Heat Tolerant Greens: Varieties for the Hottest Summer Months
As our season slowly evolves from spring into summer, those of us who grow greens all season long are thinking about how to change up successions to those that will put up with heat. This is a challenge every year, as consumer demand for fresh leafy greens remains strong while it becomes increasingly difficult to produce quality greens without the bitter leaves and tough texture that say “mid-summer.”
Some greens are best left out of the hottest succession, mainly the spinach and the other super cool-loving greens, but fortunately there are others to take their place. As a general rule for specialty greens, the types that make a bigger frame as full-size plants will do better in the heat, i.e. resist rapid bolting, even as baby greens.
This group of large-framed types includes bigger-framed mustards like Green Wave and Golden Frill, the bigger-framed Asian types like Mizuna, Tat Soi, and Tokyo Bekana, and then a few that just happen to resist bolting, such as almost all of the arugulas. Of course baby kale and baby chard can also do well in heat (with enough water), as they won’t bolt without experiencing cold temperatures.
For lettuces, there are similar big differences in bolt resistance between varieties, though the differences do not have as much to do with frame size. Batavian (also called Summer Crisp or Crisphead) types are bred specifically for heat tolerance and will almost always hold better than other types. Their leaves tend to be a bit thicker and less refined than other types, but in the heat of summer their reliable bolt tolerance makes them our new best friend. And then, as with the greens, a few varieties stand out as having unusual heat tolerance for their class. Among these are Green Star green leaf, Coastal Star green romaine, New Red Fire red leaf, and Red Oak Leaf. All of these will generally hold longer as full size heads in the heat, meaning they can be left out when other varieties have to be harvested immediately or lost.
If any of these haven’t yet found a spot in your rotation, consider giving one or more a try this year!