Controlling pasture distaff thistle

Distaff thistle as well as  the other species of thistle are considered the most serious threat to range and pasture. Thick stands can completely crowd out other vegetation reducing grazing. The sharp spines can prevent access to both livestock and people. It is not able to be grazed due to the fact that it is unpalatable to livestock and wildlife. Once it is established it is very hard to get rid of because the seeds can survive for a very long time, some up to 8 years.

What is distaff thistle?

Distaff thistle is a fully erect plant that can grow up to 4 feet in height. All of the branches are on the upper two-thirds of the plant. The stems are rigid, ribbed, and white or pale green in color. Leaves on the stem are rigid ending in short spines. They posses a simple root system with an unbranched taproot with numerous fibrous secondary roots.

The flower heads are solitary and are about 1 to 2 inches in diameter surrounded with sharp spines. The petals on the flower are yellow with red veins which separates it from other thistles. They bloom from late spring into summer with seeds that are 1/4 in long and gray in color.

Distaff is a winter annual with seeds that will germinate when moisture becomes more available, being during the fall and early winter months. When the seeds fall off they generally do not travel very far so that will cause a very thick clump of them in a particular area.

This plant originates from the Mediterranean region of Europe and Central Europe. It was first reported in the U.S. in California during the late 1800s. It is believed to have come to Texas during the drought back in the 1950s when people brought in hay bales from California that had the seeds.

Controlling distaff thistle

The production and spread of it’s seeds must be stopped in order to get rid of the plant. Isolated plants can be killed with a herbicide or cutting it below the soil and removing it from the pasture. With the nature of this plant you can eliminate it with either Mechanical, Herbicide, and Management practices.

Mechanical

It is possible to kill this plant simply by mowing it but if done at the right time. You will want to mow the plant just before the flower bud formation stage. If you mow it too early then the plant will be able to regrow from the base and produce new flowers. If you wait till after it flowers then there may be enough food left in the stems for the seeds to mature and germinate. The main key to follow is to not allow the seeds to be able to make it to the soil and germinate.

Herbicide

There are several common broadleaf herbicides that can control distaff thistle. The one that was recommended to be by the NRCS here in Brady is Grazon P+D. As with mowing you will want to time spraying them in order to get the best result. In order to stop them from coming back you may want to establish a more palatable plant in that area to crowd them out.

Management

Distaff thistle generally take root in areas that have been heavily overgrazed. So one way that you can prevent them from even taking hold is to take steps to prevent overgrazing. This is especially true during the drier months of summer where your forages may not be so able to grow back,

Another step to take is if you are need to bring hay in from other places is to make sure that they do not have distaff thistle on their place otherwise you may just be bringing more seeds in.

Because of the hardiness of the plants seeds it may take 2 years or more to see the complete eradication of distaff thistle from your pastures.

Review

Distaff thistle is a very troublesome plant but can be eradicated or controlled using various methods

• Mechanical- must be sure to mow at the right time to get the best results
• Herbicide- Grazon P+D is a good overall herbicide for controlling this plant
• Management- Be sure not to overgraze your pastures and take steps to prevent the seeds from germinating

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