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Fennel (Foeniculum vulgare)

Foeniculum vulgare is an upright, aromatic, branching herbaceous plant. Sources differ in describing its life cycle: it ranges from biennial to perennial and is also commonly grown as an annual for food cultivation.

LightFoeniculum vulgare prefers full sun.
WaterIt prefers moist but well-drained soil and, once established, can tolerate drought and alternating dry and wet conditions.
TemperatureIt is frost hardy. It is generally reported to have an RHS H5 hardiness rating.
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Fennel illustration

Overview

Foeniculum vulgare is an upright, aromatic, branching herbaceous plant. Sources differ in describing its life cycle: it ranges from biennial to perennial and is also commonly grown as an annual for food cultivation.

Origin and habitat

Sources differ on the native range: its core native area includes the Mediterranean region, while broader accounts extend through southern Europe, North Africa, and western Asia to Pakistan. It is commonly found in dry soils near coasts and along riverbanks and can also grow in dry, rocky, calcareous soils. It is adapted to Mediterranean-type to warm-temperate climates, is cold tolerant, and has become naturalized in many temperate or Mediterranean-type climate regions worldwide.

Characteristics

Sources differ on mature height, placing it at about 100–250 cm, while mature spread is 10–50 cm. The finely divided, feathery leaves have threadlike or needlelike terminal segments and sheathing leaf-stalk bases. Small yellow flowers form terminal compound umbels, with many small flowers in each inflorescence; sources differ on flowering season, describing it mainly as summer flowering but sometimes extending into early autumn depending on region or cultivation conditions. The dry, splitting fruit separates into segments when mature, has conspicuous longitudinal ribs or grooves, and commonly changes from green through yellowish brown and brown to darker colors.

Light

Foeniculum vulgare prefers full sun.

Watering

It prefers moist but well-drained soil and, once established, can tolerate drought and alternating dry and wet conditions.

Temperature and dormancy

It is frost hardy. It is generally reported to have an RHS H5 hardiness rating.

Growing medium and mounting

It is suited to well-drained clay, loam, sand, and chalky soils, with sources supporting acidic, neutral, or alkaline conditions.

Propagation

It is propagated by seed; sources differ in recommending direct sowing in spring or, in Taiwan cultivation guidance, sowing fresh seed after cooler autumn conditions begin.

Common problems

Wild plants can develop galls caused by gall midges; seeds can also be affected by gall midges, some orthopteran insects can lay eggs in stems, and butterfly larvae including swallowtails can feed on the leaves. Sources differ on its status, but it can readily self-seed, escape cultivation, and naturalize, becoming an invasive weed that forms dense stands in some regions. It tolerates cold and has some drought tolerance once established, but has difficulty surviving summer under Taiwan's humid and hot conditions.

Identification

Foeniculum vulgare is generally reported to have upright, hollow stems and an aromatic habit, with extremely fine, threadlike, feathery leaves and yellow compound umbels; it resembles dill in appearance but is usually taller.

Photos

Foeniculum vulgare
📷 Ryan Hodnett · CC BY-SA 4.0 · source
Foeniculum vulgare
📷 Elekes Andor · CC BY 4.0 · source

Sources