Weed of the Week: Prickly Lettuce (and Sow Thistle)

My nemesis

This weed has been driving me nuts all spring. It’s not one I’d seen a lot before this year, then — out of nowhere — it infested large sections of your backyard. Not only did it infest the yard, but I had a tough time figuring out even what it is.

After digging around on a lot of university websites and talking to people who know their weeds, I think it is prickly lettuce (Lactuca serriola). But a couple of people have also identified it as sow thistle (Sonchus arvensis L.), and it is certainly possible that I have some of each. The two weeds look remarkably similar — and they’re both trouble.

Note the spines along the leaf vein. (Click for a larger view)

Both weeds like prairie plantings (we’ve got those nearby) and make forays into home landscapes. Both of them have leaves that look like dandelions and both of them emit a white sap when cut. Prickly lettuce has spines on the back of its leaves (and many of those in my yard also have that), as you can see from the photo, which is why I think that’s what I have. The weeds spread both by seed and by rhizomes!

I also learned that if you have a big deluge of rain (say 2 inches in 12 hours), you can pull prickly lettuce with abandon. It is much easier to pull than dandelions, so last week, in between rain storms, I’ve been pulling the prickly lettuce like crazy. I’ve also added some grass patch to the especially infested areas and will likely be over-seeding this fall. However, I don’t expect this will be my last battle with prickly lettuce, or sow thistle, or whatever it is.

What weeds have you been battling this year?


3 thoughts on “Weed of the Week: Prickly Lettuce (and Sow Thistle)

  1. Oh, how I hate sow thistle. We’ve been battling it here for years, too. If only the roots weren’t so ‘delicate’ for it annoys me no end when pulling it out to have the flimsy root break off with the gentlest of handling. It is truly amazing how far and how fast the plant colonizes an area. I’d rather pull quack grass any day! Good luck with your battle, and rest assured, you’re not alone.

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