Because of our recent rain, the wildflowers on roadsides, fields and meadows have bloomed, and I have enjoyed their colors while identifying them. However, there is one I constantly fight and will never appreciate.

From the asteraceae family and originating from Europe, Canada thistle (Cirsium arvense) is my least favorite of all wildflowers. With pale, lilac clustered flowers, measuring 0.5 inches to 0.75 inches across, this multi-branched plant can grow between 1 to 5 feet tall from deeply creeping roots.

With pointed, purplish bracts, this weed can adapt to any type of soil conditions, remaining unfazed by mowing or plowing. Difficult to control, it can withstand grazing, burning and herbicides. Management is not only difficult, but also nearly impossible.

Pronounced growth comes in June. During hot summer months, undisturbed plants are inactive, but with cooler temperatures, new shoots will emerge and can survive well into November. At this time, underground food reserves will ensure survival. Rhizomes and horizontal roots deep in the soil provide stored food, and buds on these roots, 6 to 15 feet deep, are stimulated when new shoots are removed. Digging out the thistle in my garden probably just prunes the plant, encouraging new growth. Using herbicides will not reach extremely deep roots and should be avoided in any garden. Knowing they do not grow well in shade, I laid black paper next to my back fence only to discover this persistent plant emerging 2 feet beyond the edge of the paper.

It is frost-sensitive, but the roots remain dormant throughout winter. Dry weather over an extended time also will prevent Canada thistle from spreading.

Pollination by honeybees and other insects is necessary since they cannot self-pollinate. In addition to deeply spreading roots, these dioecious plants (separate male and female plants), must grow in proximity for reproduction. According to Cornell University, seed production can vary between none to 5,000 seeds, depending on pollination. Their research has estimated that one single plant produced 26 above ground shoots, 154 underground shoots and spread 364 feet of roots, which penetrated 4 to 7 feet in two years, and covered 538 feet.

On a more positive note, goldfinches and other birds feed on the seeds of Canada thistle. While numerous insects can damage the plant, including the larvae of the painted lady butterfly which may defoliate it, these pests typically cause little lasting harm due to the thistle’s deep and resilient root system.

I plan to continue to declare war on Canada thistle, even with its painful prickly stems, to maintain my preferred perennial flowers, but I know this war will never end!

Kane Shipka is an Ohio State University Extension Master Gardener Volunteer in Mahoning County.