Weeds - Part 5: Thistles

Some thoughts on weeds at Common Ground Community Garden, Greenwood Lake

Sona Mason - September 2023

It's easy to identify a Thistle - just pull it out of the ground. It will bite back.

While there are many native American thistles, the ones you'll find in your garden will likely be invaders from Eurasia. One of the common "tells" of invasives is how they take over an area. Just one seeding can produce tens or hundreds the next year. The reason is that their "foreign" array of defense chemicals is too alien for native bugs to nosh on, bugs which could otherwise keep their population from exploding all over the garden, and further out. Thus these plants put out many white wispy seeds that float up on the smallest breezes and descend on your lawn, your flowerbed, veggie garden, and native meadows and forest edges.

The most common non-native thistles are the yellow-flowered sow thistle, lavender-flowered bull thistle and pink-flowered Canada thistle. Nothing to do with Canada - just a mistaken common name thing. Most thistles are easy to identify before flowering by their spiked leaves, so don't wait until flowering, remove them now. With gloves.