- 1). Identify the thistle species and determine its potential for harm. While thistles brought over from Europe, Asia and Africa can cause serious harm to a landscape, native thistles grow in harmony with the local environment and don't require intensive control measures. A wildflower field guide, local plant nursery or extension office can help you with thistle identification. Some invasives to watch out for include the scotch thistle, which can reach up to 8 feet in height with many flowers on each plant, and the musk thistle, which grows a single fuzzy flower that can reach 3 inches in diameter on a 6-foot stalk.
- 2). Mow lawns where thistles have invaded, cutting the plants down before the flowers begin to show color. You may need to mow repeatedly to keep the plants from regrowing.
- 3). Till or cultivate gardens where thistles have established themselves, before the plants form flowers and seeds.
- 4). Hand-pull or cut individual thistles you find in your garden. Remove them as close to the ground as possible to discourage regrowth.
- 5). Remove flowers and seed heads from any thistles that have blossomed and throw them in the trash or burn them.
- 6). Apply an approved herbicide if other control measures do not work. Since herbicide recommendations vary by area, change frequently and depend on the thistle species as well as nearby plantings, you will need to contact your local extension office to learn what products are safest and most effective for your particular circumstances. The label is the law -- always follow instructions and warnings on the label precisely to avoid harm to yourself, your lawn and garden and your local ecosystem.
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