How to Grow Fennel Herb from Seed
- Scientific Name: Foeniculum vulgare
- Hardiness Zone: Annual, Perennial to Zones 4-9
- Days to Harvest: 60-90 days
- Days to Maturity: 90 days
- Days to Germination: 8-12 days
- Seeding Depth: ¼”
- Plant Width: 18-36"
- Plant Height: 48-72"
- Growth Habit: Tall bushy upright with bulbous root base
- Soil Preference: Organic, medium moist, well-drained
- Temp Preference: Warmer, 60-85°F
- Light Preference: Full sun
- Pests/Diseases: Susceptible to rot and mold in overly saturated soils, watch for leaf-eating insects like slugs and caterpillars
- Availability: See All Fennel Varieties
Fennel, native to southern Europe, is a short-lived perennial that may be considered an annual in zones that have heavy winters with temperatures that regularly fall below 15°F. It may also be chosen to be grown as an annual by gardeners in warmer zones, as well, but is a perennial by definition. It grows best in its second year and while it self-seeds and is an aggressive grower, is not considered invasive. Fennel can grow up to 6 feet tall and has an extensive history of being used medicinally by ancient civilizations. Throughout the Middle Ages, it was believed to be capable of curing ailments ranging from inflammation to pulmonary issues. It was also believed to ward off evil spirits.
How to Grow Fennel from Seed
- Wait until the last spring frost date to sow seeds
- Germination should occur in 8-12 days
- Extremely hardy and tenacious once established
To grow fennel from seed, wait until the last spring frost date to sow seeds. Seeds can also be sown indoors, under a grow light, around 4 weeks before the last frost date and then transferred to a garden. Sow seeds about ¼” deep in soil, planting them 6-12" apart. Germination should occur in 8-12 days. Fennel prefers a soil that is rich and well drained, with a pH of 5.5 to 6.8. It does well in soil that has compost or organic matter sifted in, as this gives it more nutrients to grow and thrive. Fennel prefers full sun, with a minimum of six hours a day. It also requires to be watered regularly and consistently, but not enough to oversaturate its roots as this can lead to root rot.
Fennel prefers soil that is rich and well drained. It prefers moist that is fertile and acidic with a pH of 5.5 to 6.8. Fennel grows best in soil that has been mixed with organic matter and is lightly fertilized every so often. To ensure that the soil is moist, water it regularly and check it for dryness as needed. Fennel prefers soil that is moist yet not too damp, as this can rot its roots. It needs just enough water to reach its roots.
- Requires frequent watering
- Prefers consistently moist, well-drained soil
- Susceptible to mold and rot in overly saturated soils
Fennel needs watered regularly, requiring at least 1" of water a week, but more in hotter weather conditions. However, during rainy weather, it may require less. To check if its soil needs watered, stick fingertips in it to check moisture levels. If the top inch of soil feels dry, it is time to water it. Fennel prefers moderate climates with cooler weather but will tolerate some heat and cold. It may differ among variations of fennel, but fennel typically does not tolerate dry conditions as it thrives in moist soil.
Is Fennel A Perennial?
Fennel is a short-lived perennial, meaning that its lifespan will reach around 3-5 years before it needs restarted from another seed and germinated again. While fennel is considered a perennial, it may be considered and grown as an annual in zones that have heavy winters with temperatures that regularly fall below 15°F. It may be grown as an annual in warmer climates as well from the choice of the gardener but is still considered to be a perennial plant as it readily reseeds itself.
Fennel in Winter
- Is considered a hardy perennial
- Established plants can go dormant in winter
- May be brought indoors to overwinter
Fennel is considered to be a hardy perennial and can withstand colder temperatures up to light frosting but is not fond of the cold. If exposed to too much cold it will die back to ground level but can tolerate temperatures to 0 degrees F. Fennel is not a cold season crop and because of this, is not tolerant of anything but mild winter conditions. In such conditions, it is best suited to be potted and placed indoors, as this will provide more adequate conditions for its growth.
Growing Fennel in Pots
Fennel grows well in pots, as long as the pot is big enough. Since fennel produces a long taproot, it needs a great deal of depth in terms of height and width both. You may gradually move up to larger pot, but since fennel can grow up to 6 feet in height, it’s important to be prepared to invest in a large pot to hold its roots. When potting fennel, use a soil that is well-draining and loamy. Since pots are known to dry soil out quickly, by having a soil that is loamy it will more easily retain moisture. Make sure that the pot has an adequate number of draining holes at the bottom to ensure that the soil stays well-drained, and water doesn't sit at the bottom of the pot. If this were to happen, the plant would be at risk for root rot which happens when roots are over saturated with water when it is not needed. Water fennel regularly.
How to Care for Fennel Plants in Pots
- Make sure it receives water regularly
- It needs full sun, up to 6 hours a day
- Careful not to overwater and saturate
When growing fennel in a pot, make sure to water fennel regularly and ensure that it receives at least 6 hours of sunlight a day. Fennel, once established, does not need much maintenance or upkeep. Be careful to not overwater it, as this can cause root rot. This can be avoided by making sure the drain holes in pots are properly draining and that the soil is moist but not too damp to the touch.
