PlantFiles: Canada Thistle, Creeping Thistle
Cirsium arvense

I have dealt with this plant my entire gardening life and continue to hate it. Every bit of root you leave behind when pulling them will sprout new growth and the harsh prickles that are on every stem and leaf will go into your gloves, shoes and socks making life miserable for you. It takes at least two sprayings of a broad leaf weed killer to kill the plant and you still have to come back in a couple of weeks to make sure that you have killed the plant. I have read that the seeds last 50 years in the soil and will grow when disturbed. The flowers will continue to go to seed after they have been removed from the roots. My sheep and goats hesitate to eat it since the spines are so sharp. This weed is on most US states noxious weed list and that is where it belongs in my opinion.

Thistle is the worst weed in our yard and garden. It grows so well here that I don't have to worry about depriving the wildlife by killing what's on my property. : )

I used to dislike wearing gloves for gardening, but thistle makes it necessary. My husband likes to use Roundup on them, but then it takes forever for them to die and you are left with the ugly, spiny plant material. I prefer to pull them, on a day after it has rained. More of the root will come up if the ground is moist. It can help to dig a bit of soil away so that you can grab the root itself.

We used a broadleaf weed herbicide on the lawn a couple of years ago, and it seemed to work pretty well.

These buggers even like the very dry, very shady north side of our house.

In the vegetable garden, we've taken to using black plastic as a mulch, and that keeps the thistle out pretty well.

I love the way these plants look, but had to eradicate a huge colony from ground I wanted for a new garden. The first year, I dug by hand with fair success - as noted, every little bit left resprouts. The second year I sprayed with white vinegar on a sunshiny day. Sunshine is a vital factor in the vinegar's success. Had to repeat the vinegar spray two or three times for some of the hardiest thistles, but definitely the easiest and most effective way. Now, the garden is lovely, but I do miss the thistle blooms - occasionally!

When it stays near the evergreens, I'm ok with it. I only hate it when it grows in the center of the yard and one of my kids steps on it. :-/

The flowers are pretty, and finches LOVE the seeds. It's cute to watch them sit atop one and nibble away - leaving the fluffly white part of the seeds trail away like clouds. :-)

The only time I see those little yellow guys is when these seeds set.

I hate Canda thistle! They can penerate gloves and are stubborn to remove, can pop up in bushes where removal is difficult. They also gets chewed up by bugs or are coarse. One way I have found to remove this species is by carefully grasping the bottom of the plant where it contact the ground - about a hand's height and then pull on it and keep a vigorous search for any resprouting. The spines is nearly nonexisting on this portion but you have to be careful - leaves can touch the hand. Bull thistle, the only other common weed thistle for the North US is best done in mechanically - even the bottom is very spindly. I have seen huge amounts of roadside covered in Canada thistle - usually in roadside where the soil have not been disturbed since Minnesota stopped mowing most of the roadside except a certain distance away from the road. [To clarify - I have seen road construction plow out pretty much every inch of roadside - after a few years when the weeds have settled down there are more native grasses like Little Bluestem with its reddish fall colors and perennials like False Sunflower (I have counted at least 3 to 4 species alone just on the roadside!) - in contract the nonplowed roadside often contain 99% monotype grasses along with Canada thistle and Field Goldenrod.]

This is such a pretty flower, and the plant is very useful to wildlife, so I leave these in the wilder parts of my garden.

This plant is listed on the North Dakota invasive/troublesome list and this information is being distributed in a guide developed by the ND Weed Control Association and other agencies.

Plant Features
Perennial, up to 4 feet tall
Shiny/waxy/spiny green leaves
Clusters of purplish to whitish flowers
Blooms June through August
Seed head, cotton-like tuft
Mid-spring emergence, plants may also emerge early fall in a rosette stage
Spreads by creeping roots (rhizomatous) and seeds
May form dense patches

Distribution
Widespread invasive that grows under most conditions

Interesting Facts:
Plants are either male or female (dioecious)
Butterflies, such as the Painted Lady, lay eggs and their larvae feed on plants.
The roots of a single plant can spread 20 feet laterally and reach depths of 8 feet
Day length of at least 14 hours is needed for the rosette to bolt and flower

considered noxious weed in western Canada. Extremely difficult to remove.

Canada thistle is only a problem in the northern part of the US and Canada. It has a very extensive root system that breaks easily, and every bit must be removed or it just increases. It grows readily in almost any soil, from dry through wetlands. The seed is so light-weight it can be blown far and wide. It remains viable for years.

The most effective way to remove it is by repeated cutting of foliage until the roots die from lack of nourishment. Chemicals usually must be applied repeatedly because of its very dense root system.