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Thorny Thistle Thievery & Testimony

Why, why, why are you here Mr. Thistle?

Ever look at something and be instantly triggered into anger or annoyance? Canada thistle provokes that for a lot of people. It’s prickly, it’s pushy, it gets a foot in the door and then takes over the place…and it wasn’t even invited!  Actually it was probably unintentionally invited. Thistle tends to inhabit environments that need rest and rejuvenation, like overused and depleted agricultural and rangelands. It sneaks into areas of disturbed soil, gardens, roadsides, mismanaged playground and sports fields, marshes, and even wet grasslands.

Canada Thistle with popping seed heads.

Canada thistle is a cool season perennial which spreads by seed and by creeping roots vegetatively. Undisturbed plants tend to become inactive during hot weather (July and August). Then new shoots emerge during September and survive into November. The growth on Canada thistle in late September and October helps restore its underground food reserves.

It is the extensive underground root system that may penetrate the soil to a depth of 10 feet or more and grow laterally 12 to 15 feet per year, that is both a blessing and a curse. Root buds occur randomly along the roots and initiate new shoots whenever environmental conditions are favorable. Root segments as small as 0.6 inch can initiate shoot growth and become established. All this aggressive growth of roots and plant material competes against desirable crops and native vegetation…and the cattle don’t care for it either. (This is the curse.) The benefits to this crazy underground root universe is that it helps to aerate hard compacted soil and increases biomass to restore and conserve topsoil from blowing away. Canada thistle has been cited in studies on phytoremediation of hydrocarbons in Lithuania.  For humans, thistles  generally help aid in the detoxification processes of the body, particularly the liver (often linked to the expression of anger).  Milk thistle is the most famous of them, but Cirsium arvense (Canada thistle) is a good substitute.  Pollen and nectar from this thistle is also an abundant source for bees and insects. (This would be the blessing and testimony!)

Two years underground growth of Canada Thistle from original one foot of root.

It has been said that the first step to healing is awareness.  If you’ve got Canada thistle, try to understand not only its’ thievery, but also what it may be trying to tell you. (Neglected soil? Compaction issues?  Toxin Smorgasbord?)  Then mindfully decide, what you do want in its’ place and what would be the highest good for the land & soil?  Desirable native plants and healthy, biodiverse soil is a good place to start, and know that it will take commitment and diligence on your part.

Three things to remember in tackling thistle: avoid letting plant go to seed, timing is key when applying an herbicide (go organic!), and don’t cut all the way to the ground level or pull the weed (it stimulates additional root bud shoots).  However, cutting high at 8-10 inches retains the chemicals in the stem (auxins) and fools the plant into thinking it is still producing flowers, so root bud development  is retarded.   Also, studies show that plants of that height are more susceptible to chemical damage and will translocate better to the roots. This is the time to apply an organic herbicide (containing acetic acid or clove oil) into the open stems. Adding a surfactant (to the organic herbicide) will aid greatly in sticking to leaf surfaces and allowing penetration to the roots.  The ideal time to treat is in the very early bud stage when food reserves are at their lowest point (early spring) and during the fall when the plant is storing sugars in its root system to get it through the winter.  If some thistle sprouts back next spring, hit them again with an organic herbicide, and be sure to plant desirable varieties that shade out any Canada thistle stragglers, and amend the soil with compost.  If you’ve got Canada thistle and don’t want to tackle it yourself…contact Ecoscape!

By Karina Zedalis (2017)