, bulb variants are less resilient to dry conditions. Additionally, they are prone to “tip burn,” a condition wherein insufficient watering may prevent calcium uptake and result in the browning of the layer edges.


A close up vertical image of a mature Florence style finocchio fennel plant growing in a backyard vegetable garden.


Avert trouble with proper watering and harvest when the bulbs are young and about tennis ball sized, as opposed to older and larger.

You may fertilize Florence plants when the bulbs start to form.

Ken Adams and Dan Drost of the Utah University Extension recommend using three tablespoons of a 21-0-0 (NPK) fertilizer for every 10 feet of rows planted. Nitrogen is essential for the foliar development of F. vulgare varieties.

Do not apply fertilizer before plants are well established. Seedlings that receive too much nitrogen may be at increased risk for damping off.

Common F. vulgare blooms near the end of its growing season. If you don’t want it to drop seeds, you can cut the flowers off and remove them before they begin to fade.

In addition to its value as an edible, it provides an attractive, texturally-rich backdrop in the garden, particularly when it’s a bronze variety.

A vertical image of a mature fern-like fennel plant growing in a herb garden, with trees and perennial shrubs in the background..

When the vegetables first start to swell, mound soil or mulch up around the Florence types to keep the bulbs snowy white.

This method, known as “blanching,” protects against browning in the sun.

The Florence varieties’ bulb-like roots benefit from mulching so they stay white and are more satisfying to use in cooking.

A close up horizontal image of Florence type fennel bulbs covered with compost in a process known as blanching, pictured in light sunshine.

When bulbs are harvested young, at no more than four inches across, there may be no flower bud development at all.

If there is, you can snip the ends off the foliage to prevent bud formation, seed drop, and potentially invasive growth.

A close up horizontal image of rows of seedlings growing in planter trays pictured on a soft focus background.

You can also try growing fennel in containers on a patio or balcony. Two things to remember are:

  1. You’ll need a pot at least two feet deep to accommodate the long taproot.
  2. Pots dry out quickly, so be vigilant with watering.

Plants may need support in the garden as well as in containers. The required stability can be achieved using some rope and a few bamboo garden posts.

For a more compact shape, you can prune common F. vulgare by cutting it back by one-third in the early summer.

Be aware that planting for a fall crop in the middle to late summer may be preferable in regions where summer heats up quickly.

Plants have a tendency to “bolt,” or suddenly go to seed, during exceptionally warm spells, which might cause maturation to abruptly stop. Flowers and foliage might be salvageable, but immature bulbs will likely be a loss.

The garden should also be routinely weeded to lessen competition for water, ward off pests, and prevent moisture buildup that can result in disease, particularly fungal diseases.

Read also: Using Garlic As Pest Control In The Garden

Cultivars to Select

When selecting seeds, deal with reputable purveyors, and choose those that have been bred with exceptional qualities.

Here are several to consider:


This bronze cultivar makes a stunning accent to the herb garden even without the vegetables.

Enjoy the spring’s bronze foliage, which turns green during the growing season. As required, gather and prepare fresh herbs.

Yellow blossoms can be dried to extract the fragrant seeds, which make excellent garnishes.

A close up horizontal image of bronze fennel foliage tied with string isolated on a white background.


Plants mature in about 65 days at heights of approximately four feet.

Find bronze fennel seeds from True Leaf Market in a variety of packet sizes.


For crunchy bulbs that are zesty fresh as well as cooked, you can’t beat the Florence variety.

Plants top out at a towering 30 inches in 60 to 90 days.

A close up square image of the freshly harvested bulbs of Florence fennel set on a wooden surface.


Don’t forget to blanch the snowy bulbs with soil or mulch to keep them from browning in the sun.

Find packet of 400 Florence seeds available from Burpee.


At 24 inches tall, this hybrid is one of the more compact bulb varieties, appreciated for being less leggy than taller cultivars.


It’s been bred for outstanding tip-burn resistance, and won’t disappoint.

Plants mature in 80 to 85 days.

Managing Pests and Disease

Pest and disease problems should be at a minimum when you start with excellent seed, cultivate during cool weather, offer rich soil that drains well, don’t overwater, and maintain the garden clear of weeds.

Even yet, we occasionally have to deal with herbivores, insect pests, and diseases that are frequently carried by these pests.

