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Tuesday, October 29, 2019
Desert Horticulture Podcast: Freeze Alert from the National Weather Service Now!
Listen to this podcast so you know how to protect your tender plants from freezing temps.
Protect Plants from Early Fall Freeze Now
October 29
There are some freezing temperatures projected by the National Weather Service for the Las Vegas Valley over the next few nights. Temperatures may drop as low as 28F in some lower parts of the valley. What makes this worse is that landscape plants are not prepared for freezing temps. They need time to prepare and progressively lower temps help them to do this. Sudden freezes are the worst and cause the most damage!
If this cold air is combined with wind in your spot it will make it worse. Wind can channel between buildings and picks up speed in those spots. Wind removes any heat that might linger around and helps drop temperatures to freezing. Skies with good cloud cover and no wind usually don't allow freezing temps if there is a threat. Look at the sky and cloud cover before you go to bed.
Bougainvillea, a tropical plant that loves the heat of the desert, will freeze at 32F. It just does. Other tropical plants that freeze like this are tomatoes, peppers, eggplant and most of the hot weather vegetables. Plants that still have flower buds may lose them. Flower buds are very sensitive to freezing temps. They are more susceptible to freezing temps as they get closer to opening. If you have plants like Camelias that are loaded with flower buds, they may drop. Citrus too. Make a mental note which plants have flower buds.
Never, never, never apply nitrogen fertilizers to plants that are tender after August 1. Nitrogen fertilizers push tender new growth that is more susceptible to freezes than phosphorus and potassium. This includes compost! No compost applied to freeze tender plants after July 1. The fertilizers contained in compost are slow release and last longer so stop applying them earlier in the year to tender plants.
Covering the plants with a freeze blanket or crop cover gives you about 5 degrees of protection. Thats all. Temperatures may get as low as 28F so freeze blankets or crop covers will work provided cold air does not get inside. So fasten them to the ground tightly to prevent wind and cold air from entering the inside. Apply them to plants when the ground is still warm in late afternoon. Don't wait until night because you are relying on heat from the ground to get captured under the frost blanket.
There are some freezing temperatures projected by the National Weather Service for the Las Vegas Valley over the next few nights. Temperatures may drop as low as 28F in some lower parts of the valley. What makes this worse is that landscape plants are not prepared for freezing temps. They need time to prepare and progressively lower temps help them to do this. Sudden freezes are the worst and cause the most damage!
Where are the Possible Problem Areas?
Any lower parts of the valley where cold air has no where to drain or if it does drain, it drains slowly. Think of water. Cold air settles into low spots or pockets. But we really dont know how cold it will get. The NWS is telling you this so you have time to prepare and they usually are very cautious in their predictions. |
| This bougainvillea froze back at the peak of its beauty |
Wind Makes it Worse
If this cold air is combined with wind in your spot it will make it worse. Wind can channel between buildings and picks up speed in those spots. Wind removes any heat that might linger around and helps drop temperatures to freezing. Skies with good cloud cover and no wind usually don't allow freezing temps if there is a threat. Look at the sky and cloud cover before you go to bed. |
| Cloud filled skies mean warmer temps on the ground. Cloudless skies mean a greater chance of freezing. |
Plants and Plant Parts That Might Freeze
Bougainvillea, a tropical plant that loves the heat of the desert, will freeze at 32F. It just does. Other tropical plants that freeze like this are tomatoes, peppers, eggplant and most of the hot weather vegetables. Plants that still have flower buds may lose them. Flower buds are very sensitive to freezing temps. They are more susceptible to freezing temps as they get closer to opening. If you have plants like Camelias that are loaded with flower buds, they may drop. Citrus too. Make a mental note which plants have flower buds. |
| Flower bud drop due to a light freeze and damage to the edges of new leaves are signs of a light freeze. |
Summer Fertilizing and Freezes
Never, never, never apply nitrogen fertilizers to plants that are tender after August 1. Nitrogen fertilizers push tender new growth that is more susceptible to freezes than phosphorus and potassium. This includes compost! No compost applied to freeze tender plants after July 1. The fertilizers contained in compost are slow release and last longer so stop applying them earlier in the year to tender plants. |
| Fertilizers with anything in the first number, nitrogen, should not be applied after August 1 to winter tender perennial plants. Vegetables are fine because you will pull those to plant Fall vegetables. |
Protect Tender Plants
Covering the plants with a freeze blanket or crop cover gives you about 5 degrees of protection. Thats all. Temperatures may get as low as 28F so freeze blankets or crop covers will work provided cold air does not get inside. So fasten them to the ground tightly to prevent wind and cold air from entering the inside. Apply them to plants when the ground is still warm in late afternoon. Don't wait until night because you are relying on heat from the ground to get captured under the frost blanket. |
| Crop covers or frost blankets give you about five degrees of protection. |
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