There are several types of thistle that are commonly called star thistle. Many of these are not native to the U.S. such as the yellow star thistle, Canada thistle, bull thistle, Italian thistle and musk thistle. They are well known for taking over backyards, pastures, orchards and rangelands quickly; to the detriment of most other plants. Even more harmful is the yellow star thistle as it is toxic to horses. Eradication of star thistle must take a multimethod approach to be effective. A combination of or all of these steps can be used together.
Things You'll Need
- Tilling tools or equipment
- Goats or sheep
Remove as much thistle manually as you can. For a small backyard, you can dig up the thistle and hand-till the ground. For pastures and ranges, you can employ a herd of goats or sheep and till the ground with larger equipment.
Lay down 6 to 8 inches of mulch. This is best for small backyard areas to suppress the thistle regrowth once it has been removed. For yellow star thistle, pine shavings have been found by researchers at the San Luis Obispo County Agriculture Department to be very effective.
Plant a more appealing competitive plant. Clovers such as crimson or rose clover can be planted in pastures or rangelands to prevent invasive thistle.
Release beneficial insects. There are many insects that target thistle and ultimately kill the plant. You will need to know the exact species of thistle to determine which insect to release. For example the peacock fly targets yellow star thistle, the thistle-head weevil will eat several species of thistle, and the thistle-stem gall fly eats the stems of Canada thistle.
Apply an herbicide directly to the plants. Use an herbicide that his known to kill the species of thistle you are targeting with the least amount of toxins. BurnOut Weed & Grass Killer and Nature's Glory are some vinegar-based options.
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