Although deer and groundhogs don’t appear to be interested in its perfume, you may find that rabbits are rather interested in your plants.

Some pests to be aware of are:

  • Aphids
  • Slugs and snails
  • Swallowtail butterfly caterpillars, aka parsley worms
  • Thrips

A strong spray of water from the hose may be sufficient to get rid of sap-sucking aphids and thrips. Applying organic neem oil topically could be helpful in treating major infestations.

You can set traps for slugs and snails and then throw away any that are caught.

You could have conflicting emotions regarding the caterpillar of the swallowtail butterfly. It will probably eat the aphids, but it will also gorge itself on the greenery.

If you ultimately decide that you simply cannot share, try picking them off by hand or try putting in some yard decorations, such as a bird feeder or a warm birdbath, and letting avian guests help keep them in check.

In addition, there are a few diseases that may present themselves, including:

  • Cercospora leaf blight
  • Damping off
  • Downy mildew
  • Powdery mildew
  • Rust

We’ve already discussed damping off, a fungus that destroys seedlings and has no known treatment.

With the exception of downy mildew, which is brought on by a type of water mold called an oomycete, these ailments are mostly fungi.

All have an impact on the foliage, typically resulting in malformation and discoloration. Fungicides designed for edible plants are likely to have positive effects on them.

Given this possibility, I advise against following the suggestions of some gardeners who advise planting fennel next to rose bushes so the swallowtail caterpillars can consume the aphids that frequently wreak havoc on them.


You can pick the tender young shoots of common varieties to enjoy as tasty microgreens, while mature leaves are exceptional when chopped finely as a fresh herb.

A close up horizontal image of a mature fennel plant with small yellow flowers going to seed in a herb garden.

Even the stems can be used, like tough celery, in slow-cooked dishes.

To prevent shocking the plant into bolting or causing it to go to seed too soon, try not to harvest more than one-third of the entire plant at once.

The flowers can also be harvested to be used fresh or to be dried and the pollen, which has the strongest anise flavor of all, scraped off.

A close up horizontal image of the seed top of a mature Foeniculum vulgare plant pictured on a soft focus background..

Collect the seeds when they’re green, just after the pods form, or wait until the pods turn brown and the seeds are dry.

For Florence varieties, gather the bulbs when they are about the size of a tennis ball, or at most, four inches across.

A close up horizontal image of a trimmed and cleaned finocchio bulb set on a rustic wooden table.

Each should be cut off with a clean knife at the ground level, and the lengthy stems and abundance of leaves should be cut off three to six inches above the bulb. Any component may be utilized!

These plants are done when they are young and collected. There won’t be any seeds since there won’t be any flowers.

Allow some of the bulbs to grow larger if you’re growing this variety and want flowers and seeds; eventually, flower buds will form, blossom, and produce fruit.

If a hard freeze is forecast, harvest what you can quickly, including digging up the roots to use as you would carrots, if you’re so inclined. Plants may be able to tolerate a light frost.

Storing and Preserving

To store Florence fennel, cut the long stalks off, leaving about two inches above each bulb.

I like to slice the bulbs of Florence types in sections about an inch thick, and store them covered in water in an airtight container in the fridge.

Each morning I change the water and they last for up to five days, before turning brown and getting soft.

A close up horizontal image of two fennel bulbs set on a wooden surface with a small jar of seeds to the right of the frame.

Whole bulbs can also be kept in the refrigerator for three to five days, or up to a week and a half if you cover them with a damp paper towel.

Cut foliage is very sensitive and rapidly becomes limp. Consider using it the same day you choose it. By chopping the stalks and storing them in a water container until needed, you can keep it ready.

To use the feathery leaf in salads, as aromatic garnishes, or sprinkle it into savory cooked foods like you would dill, simply snip off the desired amount.

The stalks work best in prepared meals because they can be a touch rough. Some people dry them for two hours or so in a low oven set at 200°F.

They are a nutritious addition to slow-cooked soups and stews when they are fresh and store for up to two weeks in the refrigerator.

Within a week of being harvested, green fennel seeds should be stored in the refrigerator and eaten.

Pollen that has been scraped and collected from dried flowers keeps well for about two years in a sealed jar.

When kept in an airtight jar, dry seeds should last for several years while maintaining their robustness and aroma. Keep some on hand to chew as a digestive aid and breath refresher or to use as a spice.

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