With the temperature fluctuating up and down like it has, I have noticed a few things. Buds, both flower and leaf, starting to plump up.
This could be a good thing, Spring is coming early.
Or, it could also be a bad thing, the plants THINK it's Spring and a freeze will damage this flush of growth.
As long as a plant is dormant, very cold temperatures should not effect it. That is of course the plant is in a zone or so of it's normal range. Trying to grow Florida Anise in Canada may not be a good idea. I have mentioned before on this blog that Citrus can handle done to 28 degrees for a short period of time. As long as they have had a chance to go semi-dormant. Citrus really don't go fully dormant like a Maple for instance. They more or less acclimate themselves and brace for colder weather.
If the soil warms up and they flush new growth, that new growth is very susceptible to the cold.
These pictures are from some of my trees. I was pushing them along kind of hard with fertilizer and keeping them warm. We hit a low of 18 degrees and the heater in my hoop house couldn't keep up. The temperature only dropped to 30 degrees and this was the result:
The trees ended up being fine. I only lost about 3 inches on the tips of this one plant. It is a Cocktail Grapefruit. The overall effect was basically a little premature pruning.
Had I not been pushing it with fertilizer through the Winter, this would not have happened. I usually tend to push everything! This is why the general rule is, DON'T fertilize in Winter.
Well, back to my main point of this article. Flushes of new growth now.
If you are seeing new growth and also seeing Mr. Weatherperson predicting sub freezing temperatures, there are a couple of steps you can take. This will apply to any plant, not just Citrus.
Go up into Aunt Martha's attic and find a couple of sets of the old timey Christmas lights. You know, those great big ones that would melt your Christmas presents if they touched them. The new ones don't put off any heat, so they won't work.
Wrap a couple of strands around your plant and toss a sheet or plastic over it. Make sure you help prop it up with some wire cages or stakes so you don't break any branches off. You can also use a spotlight if you don't have the Christmas lights. You have just bought yourself a good 8-10 degrees. Just remember to remove the plastic in the morning so you don't have fried plant when the sun hits it.
Another idea, and this would take a little forethought. Get a couple of 55 gallon drums, metal or plastic, paint them black. Place a couple around your plant and fill with water. The barrel will absorb the sunlight and heat, and give it back throughout the night. The area will be a few degrees warmer and might be all you need to save your plant.
With a little effort, almost any plant can be grown anywhere. I still like container growing, but for those of you that want it all in the ground, I hope this gives you some ideas on how to....Use some protection!