Growing Fennel Indoors
Fennel is not commonly grown indoors compared to how much more often its' grown outside. This may partly be due to fennel being able to reach heights of 6 feet tall. Since it grows so tall and quickly, within around 90 days, it can be difficult to place in one's living space while attempting to regularly receive enough sunlight. Since pots are normally placed in areas such as windowsills, kitchen tables, and other areas to receive sunlight through windows or transparent surfaces it may be helpful to add a growing light once fennel has reached optimal heights since it will likely not sit on a windowsill or a table comfortably at that point.
Fennel Companion Planting
Fennel does not make a good companion plant for most plants, as it secretes a substance from its roots that inhibits the growth of the plants around it. Fennel is particularly effective in inhibiting the growth of beans and tomatoes if planted near them. However, fennel does attract bees with its flowerheads that are rich in nectar and pollen. Fennel may be helpful to plant by itself in a flowering garden as it attracts pollinators, as long as it is far away from other plants to ensure that its roots are not near other plants to cause them harm.
Fennel sprouts bright, yellow flowers with feathery leaves that are wispy in texture and appearance. Its flowers have a yellow center and leaves, with the scent commonly described as that of anise or licorice. These flowers are highly attractive to bees and other pollinators due to their high content of nectar and pollen.
Fennel is best harvested with scissors or shears to ensure a clean cut. It is best harvested after about 90 days of growth, but its leaves may be harvested as soon as the plant becomes established. Be sure to not take more than a handful of leaves at a time, up to 1/3rd of the plants overall mass at the most because if more is taken, this will inhibit its future growth. It is harvested simply by cutting away the feathery foliage.
When to Harvest Fennel
- When its flowers have fully bloomed
- After about 90 days from seeding
- When plant is mature enough to safely harvest a third of its overall mass
How to Harvest Fennel
Fennel is harvested by cutting the stems of the flower, obtaining its leaves and flowers. While many herbs are recommended to not let their flowers bloom fully before harvesting, this issue does not carry over to fennel. Fennel's flowers are commonly used in harvesting as they are known to have a pleasant smell and taste. When harvesting fennel, simply cut it with scissors or shears.
Fennel may be dried using multiple methods, whether it be hung and dried, dried on a screen, oven dried, or dried in a food dehydrator. If hang drying it, tie the fennel together and hang it upside down in a dry, dark room for a week or two. After this time is up, its leaves, seeds, and flowers will be easily harvested from the dried plant. To oven dry fennel, you may place it in an oven heated up to 200°F for up to 3 hours. Once it is finished drying in the oven, allow it to cool off completely. If drying in a food dehydrator, place the fennel or its desired part whether it be its leaves or flowers on a drying rack while the food dehydrator preheated to its lowest temperature, around 95-115°F and slowly dehydrate it. This may take multiple hours but since fennel carries a lot of moisture within it, this process helps prevent moldy and maintain its overall essence.
How to Dry Fennel
Hang Dry: If hang drying it, tie the fennel together and hang it upside down in a dry, dark room for a week or two. After this time is up, its leaves, seeds, and flowers will be easily harvested from the dried plant.
Oven Dry: To oven dry fennel, you may place it in an oven heated up to 200°F for up to 3 hours. Once it is finished drying in the oven, allow it to cool off completely.
Food Dehydrator: If drying in a food dehydrator, place the fennel or its desired part whether it be its leaves or flowers on a drying rack while the food dehydrator preheated to its lowest temperature, around 95-115°F and slowly dehydrate it. This may take multiple hours but since fennel carries a lot of moisture within it, this process helps prevent moldy and maintain its overall essence.
Types of Fennel
There are around 7 different varieties of fennel, grouped within two major types. The two major types of fennels are herb fennel and vegetable fennel (Florence fennel). Herb fennel is known for three common varieties: sweet fennel, rubrum, dulce, and purpureum. Sweet fennel is true to its name and has a sweet taste, making it popular to be taken in teas and tinctures. Rubrum has bronze leaves, which is distinctive to it. Its flowers are golden in color and rubrum is used frequently in culinary practices and dishes. Dulce is a green colored fennel, and purpureum is characterized by its purple leaves and is largely ornamental as an herb. For vegetable fennel, there are four common varietes: rhondo, cantino, victoria, and mantavo. Rhondo is characterized by its uniformly round bulbs that are spherical in nature, cantino is known for its slow growth, victoria has a stronger resistance than the other varieties to bolting and is an aggressive grower, while mantavo is known for yielding prosperously and is a slow bolting variety of fennel.
Benefits of Fennel
Fennel is highly regarded as a medicinal and culinary herb, as it can relieve the body from common ailments that plague it. Among these ailments, fennel is known to relieve gas, act as a diuretic, boost metabolism, treat hypertension, and can benefit heart health. Fennel is also very nutritious, as it contains significant levels of vitamin c, calcium, iron, magnesium, potassium, and manganese. It is also very low in calories, clocking in at about 27 calories for one cup of raw fennel bulb and 20 calories for one cub of dried fennel seeds. It may act as a diet suppressant when consumed and since it has such a low-calorie content, may be ideal for people who are looking for a highly nutritious addition to their diet that will support a low-calorie diet easily.
Additional Information on Fennel
- Fennel Wikipedia Page
- Read the Best Practices for Planning Your Herb Garden!
- Learn About Hardiness Zones
Explore these Fennel Herb Seed Varieties: