Beira tronchuda is a hybrid version of couve tronchuda, the essential ingredient in the Portuguese soup caldo verde. (Burpee)
Contributor

It has been 10 years and a day since I last wrote about an obscure green vegetable I’d just grown called couve tronchuda. At that time I could find only one seed supplier: Redwood City Seeds. Now, it’s in at least half a dozen catalogues.

Couve tronchuda is a leafy brassica, popular in Portugal, and the basis of what’s been called the Portuguese national dish, caldo verde. Translated as “green broth,” it’s a soup containing onions, garlic, potatoes (sometimes mashed up), olive oil, a spicy Portuguese pork sausage called linguica and the leaves of couve tronchuda, torn into strips so thin that they resemble blades of grass. (Another way to do this is to roll up the leaves, then slice them crosswise with a sharp knife.)

If that mixture isn’t hearty enough for you, some chicken or beef stock could be added, and even some beans. But the greens are essential. Don’t have any couve tronchuda on hand? Try it with sliced collards, cabbage or kale. No linguica? Use any smoky, garlicky pork sausage, and toss in some paprika if it’s not spicy enough.

Like many brassicas, couve tronchuda has been hard to categorize. I’ve seen it sold as both Portuguese cabbage and Portuguese kale, and it’s often described as similar to collards. That’s fairly accurate, since the leaves are large and relatively flat. The centers are somewhat cupped and frilled but never form heads the way cabbages do. More recently, a hybrid called Beira is being offered. But no matter what you call it, you’ll appreciate couve tronchuda’s sweet, mild flavor and its ability to hold its shape when dropped into a soup, whether Portuguese or not.

Also noteworthy are its prominent white stems and ribs, which are a bit like those of the totally unrelated Swiss chard, but not as wide. These are more tender than kale ribs and can be used as a vegetable in their own right or chopped up and simmered in the soup.

The other thing that distinguishes couve tronchuda from other brassicas, which tend to be cool-weather crops, is its heat resistance. That may well be the reason for its recent popularity. So if you’ve had trouble finding greens to grow for summer use, this is a good one to try.

Give each plant plenty of room, as it may form a rosette three feet across. Outer leaves may be cut and used continuously while new ones grow at the center, so frequent plantings are not necessary. Still, I’d suggest setting out some transplants in spring as soon as the danger of frost has passed, for a late-spring or early-summer crop. See how long you can keep them going, then put in some fresh transplants to carry you into fall — and beyond, if the winter is mild. The plant will not hold up under heavy freezes the way kale will, but a sumptuous soup of it will certainly be welcome as the weather starts to turn crisp and stirring hot soup seems like just the right thing to do.

Damrosch is the author of “The Four Season Farm Gardener’s Cookbook.”