Thistle is the name used for a group of plants characterized by sharp prickles all over the plant including the stem and the flat parts of the leaves. Most thistles have stiff spines on the margins. Thistle can be biennial or perennial weeds with a variety of species primarily in the Asteraceae family.
The foliage on thistle can be as high as 12” and 4” wide. While thistle foliage may vary, common characteristics include spikey sharp points on leaves that can be painful to touch. The leaf margins on thistle are typically not entirely lobed but spines can occur along the leaf margins and the surface of the lower leaf may have hairs. Thistles usually have an alternate leaf pattern.
Thistles bloom in a variety of shades primarily pinks and purples. The flowers have a cone center with a single, spiny snowflake-shaped bloom extending from the stem and can be up to 1 1/3” high and wide.
Thistles have two different types of root systems. The spear thistle has a tap root and the creeping thistle’s root system grows on the extensive thistle rhizomes.
Treatment for Thistle:
A thistle is an annual weed that spreads by seed only. Typically, herbicides that are post-emergence are more effective. Fall (September through mid-October) and spring (late April through mid-June) are the best times to use herbicides when air temperatures are between 60 degrees and 85 degrees and when the weeds are actively growing.
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