Radiation frost is the most common type of frost we experience here in the Central Valley. It happens on clear cold nights when the air is cold and dry. Heat is lost from the earth’s surface into the atmosphere. Trees planted in open low areas that are exposed to winds are the most likely to suffer frost damage. That is because cold air tends to flow downhill and accumulate in depressions. The best place for citrus is near structures with a southwest exposure as these structures retain reflected heat.
Cold hardiness of citrus varieties depends on the citrus type. It is important to be aware of the cold tolerance of your particular type of citrus.
Steps that can be taken to protect citrus trees from frost damage:
1. Wrap tree trunk with insulating materials like frost cloth or cardboard. Plastic can keep these materials from getting wet, but alone is not much protection. Cover trunk from the ground to the lowest main branches.
2. “Cloud Cover” is a good protection device for the tree’s canopy.
3. The ground around tree should be moist and bare – this is because the soil is then able to radiate heat to the tree.
4. Holiday lights, 100 watt outdoor lamps, or freeze cloth can give some protection during a severe freeze.
5. This is not the time to fertilize or prune, especially if frost damage can be seen. Wait several months to assess damage – often trees recover during warmer months.
6. Wind machines are used commercially by mixing cold and warm air. They are not practical for the home orchard with only a few trees.
Master Gardeners are ready and waiting to answer your home gardening questions. Bring in any plant sample to help diagnose your garden problems.
Call the Master Gardener Helpline (559) 600-7224
Monday - Friday 9:00 a.m. to noon. Visit the UC Cooperative Extension office and ask for a Master Gardener. The UC Extension Office is located at 1720 S. Maple Ave, near the Fresno Fairgrounds, just south of Butler. Directions and Map to UCCE You can also send an e-mail to: email@example.com