Common cocklebur

Xanthium strumarium

At a glance
Type	Broadleaf
Life cycle	Summer annual
Family	Aster family (Asteraceae)
Origin	Native to the US
Most common in	Southeast, South Central, Midwest, Great Plains

About

A coarse, bushy native summer annual best known for its hooked burs that cling to fur, wool and clothing. Its seedlings and seeds are poisonous to livestock.

Also called cocklebur, rough cocklebur, clotbur

How to identify it

Look for

Seedlings have long, narrow, shiny seed leaves and a purple stem base. Grown plants reach 1-4 feet with thick stems spotted purple or black, and rough, sandpapery, triangular to heart-shaped leaves with toothed edges on long stalks. Egg-shaped woody burs about 1 inch long are covered in hooked prickles, end in two beaks, and hold two seeds.

Where it grows

Moist, disturbed ground such as ditches, river bottoms, pastures, crop fields, gardens and roadsides; it handles both flooded and dry soil.

When

Sprouts mid-spring to early summer once the soil is warm (about 63°F), starts flowering as days shorten (usually from August), and ripens burs into fall.

How it spreads

By seed in burs that hitch rides on animals and clothing; each bur's two seeds sprout in different years, and a vigorous plant can make 500-5,400 burs.

Most common in

Northeast	Common here
Southeast	Very common here
South Central	Very common here
Midwest	Very common here
Great Plains	Very common here
Mountain West	Common here
Southwest	Common here
Pacific Northwest	Common here
California	Common here
Alaska	Not found here
Hawaii	Occasional here

Where it is regulated

Cocklebur seeds (Xanthium species) are noxious weed seeds under state seed laws in states including Alabama, Arkansas and Georgia (prohibited) and Arizona, Delaware, Florida, Hawaii and Kansas (restricted).

What to do, gentlest first

Protect yourself first. Weed killers are a last step; always read and follow the label.

Wipe out edge patches early Prevent
Cocklebur often gets started in unmanaged corners first, so remove it there before it can seed into your beds.
Hoe early, pull before burs form By hand
Hoe or pull seedlings early and repeat as new flushes come up. Pull any larger plants before burs ripen.
Wear gloves; bag burs instead of composting them.
Solarize bare beds Barrier
Solarizing moist soil under clear plastic so midday soil temperatures reach about 149-156°F kills a high share of cocklebur seeds.

Uses, wildlife and pets

For wildlife

Not a significant food source for pollinators or wildlife, though many insects use it.

Pets

Not listed by the ASPCA. Seedlings and seeds poison cattle, pigs, sheep and poultry, and the burs tangle in pet fur.

Sources

Photo: Photo: George Chernilevsky / Wikimedia Commons, CC BY 4.0 (CC BY 4.0). Photo resized for the web.

Planting dates and advice are general guidance; check with your local Cooperative Extension office for your area.