Part of what makes my cold climate garden cold is the fact that we live in the bottom of a valley, and cold air flows downhill and settles all around us. So however cold the weatherman predicts it will get, it’s usually colder here. Often, ten degrees colder. For example, on May 12th, when a light frost was predicted, the low temp in the morning was 28F(-2C). The following morning, it was 28.5F (-1.9C). I call those two hard frosts. And on the 19th, it was 25.5F(-3.6C). When it gets that low, I call it a freeze. And I believe all these recordings were on the high side, because the temperature sensor is located near the house, under an overhang (it’s not supposed to get sopping wet), in the general neighborhood of where we are raising a bunch of chicks, using two heat lamps to keep them warm.
So, what happens when we get an untimely freeze like that? Well, it depends…
Same Genus, Different SpeciesI really don’t know what species or parentage these “trumpet” lilies are, but they are definitely the most frost tender lilies I have. Lilies only put out one set of leaves per year, so these plants are starting the growing season handicapped with less than a full complement of leaves. I don’t expect any blooms from them. I’ll be happy if they make it through another winter, and give me another chance.
When I removed the containers that I had put over these Oriental lilies to protect them from the freeze, I could see frost in between the leaf layers. But a week later, they still don’t look damaged. This surprised me, because I remember them getting damaged by frost in other years.
I didn’t realize the Lilium henryi bulbs had emerged, so never considered covering them, and they made it through just fine.
Protected in Vain?Plants from tropical climates have their limits when it comes to cold tolerance. Whatever temperature it was inside that upturned flower pot, it was still below freezing. However, keep in mind the insulating properties of soil. As a result of a timely comment, I was inspired by this post to pile more dirt over the tuber after I planted it. This protected it sufficiently that it was able to send up new growth. If the tuber itself had frozen, it would have died and no new growth would have been possible. Often in a cold climate, it pays to plant things a little deeper. Sometimes the most you can accomplish is reducing your losses. The more undamaged foliage there is, the more that foliage can feed the roots, building up the plant for a bigger, better display next year.
Continued in Part 2, where I illustrate how appearances can be deceiving, what happens to trees and shrubs, and a few plants unfazed by the dramatic temperature drop.