OK, so we should talk about “safe minimums” for temperatures that our plants can be exposed to. If you’re navigating how to get your plants outside or into an unheated greenhouse, this stuff is important to know. This heavily relates back into the temperature tolerance of plants and it’s especially important if you’re going to flirt with putting your plants outside or into a greenhouse.
In our experimentation efforts, there’s “safe” temperatures and then there’s “they’ll still live” temperatures. If you want to play it safe, most plants should never be exposed to temperatures below about 40 degrees Fahrenheit. If you follow this, your plants will be just fine and there will be little, if any, risk.
The one major exception to this that we’ve found are with any kind of pepper. Peppers are just super sensitive to temperatures and do not like anything below 50 Fahrenheit. When exposed to low temperatures, peppers can experience a life long debilitation that will affect all future growth.
So, that’s safe. But, we can (and often do) go even lower. Most cold tolerant and frost tolerant plants will have no problems with temperatures dipping below freezing, easily into the high 20’s Fahrenheit. Frost sensitive plants can easily experience temperatures into the mid-30’s and still be just fine. Peppers, well, are still peppers.
When you exceed these temperatures, plants will start to experience cold stress. This usually isn’t immediately lethal, but it does start to impact the quality of our plants. Time exposure to these colder temperatures is also a major factor. Short exposures are no big deal, but hours hit harder.
What’s critical, of course, is that we avoid frost. This is the “real” enemy of young plants and it can be absolutely devastating. We’ll be digging into the topic of frost and how it develops soon. But, the important thing to know is that frost can develop anytime when temperatures are in the mid-30’s Fahrenheit and below.
Some of you may be thinking these temperatures are far lower than you’ve seen “recommended” elsewhere, with “safe” temperatures being in the 50’s or even 60’s. All we can say about this is these folks are not cold climate growers and probably have never actually tested anything lower. Given our exceptionally cold climate, we’ve had plenty of opportunity to explore “true” minimums!
