When we talk about cold hardiness, most grower’s interests are going to solidly land in the “food” spectrum of growing. But, one of the things we have observed is that the concept of cold hardiness also extends over into flowers as well.
You’ve probably observed that some flowers are simply not cold hardy at all. The slightest frost takes them out and they’re done. This might even describe the majority of them. But, just like with vegetables, some types of flowers can exhibit surprising degrees of cold tolerance.
Once such flower got my attention this year and that was Nicotiana. Despite multiple frosts and sub-freezing nights, our Nicotiana flowers are still well in bloom and holding out fairly strong. For the uninitiated, Nicotiana is more or less in the family of tobacco plants. It’s basically tobacco that is grown primarily for the purpose of flowers.
Given that tobacco is a massive agricultural crop worldwide, I wasn’t surprised to find a study where biologists investigated the cold tolerance of the crop. Curiously, it’s been determined that down to about 4C, tobacco produces physiological responses that are thought to protect the plant against those cooler temperatures. Below this temperature, it was observed the protections dropped off heavily, but those protections don’t just suddenly disappear, either. Optimal temperatures with no damage to the plant has been determined to be no lower than about 10C.
That kind of surprised me, if only because I’ve always thought of tobacco to be a “southern” crop. Thinking about it, though, that geographic preference is more about the longer nights in late fall, which promotes flowering and “finalizes” the maturity of the tobacco leaves. Tobacco is sensitive to photoperiodism, a topic that describes the physiological responses to greater periods of daylight or darkness.
Anyway, just a curious observation and rabbit hole that I found interesting. There’s lots of other flowers that feature degrees of cold tolerance as well. While it’s not optimal to wait until post frost for flower displays and arrangements, it is nice to have a few flowers that are hardy enough to make it into the cooler late season!