|The Cactus Patch|
|THE NEWSLETTER OF THE BAKERSFIELD CACTUS & SUCCULENT SOCIETY|
|Volume 10 February 2007 Number 2|
|Cold Enough To Freeze Your Bud Off
by Linda Cooley
Well, the "Big Freeze" has come and gone. How did your plants fare? In this article we will explore ways to keep your plants safe from the cold. First of all, it might be instructive to compare our recent freezing weather to normal temperatures experienced in Bakersfield and to explore how often these temperatures can be expected. The 1998 and 1990 Big Freezes were more severe than our recent cold weather. During the 1998 freeze event, temperatures dropped to 19°F and the maximum temperatures were not as high as our recent freeze. In 1998. we were as much as 17°F below normal during the 11 day period when minimums were below freezing. We had 3 days when the average temp was below freezing. In January 2007, the average temps were higher, with higher minimums and maximums, although we still had 10 mornings in a row with below freezing temperatures. The coldest two days (the 12th and 13th) were 12 degrees below normal. For comparison, the average low temperatures in late December through mid-January are in the upper 30s. The record low for both months is 19°F.
Here at my place in east Bakersfield (not up in the higher areas, I live nearer to Hwy. 58....) on Saturday January 13, I recorded a low temperature of 23 degrees at 7 am. On Sunday, it was 22 degrees. Most information I have read or heard indicates that a lot of cold-sensitive plants start getting damaged at 28°F, so 22°F is dangerously cold!
I grow mostly aloes, about half of them in the ground and the rest in pots. Some always spend the winter inside, near a sunny window. Others have done just fine in their pots outside in a semi-protected area, for example, under a tree or near the house. The aloes I grow in the ground are mostly from areas of South Africa that have similar temperatures to Bakersfield.
They never shown any damage from a normal winter, and some of them survived the two previous Big Freezes of 1990 and 1998. But--they sure didn't look good afterward! This time I wanted to protect them so that they would still look great! I erected a "greenhouse" of 6-mil clear plastic over the entire planting bed, supporting it on bamboo poles that were about 2 ft high. The plastic went all the way to the ground on 3 sides and was tacked to a railway tie that borders the fourth side. On January 13th the temperature on top of the plastic was 24°F and the water droplets that had condensed on the inside of the plastic were frozen. I stuck the thermometer inside the greenhouse, halfway between the ground and the plastic and the temperature was 28°F, so that gave me 4 extra degrees of protection, which is enough to prevent most damage. On the ground inside the greenhouse it was 30°F. The water drops were not frozen inside the plastic near the ground.
I brought the potted plants onto the porch near the house. The temperature there dropped to 26 or so. Some of those plants were damaged; a couple of them were killed (kalanchoes, mostly). I had some damage to the leaves of a couple of potted aloes, and some flowering stalks were killed back. I also put some potted plants on a storage shed under my driveway awning, right next to the house, and the temperature there dropped to around 30. Most of those plants were fine, except the Epiphyllum I forgot to bring in! I'm not sure if it is going to make it or not.
Out in front I have some Aloe vera and another aloe (maybe A. saponaria?) I covered some of them with a sheet at the last minute (I didn't have anymore plastic!) and was surprised to see how much that kept them from being damaged. The uncovered plants show leaf tip damage for almost half their length.
The biggest damage to plants under the plastic greenhouse occurred where the leaves touched the plastic, so it is important to raise the plastic up above the leaves and then seal it against the ground, to prevent air movement in and out of the greenhouse. Clear plastic works well because it lets the sun in, which warms the ground. Then the ground re-radiates the heat out at night. From what I have read, this can be a significant amount of heat!
Information from the weather service:
BAKERSFIELD RECORDS TIED OR BROKEN IN JANUARY
The 1998 Big Freeze was more severe than our recent cold weather. During that freeze event, temperatures dropped to 19°F and the maximum temperatures were not as high. We were as much as 17°F below normal during the 11 day period when minimums were below freezing. We had 3 days when the average temp was below freezing. In January 2007, the average temps were higher, with higher minimums and maximums, although we still had 10 mornings in a row with below freezing temperatures. The coldest two days (the 12th and 13th) were 12 degrees below normal. For comparison, the average low temperatures in late December through mid-January are in the upper 30s. The record low for both months is 19°F.
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