Bull Thistle

Due to its size, spines and rapid spread, bull thistle (Cirsium vulgare) is considered an aggressive weed or noxious plant. Its seeds are wind dispersed, are viable for over ten years and each plant can produce over 10,000 seeds with a germination rate of 95% resulting in dense patches that resist eradication.

Native to Eurasia, this member of the Sunflower Family (Asteraceae) can now be found throughout most of North America, including Alaska. Its habitat includes pastures, dry meadows, roadsides and disturbed, overgrazed and logged areas.

A biennial, bull thistle arises from a short, fleshy taproot. The one to six foot stem is branched, widely spreading and spiny winged. The leaves are strongly lobed with spines on the margins. The upper side is sparsely prickly above and cottony below. The lower leaves can be as much as sixteen inches long.

Bull thistle flowers are more or less clustered at the terminal ends of the stem branches. Each flower head consists solely of reddish-purple disk flowers surrounded by narrow, spine-tipped phyllaries. The straw colored bull thistle seeds have brown or black lengthwise stripes, a protrusion at one end and are tipped with plume-like hairs.

Because of its spiny nature, bull thistle is considered unpalatable to livestock and wildlife. However a few references (ex: Charles Johnson in a 1993 Forest Service Publication) state that despite the spines the flower heads can be and are eaten by cattle, elk and horses.

The thicker stems of bull thistle are edible when peeled, although peeling the stems is a challenge because of the spines. As a child I would often peel bull thistle stems and eat them. The peeled stems taste like celery and have the crisp texture of jicama. Once you get past the spines, bull thistle is a good trail snack.

This bull thistle plant was photographed in July near the Tule River boat launch (Shasta County CA).

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5 Responses to Bull Thistle

  1. tonytomeo says:

    I believe that the foliage is edible also, like that of the milk thistle. I just have not bothered to try it because it would be so much work to remove all the thorns. There are better and easier greens to eat. I would need to be very hungry to bother with this.

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    • Jim Gordon says:

      I was going to add to your vast fund of knowledge by my observation of Horses loving the flower heads. They roll their lips back and carefully pluck the head from the stem. I would remind the that I was the pilot and used a light tap of my reins. Total failure, while they never attempted steal a flower again they would jump past the plant to avoid my correction.

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      • tonytomeo says:

        Well, at least some do not go to waste.
        When such thistles appear here, we dig them immediately, or at least cut them down before they disperse seed. It seems like such a waste to just leave them where they fall.

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      • gingkochris says:

        Digging is definitely preferred, although more difficult. The plants will re-sprout from remaining roots.

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      • tonytomeo says:

        We only cut them if we neglected to pull them for so long that they are going to seed. By that time, the roots would not likely come out intact by pulling anyway. Strangely, after cutting, almost none of the seed germinates. It is as if it must dry and blow away to be viable.

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