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Carduus pycnocephalus

Italian thistle

Asteraceae Mediterranean and western Asia

Attracts Pollinators Attracts Butterflies Deer Resistant Drought Tolerant

Overview

Carduus pycnocephalus is a spiny annual or winter-annual thistle, sometimes biennial, growing 8-80 in (20-200 cm) tall, with erect, branched stems edged by spiny, leaf-like wings. The deeply lobed leaves are 2-8 in (5-20 cm) long, green with a thin cobwebby coating beneath, and tipped with sharp yellow spines along the margins. From spring into summer the plant carries small, narrow flowerheads 0.5-0.8 in (12-20 mm) long, usually grouped two to five together at the branch tips, each holding tubular pink to purple florets above a spiny, cobwebby base. Each head produces many small seeds tipped with slender white bristles that disperse on the wind. The plant forms a basal rosette in autumn or winter, bolts and flowers in spring, then dies after setting seed. It establishes quickly on disturbed, overgrazed, and roadside ground, forming dense, spiny stands that crowd out other vegetation, and is listed as a noxious or invasive weed in California, Australia, and elsewhere. It grows from a stout taproot and relies on prolific seeding rather than perennial regrowth.

Native Range

Native to the Mediterranean region and western Asia, from southern Europe and North Africa east to the Middle East. It has naturalised as a weed in North and South America, southern Africa, and Australia.

Suggested Uses

This species is not cultivated and is treated as an agricultural and environmental weed. It has no recognised ornamental or horticultural use.

How to Identify

Recognised by spiny-winged stems and deeply lobed, spine-tipped leaves with a thin cobwebby coating beneath. The narrow flowerheads are small, 12-20 mm long, and clustered two to five together at the stem tips, with pink to purple florets. The slender, cobwebby flowerheads separate it from the broader, solitary heads of Carduus nutans.

Appearance

Size & Dimensions

Height8" - 6'8"

Width/Spread1' - 2'

Colors

Flower Colors

pink

purple

Foliage Colors

green

Bloom Information

Bloom Period

~10 weeks

Spring Summer

Flowering runs from mid spring into summer, broadly April to July depending on climate. The small clustered heads open over several weeks as the stems branch and extend. Seed ripens quickly after flowering and sheds through summer.

Detailed Descriptions

Foliage Description

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 Range5.5 - 8.0(Neutral)

357912

Soil Types

loam clay sand rocky

Drainagewell drained

Water & Climate

Water Needs

Low

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Carduus pycnocephalus grows in full sun on a wide range of soils, including poor, dry, compacted, and disturbed ground. It germinates after autumn rain, overwinters as a rosette, and grows rapidly in spring. The plant tolerates drought and grazing pressure, which gives it an advantage on overgrazed pasture. It needs no cultivation and is managed as a weed rather than grown. Removing rosettes before stems bolt and flower limits the heavy seed production that drives its spread.

Pruning

No pruning is required for this weed. Plants are cut, mown, or pulled at the rosette or early flowering stage to prevent seed set. Cutting after seed has formed spreads the bristly seed rather than controlling it.