After our slightly crazy experience flaming sowthistle only to see it produce seedheads again and again, we decided to verify that we were not, in fact, crazy and flame in a more ordered fashion à la an experiment of sorts. So here’s what we did:
I picked some sowthistle (yellow flowers) and spread it out in the driveway.
Then I flamed it. I had Mike video part of the flaming but Audrey decided she didn’t like the flame weeder and so about 40 seconds in it sounds like somebody took a baby into a hot air balloon. Not much to see anyway except me blasting the sowthistle for a full two minutes. That’s a lot. Here’s how it looked:
And for good measure, here’s a close-up:
It’s pretty-well charred, right? Part of the issue in the first go-around, when the thistle kept producing seeds and we didn’t know why, is because we weren’t sure of the quality of our flaming. This time around, there was no doubt.
We waited about four hours before checking out the thistle again and, as we suspected, somehow seeds had survived that first round of flaming.
If you can’t see them in the photo above, try this photo. And if you still can’t see them, click on the photo for a larger version of it.
We flamed the sowthistle a second time and burned those fluffy seedheads to a crisp. I’m not going to keep posting pictures of partially-burned thistle because it pretty much looks the same, so here’s what happened: we had to flame the thistle four times before it stopped producing seedheads. Four times!
I did a little research after the fact and found out a couple of key facts. Turns out that sowthistle thrives after wildfires. You don’t say.
It also turns out that while flame weeding was the darling of organic farmers for a while, more recent research is demonstrating the limits of flaming, namely (1) it works best before seeding or (2) it works well early in the season on small broadleaf weeds; it doesn’t turn out to work so well on thistle or grasses. Next year, I’ll definitely use my flame weeder as a kind of pre-emergent herbicide before I plant my garden.
Those were the results for sowthistle: flaming not recommended. But what about Canada thistle? After all, sowthistle is relatively easy to pull whereas Canada thistle requires a strong back and cursing and still usually results in failure. Mike generously brought some Canada thistle flowers and buds to the driveway for me to flame in version two of our thistle-flaming experiment.
Surprisingly, it seemed to work!
Four hours after flaming, I took a look. Still burned.
The next morning I took another look. Still burned. Same story that evening.
I was ready to call flaming Canada thistle a successful strategy until I checked it one more time, a full 48 hours after initially flaming it. Result: seedheads. In other words, Canada thistle is even sneakier than sowthistle.
In light of these highly rigorous experiments, here’s what we’re going to do from now on: we’re going to forget the flamer when it comes to thistle and mow it or pull it in bloom. Flaming would require repeated applications, which is neither time- or cost-effective. Bummer.