Thistle: How to Identify and Control It

Weed maintenance is a central aspect of lawn care. If left untreated, weeds can overrun other plants, causing one's lawn to lose value. When controlling lawn weeds, it's important to identify the type of weed you're facing. This will help you choose the correct herbicide needed to rid your lawn of intrusive weeds.

What type of weed is thistle?

Thistle belongs to a larger class of plants called broadleaf weeds. This plant class includes trees and non-grasslike plants. Although broadleaf weeds are known for their wide leaves, thistle is identified by its colorful flowers or prickly leaves.

Thistle can be classified as either native or non-native. Native thistles are not as problematic as non-native thistles because they're less aggressive, causing little or no damage to other plants. On the other hand, non-native thistles, like bull and Canada thistle, can be destructive. Unlike native thistles, non-native thistles take vital nutrients away from other plants, rendering the land useless. This intrusive plant populates pastures, roadsides, rangelands, and uncultivated lands.

Thistles are either perennial or biennial. While biennial thistle lives for two years, perennial thistle can remain intact for more than 2 years. This is because biennial plants spread through seeds, and perennial plants spread using seeds and roots. For this reason, it's more difficult to rid your property of perennial thistle than it is biennial thistle. If not controlled, perennial thistle can cause long-term damage to one's lawn. To get rid of perennial thistle, you will need a more aggressive form of treatment.

How to identify thistle

Relatively easy to spot, thistle is identified by its flowers or leaves. Flower thistles vary in height; however, they commonly feature bright, pink or purple flowers. This type of thistle flourishes in overused areas. Experts recommend getting rid of flower thistle before its flower blooms. This is because seeds begin to spread soon after. Thistle leaves, like bull thistle, are generally prickly with prominent veins. This type of thistle is low-growing during the first year.


Before selecting herbicide, determine whether the thistle is 1) native or non-native and 2) biennial or perennial. This will help you choose the most effective form of treatment. For instance, if you're dealing with a native thistle, no treatment is required because the plant doesn't damage other crops or plants. However, if you have a non-native biennial or perennial thistle, you will need to use some form of herbicide. Since non-native biennial thistle's seeds spread above ground, it's important to keep existing thistle under control. You can do this by using a broadleaf weed herbicide that kills the plant.

Since a non-native perennial plant can spread using seeds or roots, you must cut the plant down before it has a chance to spread seeds or kill it using a broadleaf herbicide. In addition to destroying the plant, you must also dig up any roots to prevent the plant from taking over your property. You can purchase broadleaf weed killer in either granule or spray form. Keep in mind that broadleaf killer can spread easily, so it's important to keep children and pets away from the treated lawn for a few days after using the herbicide.

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