Tuesday, October 17, 2006

Flower Fest - C for Canada Thistle

C. Canada Thistle. Cirsium arvense. Creeping Thistle.

I was amazed by this delicate wildflower. It was only about an inch in height and even less in width. It was like a blur of color on the wet ground in Morrison, Colorado. Morrison is about 8000ft in altitude. As usual, I had no clue what I was taking a picture of. All I knew was that it was a small beautiful purple wildflower.

The roots of the Canada thistle can spread more than 15 feet horizontally and its roots may grow into the soil anywhere from 6 to 15 feet deep.

Unlike the Buffalo Bur which tosses its spiny seeds into the path of all that may trod that way, the Canada thistle a creeping perennial that reproduces from vegetative buds in its root system. Roots and shoots can give rise to new plants. That's not to say that it does not produce seeds.

I took the above picture towards the end of September on one of my walks in the Open Spaces of Louisville, Colorado. It looked like it was done flowering and already producing seed.

It can produce between 1000 to 1500 seeds per flowering shoot and seeds are responsible for long distance dispersal. The feathery pappus helps disperse the seeds. However it is known to fall off leaving the seed attached to the plant, requiring other modes of dispersal. Seedlings grow slower and are subject to competition from other weeds especially as they are not backed by an extensive root system. Nevertheless, its seed should not be underestimated as it can remain viable in the soil for 20 years. The deeper it is buried, the longer it is viable.

Canada thistle has spread throughout the US except the south-eastern region. In Colorado, it is found in the plains and foothills, flowering from July to September. And, yes, it is classified as a noxious weed.

References: Colorado State University Cooperative Extension, Guide to Colorado Wildflowers Vol 1 Plains & Foothills and Guide to Colorado Wildflowers Vol 2.

Flower Fest - the A-Z of FlowersThis is my entry for the letter C in the Flower Fest - the A - Z of Flowers.

Flower Fest is the brainchild of Nature & Me and Sree. Every two weeks, the focus will be on a letter of the English alphabet. The current letter is C. I am submitting photographs of flowers as my entries.

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1 introspections:

Sree October 18, 2006 4:48 AM  

Lovely post!The flower looks like a softer version of the chives!:) I loved the third snap!Great work Manisha!

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