Boundary Invasive Species Society
A tall biennial growing to 3 m (6 ft) tall with a stout taproot. Flowering stalks have stout branches. Originally from Europe and North Africa.
• Pale purple flowers borne in dense heads forming a cone.
• Long bracts surround the flower head.
• Leaves have obvious veins with stiff prickles.
• Leaves in opposite arrangement on flower stem.
Prefers moist sites and is of high concern in riparian areas, along irrigation ditches and canals. Cones dried for flower arrangements.
Hand pulling or digging is effective if entire root is removed. Best done when soil is moist. Wear gloves, avoid skin contact. If any portion of flower is beginning to emerge, or if seed heads are formed, pick, bag, and remove. Selective herbicides are effective.
Reproduction and Dispersal:
Reproduces only be seed. Seeds can be moved by water, soil, mowers and animals to new locations.
Thrives in open, sunny habitats with moist soils but can tolerate wet and dry conditions. It can create large dense stands in pastures and fields.
Cone like flower heads can be up to 10 cm
tall. The cone is a cluster of small pale purple
flowers. The cone like flowers occur singly on
tops of stems. The flowers are surrounded by
long bracts that form a cage around the cone.
Leaves and Stems:
Leaves arranged opposite on the flower stem.
The stem is stiate-angled with several rows
of downward pointed prickles. Leaves with
obvious white veins and stiff prickles on the
lower mid rib of the leaf. Basal leaves typically
die early in the second season as the flower
Small seeds develop inside the flower
cone and are released when the cone is
disturbed. Most seeds fall close to the parent
plant. Can produce up to 34,000 seeds per
Large woody taproot up to 0.6 m long
and 3 cm across at the root crown.