A few months ago, I mentioned a technique that we use to clean milkweed seeds after harvest. We spread the fluffy seeds out on a concrete floor and light the thin pile on fire, burning the fluff off the seeds. It’s quick, easy, and fun. I learned of the technique from a fellow prairie restoration ecologist many years ago, and we’ve been using it ever since. I’ve also shared the idea with quite a few others.
Those of you who have either read this blog frequently or know me personally know that I am a strong advocate for experimenting with techniques whenever possible. In fact, I often reduce people to blank stares by blathering on about the importance of always testing restoration and other methods to be sure we’re using the most effective strategies. Surely, then, over the last decade or so that I’ve been using and advocating the “burn the fluff off” technique, I’ve followed my own advice and checked to make sure it actually works, right? Well…
…Funny story. Over the years, a few people have asked whether or not the heat from the fire might damage the seeds, ruining the germination rate. I’ve always had a standard answer. First the idea came from others, who had been using it for a while. In addition, the fire moves so quickly and our piles are so thin, the heat is almost surely be insignificant. Plus, these are prairie seeds, and are thus adapted to fires. Right?
When I mentioned the fluff burning technique on this blog, my friend James responded that he had actually tested the germination results after doing something similar and that the results from the burned seeds had been really bad. Surely, I thought, he must be doing it differently than I am. Probably his seed pile is too thick, making the heat intense enough to kill the seeds. Plus he tested it on a different milkweed species than I had.
But, I figured it’d be fun to run a test anyway, so I asked Mardell, who is in charge of our small greenhouse, to try it out. She planted a batch of seeds that we’d burned and a batch that we hadn’t. You can see the results in the photo below.
What did I learn from this? Always test my assumptions. (Where have I heard that before?)