Ferula spp.

giant fennel

Apiaceae

Mediterranean Basin, North Africa, Middle East, and central Asia

Attracts Pollinators Deer Resistant Drought Tolerant Fragrant (moderate)

SunFull Sun

WaterLow · drought-tolerant

HardinessZones 5–9

Overview

Ferula spp. is a genus of about 170 species of large herbaceous perennials in the carrot family (Apiaceae), distributed from the Mediterranean Basin eastward across North Africa, the Middle East, and central Asia into western China. Plants develop a thick, fleshy taproot and a basal rosette of finely divided, feathery leaves that can reach 12-24 inches (30-60 cm) long, with segments cut into narrow thread-like divisions. Most species are monocarpic: they grow vegetatively for several years, then send up a single stout flowering stem and die after setting seed. Flowering stems range from 3 to 10 feet (0.9-3 m) tall, hollow, and topped with broad compound umbels of small yellow flowers in domed clusters 4-8 inches (10-20 cm) across. The seeds are flattened, winged schizocarps that ripen in late summer. The genus includes F. communis, the giant fennel of Mediterranean hillsides, and F. assa-foetida, whose dried root latex is the source of the culinary spice asafoetida. Sap of several species contains furanocoumarins that can cause skin photosensitization on contact in sunlight. The long juvenile period and single flowering event mean a plant may occupy space for years before blooming, then leave a gap when it dies.

Native Range

Ferula spp. ranges from the Mediterranean Basin and North Africa through the Middle East and Caucasus into central Asia and western China, centered on dry, open hillsides and steppe. No species is native to North America.

Suggested Uses

Ferula spp. is grown as an architectural specimen in dry borders, gravel gardens, and Mediterranean-style plantings, where the tall flowering stems rise above lower plantings. The finely cut foliage fills space in spring before the bloom stem appears. F. assa-foetida is cultivated in parts of Iran, Afghanistan, and India for its resin.

How to Identify

Identified by large, finely dissected, fern-like basal leaves with a strong resinous scent when crushed, rising from a stout taproot. Mature plants produce a tall hollow stem bearing domed compound umbels of small yellow flowers. The combination of feathery foliage, yellow umbels, and a thick perennial rootstock separates Ferula spp. from annual fennel (Foeniculum spp.), which has a more slender form and aromatic seeds used as a spice.

Appearance

Size & Dimensions

Height3' - 10'

Width/Spread2' - 4'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~4 weeks

Spring Summer

Flowering occurs in late spring and early summer, typically May to July depending on elevation and latitude. Each plant blooms only once, after several years of leaf growth, then sets seed and dies. The yellow umbels are visited by short-tongued bees, flies, and beetles.

Detailed Descriptions

Foliage Description

green to blue-green

Growing Conditions

Sun Requirements

SunFull Sun

Requires 6-12 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.0 - 8.0(Neutral)

357912

Soil Types

loam sand rocky chalk

Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Time to Maturity

Several years to first flowering (monocarpic)

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Ferula spp. grows in full sun and sharp, free-draining soil, tolerating poor, rocky, and alkaline ground once established. Most species are drought-tolerant and prone to rot in cold, wet winter soils that damage the fleshy taproot. Plants are raised from fresh seed sown in autumn, as the taproot makes transplanting of older specimens difficult. After germination they need several seasons of undisturbed growth before flowering. Watering is reduced to almost nothing during summer dormancy in Mediterranean-climate gardens. Sap contact combined with sunlight can cause skin irritation in some people.

Pruning

Routine pruning is not required. Spent flowering stems are cut to the ground after seed ripens, at which point monocarpic plants have completed their life cycle. Removing seed heads before they shatter limits self-sowing where seedlings are not wanted.