Growing Guide
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Herbaceous Perennial Flower, Herb

Also known as Sweet fennel, Wild fennel, Copper fennel, Bronze fennel
Foeniculum vulgare
Apiaceae Family
Synonym: Foeniculum officinale, Foeniculum capillaceum, Foeniculum foeniculim, Foeniculum vulgaris

The dark, fine-textured foliage of this short-lived perennial herb combined with its height (up to 6 feet tall) make it a great background for borders or herb gardens. It attracts beneficial insects and feeds the catepillars that morph into swallowtail butterflies.

Site Characteristics
  • full sun

Soil conditions:

  • tolerates acid soil
  • tolerates droughty soil
  • requires well-drained soil
Prefers rich, moist but well-drained soil, but will tolerate drought. Tolerates wide range of pH 4.8 to 8.2.

Hardiness zones:

  • 4 to 9
Plant Traits

Lifecycle: perennial

Short-lived perennial, but reseeds easily.

Ease-of-care: easy

Height: 3 to 6 feet

Spread: 1 to 2 feet

Larger, solitary plants may spread up to 3 feet.

Bloom time:

  • mid-summer
  • late summer

Flowering starts about 90 days from spring seeding.

Flower color: yellow

Foliage color: dark green

Foliage texture: fine

Foliage is feathery and thin, but dense enough that massed plants form solid dark background.

Shape: upright

Shape in flower: same as above

Special Considerations
  • wind - But not salty winds off the ocean.
Special characteristics:
  • aggressive - Self-sows and can become a weed problem if not deadheaded. Some seeding is helpful to replace older plants.
  • non-invasive
  • not native to North America - Native to southern Europe.
  • fragrant - The whole plant is anise-scented, the young foliage having a specially pungent anise-like flavor and fragrance. Dried seed is sweetly fragrant, although fresh seed has a slightly unpleasant smell.
  • beneficial insects - Flowering plants attract bees, parastic wasps and hoverflies.
Special uses:
  • edible landscaping
Growing Information
How to plant:

Propagate by seed, division or separation - Propagation by seed is easy. Plants self-sow readily. Sow seeds where you want them in the garden in spring or fall.    You can also start seed inside. Soak seed for 4 to 5 days to increase germination.

Division is difficult because of long tap root. Fall division is best.

Maintenance and care:
Cut back plants to force them to become bushier. If they get too leggy stake them.

Deadhead to prevent aggressive reseeding. Some seeding is desirable to replace plants that die. (Fennel is a short-lived perennial.)

Flowers attract beneficial insects, so don't cut them before they start to fade. Foliage is also a favorite food of the catepillars of swallowtail butterflies.

Cut plants back to the ground after hard freeze.

Caution: Contact with plant juices and exposure to sun can cause skin irritation.

More growing information: How to Grow Perennials

Larvae of swallowtail butterflies
Slugs and snails
Disease is rarely a problem. Some potential problems include:

Cercospora leaf spot
Powdery mildew

'Purpureum' ('Bronze') has purplish-bronze foliage when young, becoming waxy as it matures.

Florence fennel (F. vulgare var. azoricum) is a tender biennial usually grown as an annual for its swollen, bulb-like stem bases that are eaten as a vegetable. Often called finnochio in Italy, it needs a long, cool season to grow and is usually much shorter than fennel.