Unlike the commonly known Florence fennel, which produces a bulbous root, Common or Sweet fennel isn’t usually planted for its root; instead, it’s prized for its leaves and seeds, which have a flavor akin to anise. The feathery foliage grows 3–6′ tall and is often used as a garnish or herb. The flowers of this plant are bright yellow and very similar in appearance to the flowers of the dill plant. Seeds can be used as a spice, made into tea, or used to freshen breath. This variety of fennel is a fast grower and is, in many parts of the US, actually considered an invasive weed. For this reason, if you have limited space, planting in a pot is recommended as it can help keep your plant contained.
A word of caution if deciding to grow fennel in your garden. This plant should not be grown near other garden plants since it emits a chemical that can inhibit their growth. Now, that’s not very nice, but after tasting the sweet crunch of a fresh bulb, we’re sure you’ll find a way to forgive!
Seed Depth: 1/8–1/4″
Space Between Plants: 6–12″
Space Between Rows: 10″
Germination Soil Temperature: 45–90°F, while 70°F is ideal.
Days for Germination: 10–14
Sow Indoors: Sow inside 4–6 weeks before average last frost.
Sow Outdoors: 2–3 weeks before the average last frost date. For a continuous harvest, sow every 3 weeks until midsummer.
Vegetative: Fennel will grow well from seed but can also be propagated using root cuttings or crown division.
As fennel hails from the Mediterranean, it’ll do best in climates that mimic this region. Mild temperatures around 60–70°F and good air circulation will maximize your crops productivity, although it’ll still grow in temperatures that surpass this range—up to 90°F—as long as it’s provided with shade and adequate irrigation. Fennel can be grown as an annual in climates below USDA Zone 6 and, in warmer regions, can be grown year round as a perennial.
Natural: Full sun. Will tolerate partial shade in hot weather.
Artificial: Will grow well indoors under T5 fluorescent lamps or HIDs. Keep T5s 1′ above plants and HIDs 2–4′ above plants to avoid burning.
Soil: Prefers loamy, well-drained soil. A pH of between 5.5–7.5 will keep plants healthy and nourished.
Soilless: Germinate seeds in a soilless mix that drains well, such as those that contain perlite, vermiculite, or coco coir.
Hydroponics: Will thrive in a hydroponic media bed system; however, growing fennel hydroponically tends to take more time than growing fennel in soil.
Aeroponics: Will thrive in an aeroponic system.
Water: Requires moderate to high levels of water. In earlier stages of growth, plants should be watered regularly enough to keep soil moist, but make sure that soil is well-drained to avoid root rot. Once plants have become established, they can tolerate slightly dry soil.
Nutrients: Is a light feeder and does not require very rich soil. If soil is highly acidic, add limestone to neutralize.
Pruning: A hearty plant, fennel does not require a great deal of pruning to keep up its productivity. That said, plants that are grown as a perennial can be cut back by removing old or weak-looking branches in early spring to encourage new growth.
DEFICIENCY(S):This plant tends to be susceptible to tip burn, which is often caused by a calcium deficiency or lack of water. To remedy this problem, amend soil with limestone, eggshells, or gypsum and increase watering if natural precipitation is sparse.
Companions: Fennel’s chemical outputs make it a poor companion plant for any other plant species. Dill, as the exception to this rule, could be planted with fennel, but unwanted cross pollination might take place between the two. Keep fennel in its own space, downwind from other plants, or in its own container.
Harvest: Leaves and stems may be harvested as soon as they begin to mature by cutting off sprigs as needed, or the whole plant may be harvested by cutting the main stalk just above the soil surface. Seeds may be harvested once they turn grey/green. They may be harvested up until they turn dark brown but will likely fall to the ground before you are able to collect them, so be sure to keep an eye on the progress of your plant if you are planning to store seed.
Storage: Leaves are best used fresh but may also be dried. Leaves can be dried by bunching stalks together and hanging upside down in a warm, dry location. Keep leaves away from direct light to avoid fading. Seeds can be harvested by placing seed heads in a paper bag and hanging upside down. Shake the seeds out when they have dried and store in a sealed container.
Fun Fact: Many cultures have used fennel seeds as an appetite suppressant. They were utilized in Medieval England by church-goers as a way to deal with hunger pangs on days of fasting.
Preserve: Seeds and leaves may be dried by keeping in a dry, dark place. Aside from hanging upside down to dry, leaves may also be placed in the oven on the lowest temperature setting until completely dry.
Prepare: Frequently eaten raw in the US, many Mediterranean recipes also add fennel seeds, leaves or bulbs to coals when grilling meats or fish to add a distinctive licorice-type flavor. Fennel can also be sautéed, added to stir fries, or used to infuse broths. The leaves may also be used dried in teas.
Nutritional: High in dietary fiber, vitamin C and potassium. The seeds in particular are high in manganese, iron, calcium, and magnesium.
Medicinal: Traditional medicine has used fennel for various ailments, but fennel is most commonly cited as being used in ancient cultures for improving eye sight. Today, there is strong evidence to suggest that fennel is effective in calming the stomach and reducing symptoms of indigestion. Some evidence also exists that supports the claim that fennel can assist in alleviating menstrual cramps and regulating women’s periods.
Warnings: Evidence for the benefits of using fennel vary greatly, particularly for pregnant women. While some sources cite fennel as being effective at treating colic and improving breast-milk production, other sources simultaneously note that it may be toxic to very young children. Consult your physician prior to consuming fennel or feeding fennel to children.
Although basil is commonly associated with pesto, really any green can be turned into a tasty pesto dish, and that includes fennel! Combine your fennel with some pine nuts (walnuts also work great if you’re on a budget) and garlic in a blender and puree. Once smooth, add in some olive oil to break up the consistency. Add salt and pepper to taste.