This has been a good year for weeds and a bad year for wildfires. With so many weeds running rampant over Elko County, it should be difficult to pick one to write about but I obsess over Scotch thistle. My hatred especially grew this year when I found two growing on my property. The seed source was probably a thistle on a neighbor’s lot.
These tall thistles seem to be everywhere this summer. Thick stands of Scotch thistle can be seen on property managed by private individuals, city, county, highway, railroad and BLM.
Part of the problem is it is hard to miss Scotch thistle, a weed often growing five to six-feet high and five-feet wide. The numerous stems have wings carrying spines ¼-1/2” long. The leaves carry a thick mat of cotton-like or woolly hairs, giving them a gray-green appearance. The thistle flowers are purple.
Stands of Scotch thistle grow so thick no animal, and definitely no person, can enter. The ground beneath a thick stand is bare dirt since nothing else can grow there.
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It is also known as cotton thistle or woolly thistle, a native of Europe and eastern Asia and was probably brought to North America as an ornamental.
Scotch thistle is a biennial plant, meaning it typically lives two years. It spends the first year as a flat rosette of two-foot long, whitish, spiked leaves. During the second year, this rosette grows into the tall thistle plant. A thick stand of tall thistles is usually surrounded by numerous rosettes ready to expand the stand next year. A thick stand often has new thistles surrounding a central stand of last year’s, dead thistles.
To control this thistle requires a multi-year attack. The best way to stop Scotch thistle targets those first year rosettes. Breaking the tap root with a shovel kills the plant. Killing all rosettes means no tall thistles the next year. Goats will also eat rosettes and herbicides easily kill them.
The second year thistles must be attacked early in summer, before they flower and produce seeds. July is too late to control seed production since seeds have already matured and dropped. Removing tall thistles now may help the property owner feel better but it does nothing to stop the cycle of rosettes and more thistles. Spraying thistles already carrying flowers is also useless.
Before the flowers open, the thistles can be snipped and removed by someone wearing leather gloves, or cut with a shovel, or sprayed. I have heard of people who use tongs to grasp the flower heads with one gloved hand as they snip it off with the other. The flower heads must be removed, since just dropping them on the ground does not work. The seeds still develop and drop from the fallen head. These people drop the flower heads into a garbage bag, which is then carried away from the site.
The rosettes are the key to stopping this invasion. Next year, during late spring, I will be searching my property for rosettes to kill. I will need to do this for several years since seeds can lie dormant for several years in the soil.
The Scotch thistle is an important emblem of Scotland. A legend says it saved a group of sleeping Scottish warriors from a group of Norse warriors who attempted to sneak up on them. The cries of pain from the invaders as they crept through thistles alerted the Scots. Anyone standing next to a stand of Scotch thistle would have no problem believing this tale.