Bull Thistle

Cirsium vulgare

Copyright, Peter Sforza

Bull Thistle is a prickly wildflower which most people consider an annoying weed. Its stems, branches, and leaves are covered with spikes and you should be careful when touching it.

Bull Thistles have pretty purple to pink flowers, one to two inches wide. Leaves are three to six inches long. Bull Thistles can reach six feet tall.

This plant, which is in the Sunflower family, can grow in fields, gardens, and roadsides. Bull Thistle is an introduced plant, but is now common.

Bull Thistle blooms from July to September.

After the flower has finished blooming, the fruits produce "thistledown," small seeds with fluffy stuff on them. This type of seed is called an "achene."

Achenes are transported by wind to new places so new Bull Thistles can grow.

Copyright, Peter Sforza

Robert W. Freckmann, Wisconsin State Herbarium

The Bull Thistle is a biennial plant, which means it lives for two years and then dies. The first year it grows a rosette, a cluster of leaves near the ground. The second year it grows flowers and fruits, spreading seeds before it dies. The pictures to the left show a rosette the first year (top picture), and a dead plant in the winter (bottom picture).

Bull Thistles are a good food source for many animals. Eastern Cottontails and White-tailed Deer eat the leaves and stems. Flower nectar is consumed by hummingbirds, bees, and butterflies. Seeds are popular with many birds, such as American Goldfinches and Juncos, as well as mice and other small mammals.

Hummingbirds and insects help pollinate Bull Thistles by accidentally gathering pollen from one plant, and delivering it to the next one they visit.

Relationships in Nature:

Animals Using as Food Source

Animals Using as Shelter

Associations With Other Plants


Ruby-throated Hummingbird

American Dog Tick

Common Milkweed

Ruby-throated Hummingbird Po

Painted Lady

Chinese Mantid

Smooth Crabgrass

Painted Lady Po

Meadow Vole

Painted Lady


Mourning Cloak Po

Eastern Cottontail

American Goldfinch

Red Clover

Honey Bee Po

White-tailed Deer

Black and Yellow Argiope

Common Dandelion

Golden Northern Bumble Bee Po

American Goldfinch

Carolina Chickadee

Common Reed

Eastern Tiger Swallowtail Po

Dark-eyed Junco

Green Lacewing

Spotted Joe-pye Weed

Clouded Sulphur Po

Black Carpenter Ant

Six-spotted Tiger Beetle

Lamb's Quarters

Hummingbird Moth Po

Mourning Cloak

Common Ragweed

Green Lacewing FP

Honey Bee

Bushy Aster

Pipevine Swallowtail Po

Golden Northern Bumble Bee

Kentucky Bluegrass

Organ-pipe Mud Dauber Po

Eastern Tiger Swallowtail

Common Mullein

Cicada Killer

Eastern Yellow Jacket

Clouded Sulphur

Hummingbird Moth

Green Lacewing

Pipevine Swallowtail

Organ-pipe Mud Dauber

Relationship to Humans:

Bull Thistles are helpful to people who want to attract wildlife, especially birds and butterflies. Therefore many people plant them in their gardens. To others it is a weed, and an obnoxious one. If you are going to try to pull one up, wear gloves. The spikes are sharp and the roots are strong.


Cirsium vulgare


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