Oh, radicchio. One of the most surprisingly difficult plants we grow. It still astonishes me just how many years it took to learn how to grow this plant well. Radicchio is the plant that’s made me feel stupid, learn lessons over and over and has drawn a line in the sand over how it will and will not be grown.
If you’ve never pitted yourself against radicchio, consider this fair warning. Those beautiful red heads you buy at the grocery are nothing short of literal crop mastery. And there is no other way to get a nice, lovely bunching head of radicchio than mastering this plant. What you’re observing here is a radicchio plant that is in the process of heading. Which we’ll tell you is easier shown than done.
An outside observer, unfamiliar with what they’re looking at, will likely look at this and say, “You’re in a cold climate, growing greens. What’s the actual problem?” Well, our saga with this plant spans at least a decade.
For the first decade, we tried to grow radicchio using intensive gardening methods. We went through variety after variety, completely failing to produce a head each season. We could easily get leafy greens, but never anything that looked even close to what we know as radicchio. A nice, tightly bunched head that cuts a lot like a cabbage.
We played with intensive growing spacing requirements, fertilizer levels and types and even went so far as to track down and try commercial grade genetics. Attempt after attempt ended in complete failure. Honestly, I completely gave up on ever being able to grow radicchio. There’s been few challenges in gardening where I just throw in the towel and declare something unknowable or undoable. But, I did that with radicchio.
Until three fateful winters ago, when I found myself revisiting this reigning champion of crop failures. I had previously done the deep dive into the genetics of radicchio and I knew that it hailed from the Asteraceae family. Though you might think it’s a brassica, given its similarity to cabbage, it actually has more in common with Aster flowers than it does a cabbage.
At the same time, I was doing the deepest dive into problems with growing from seed that I’d done to date. A familiar, but somewhat obscure, topic popped up called allelopathy. Which, is essentially when a plant emits biochemicals that help it reduce nearby seed germination to reduce natural competition. Coincidentally, at this time, I also made the connection that sunflowers were one of these plants to produce this allelopathy phenomenon. And that was when the link clicked.
Guess what family sunflowers are in? Yeah, that’s right. The Asteraceae family. They’re basically giant freaking Asters. It was incredibly probable that radicchio also produced allelopathic biochemicals and would actively reduce nearby competition!
So, chess board set, our next move was to give our radicchio some space. Not just “a little more” space, but “you’re not ever gonna touch another plant for your entire life” space. Not one foot spacing, two entire feet of spacing between plants.
And bam, that’s the deal with radicchio. If it touches another plant (and especially another radicchio) during the growth stages, you will not get a radicchio head. It also gives us a way to demonstrate allelopathy in “real life” and make the concept more accessible. Radicchio actively try to reduce nearby competition (by laying flat as opposed to heading) as a mechanism to ensure their space in the world.
Gardening is hands down the most advanced topic I’ve pursued. There’s rabbit holes and then there’s stuff like this that takes a decade or more to fully understand, link and eventually crack. This ain’t the stuff you’ll read in books or websites. It’s the product of sheer determination and an insane amount of research into growing.
So, if something’s got you down this growing season? Bolster up and harden yourself! This effort will take you to the brink and well beyond!
