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Fennel

Foeniculum vulgare

Vegetables

Florence fennel produces a crisp, anise-flavored bulb. Keep well watered to prevent bolting and plant away from most other vegetables.

Overview

SunFull Sun
WaterMediumCalculate watering amount
Height40–60 cm
Spread25 cm
Spacing30 cm
Row Spacing40 cm
Germination7–14 days
To Harvest65–90 days

Companion Planting

Good Companions

None

Toxicity

SeverityNon-toxic

Non-toxic to humans, dogs, and cats (ASPCA-listed safe plant). Large quantities may cause mild gastrointestinal upset; concentrated fennel essential oil should be avoided.

Planting Tips

LocationFull sun in a warm, sheltered spot; avoid planting near dill or coriander to prevent cross-pollination and inhibited growth.
SoilWell-drained, loamy, humus-rich soil with a pH of 6.5–8.0.
Sowing Depth1 cm
Planting Depth3 cm
WateringKeep soil consistently moist but never waterlogged; water when the top 5 cm dries out, as drought stress causes premature bolting.

1 cm of water per m² equals 10 liters. Use the Watering Calculator for exact amounts.

FertilizingApply moderate compost or a balanced 10-10-10 fertilizer at planting and once mid-season; avoid excess nitrogen to prevent nitrate buildup.

Care Tip: Thin seedlings to 30–45 cm apart for good air circulation; hill soil around bulb fennel bases to blanch and sweeten the bulbs.

Common Pests

Aphids

Symptoms: Clusters of small soft-bodied insects on stems and leaf undersides causing curled, yellowed, or stunted foliage and sticky honeydew residue.

Treatment: Blast off with a strong water spray or apply insecticidal soap; for heavy infestations use neem oil.

Prevention: Encourage natural predators like ladybugs and lacewings; avoid excessive nitrogen fertilization that promotes tender growth.

Slugs and Snails

Symptoms: Irregular holes in leaves and slime trails on and around the plant, especially on young seedlings.

Treatment: Hand-pick at dusk or use iron-phosphate-based slug pellets around plants.

Prevention: Remove debris and hiding spots near plants; use copper tape barriers or coarse mulch around the base.

Parsleyworm (Black Swallowtail Caterpillar)

Symptoms: Large, striped green-black-yellow caterpillars visibly feeding on foliage, causing significant defoliation.

Treatment: Hand-pick caterpillars and relocate them; use Bacillus thuringiensis (Bt) spray for severe infestations.

Prevention: Inspect plants regularly; plant extra fennel to share with beneficial swallowtail butterflies, or use row covers on young plants.

Common Diseases

Cercospora Leaf Blight

Symptoms: Small, dark brown to gray spots with yellow halos on leaves that expand and merge, leading to leaf dieback.

Treatment: Remove and destroy affected foliage; apply a copper-based fungicide if infection is severe.

Prevention: Ensure adequate plant spacing for air circulation; practice crop rotation and avoid overhead watering.

Powdery Mildew

Symptoms: White, powdery fungal coating on leaves and stems, causing yellowing, distortion, and reduced vigor.

Treatment: Spray with a sulfur- or potassium-bicarbonate-based fungicide; remove heavily infected plant parts.

Prevention: Provide good air circulation by proper spacing; avoid excessive nitrogen and water at the base rather than from above.

Root and Crown Rot

Symptoms: Wilting despite moist soil, yellowing lower leaves, soft or darkened stem bases, and a foul smell from decaying roots.

Treatment: Remove and dispose of affected plants; improve drainage and avoid replanting in the same spot for at least two years.

Prevention: Plant in well-drained soil, avoid overwatering and waterlogged conditions, and rotate crops annually.