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Canada Thistle

This noxious perennial seems to thrive well in our Idaho soil and can be found growing from spring through fall. One thing about Canada thistle is that it can produce beautiful pinkish-purple flowers, but touching the leaves on this plant can be quite painful. As with most flowers, bees and butterflies are attracted to this plant.

Although the flowers are quite attractive, they produce an abundance of seeds (up to 5000 seeds per flower) that create even more thorny foliage. In addition to spreading from seed, Canada thistle will sprout more thistle from its massive rhizome root system which will extend away from the plant by approximately 12 to 15 feet and a depth of 5 to 5 feet. You can see from this fact that it is very difficult to control this plant once it gets established. With age, this upright growing plant can reach a height of around 4 feet.

As explained, it’s difficult to control Canada thistle. We have found that Ferti-lome “Decimate” works fairly well on this plant, however it takes repeated applications to get it under control. Keep in mind that “Ferti-lome Decimate” kills nearly all plants including annuals, perennials and many shrubs and young trees. Always read and follow directions found on the label of any chemical including this one prior to use. Avoid pulling Canada thistle, doing so only creates more plants from its aggressive root system.

Although controlling Canada thistle can be somewhat difficult, the best way of avoiding this plant and most other weeds is by creating a healthy lawn and landscape program. This includes fertilizing, watering and applying Ferti-lome humates and iron/sulfur to our soil. A healthy lawn seldom has but a few weeds growing.

As a final thought, get this perennial under control when you first see it growing. It’s much easier to control when it’s small and hasn’t had the opportunity to spread and establish an invasive root system. Controlling Canada thistle is typically a long-term commitment. All plants need some sunlight to develop and grow. By constantly clipping the plant to the ground will help in weakening the plant and eradicate it. Canada thistle is not poisonous in nature, but its prickly foliage is not fun to touch.

For more information on Canada thistle and many other weeds found growing in your lawn, stop by The Home & Garden Store in Boise. We are here to help you with all gardening problems.

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