Fennel

Sun

Full sun; stems become weaker and flowering decreases in shade.

Water

Water regularly while establishing, then during prolonged dry spells. Established plants tolerate some drought; avoid waterlogged soil.

Soil

Well-drained soil, preferably moderately fertile; tolerates sandy, stony and chalky ground.

Height

4-6 ft (1.2-1.8 m)

Spread

1.5-3 ft (0.45-0.9 m)

Flowers

Summer into early autumn; small yellow flowers in broad, flat-topped clusters.

Foliage

Finely divided, threadlike green leaves with an anise scent; bronze-leaved forms are also grown. Usually dies back in cold winters but may retain foliage in mild climates.

Growth

Fast

Care needed

Medium

• Pollinators
• Drought tolerant
• Cold hardy
• Heat tolerant
• Wildlife
• Low allergen
• Fragrant
• Edible

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   3 ft (0.92 m)

3. After 2 years

   5 ft (1.5 m)

   full size

About 2 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Invasive in

the US and Australia

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Fast

• Sow directly or plant young seedlings; the deep taproot makes established plants difficult to move.
• Water young plants deeply when the soil begins to dry, and established plants during extended drought.
• Avoid heavy feeding, which encourages soft, floppy growth; a light spring dressing of compost is usually enough.
• Stake tall plants early in exposed gardens, or support them among sturdy border plants.
• Remove unwanted seedlings promptly and cut off seed heads before they ripen where spreading is a concern.

Pruning. Cut spent flower heads off before the seeds mature unless you want to harvest seed or allow self-sowing. Cut dead stems to ground level in late winter or early spring before new shoots lengthen.

Snip fennel fronds as needed once plants are established and about 6–8 inches (15–20 cm) tall, taking only a few stems at a time. For Florence (bulb) fennel, cut the swollen base at soil level when it is firm and about 3–4 inches (8–10 cm) across, usually 3–4 months after sowing, before a flower stalk develops. Harvest seeds in late summer or autumn when the seed heads turn brown but before seeds fall;

Late winter

Cut down dead stems and check that the crown is not sitting in wet soil.

Spring

Direct-sow once the soil is workable and warming; thin seedlings to 1.5-2 ft (0.45-0.6 m) apart.

Late spring

Install supports in windy sites and remove unwanted volunteer seedlings.

Summer

Harvest small quantities of leaves and water during prolonged dry weather.

Late summer

Remove fading flower heads to prevent seeding, or collect seed heads as the seeds turn brown.

Autumn

Leave sound, seed-free stems for structure and insects, or remove broken stems.

• Place near the back of a sunny border, where the fine foliage softens larger leaves without creating a solid visual barrier.
• Combine with coneflowers, yarrow and upright salvias for contrasting flower shapes and a long season of insect activity.
• Use in a herb garden or potager for accessible leaf and seed harvesting.
• Plant among drought-tolerant perennials in a gravel garden, allowing room for its mature height and spread.

Garden styles it suits: Cottage garden, Potager (kitchen garden), Mediterranean, Dry gravel garden, Pollinator garden and Edible landscape.

Plant it with: Yarrow, Purple coneflower, Meadow sage, Tall verbena, Lavender and Feather reed grass.

Wildlife: Flowers feed hoverflies, small parasitic wasps, bees and other insects. In North America, the foliage is a host plant for black swallowtail and anise swallowtail caterpillars; tolerate some leaf loss rather than spraying them.

• Excessive self-seeding: remove flower heads before seeds ripen and pull seedlings while their roots are small.
• Aphids on tender shoots: rinse off heavy colonies with water and preserve ladybirds, lacewings and other predators.
• Crown or root rot in wet soil: improve drainage or replant in a raised position; avoid frequent watering of established plants.
• Flopping stems: provide full sun, avoid rich feeding and stake early in exposed positions.

Fennel is not known to be toxic to cats, dogs or horses. Its leaves, seeds and Florence fennel leaf bases are edible to people in normal food quantities. Concentrated essential oil is not equivalent to the edible plant and should not be given to pets or taken internally without qualified advice.

Where it spreads. Spreads readily by seed. It is invasive in California and is also a weed concern in parts of Oregon and Washington. In Australia it is an environmental weed in parts of New South Wales, Victoria, South Australia, Western Australia and Tasmania. Check local restrictions before planting, especially near roadsides, grassland or coastal habitat.

• Dill (Anethum graveolens)

  Also has fine foliage and yellow flower clusters, but is an annual, usually smaller, with a dill rather than anise scent. Its ripe seeds are broad and flattened; fennel seeds are longer and prominently ribbed.

• Poison hemlock (Conium maculatum)

  Highly poisonous. It has white rather than yellow flowers, broader fernlike leaf segments and usually purple-blotched stems. Never taste an unidentified plant or rely on smell alone to identify edible fennel.

• Dogfennel (Eupatorium capillifolium)

  Has similarly fine foliage but produces numerous small whitish flower heads rather than broad yellow umbels. It is not edible fennel and should not be used as a substitute.

Foeniculum comes from the Latin for 'little hay', referring to the fine foliage or its scent, while vulgare means common.

Propagation. Direct-sow seed in spring, or in autumn where winters are mild. Transplant only small seedlings with minimal root disturbance; division is generally unsuccessful because of the taproot.

Accepted botanical name

Foeniculum vulgare

In the US and Canada

Introduced in Canada, Hawaii, the lower 48 states, Puerto Rico and US Virgin Islands.

Native range

Afghanistan, Albania, Algeria, Baleares, Bulgaria, Corse, Cyprus, East Aegean Is., Egypt, Eritrea, Ethiopia and France.

Measured

Soil pH 7.5 to 8. Average height 89 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.