Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Our unseasonably warm March and April has lots of folks sitting on pins and needles. As we watch trees and shrubs continue to push new growth or get ready to push growth, the prospect of a killing frost looms like a big, dark cloud. Most trees and shrubs that have not yet broken bud should be able to handle temperatures into the mid-20’s without significant damage. Newly emerged growth, however, can be extremely tender and may be damaged just a few degrees below freezing. Nursery growers, and even landscapers and homeowners, may want to evaluate their options for frost protection. The two most common forms of frost protection for ornamentals and nursery crops are frost blankets and irrigation.
Frost blankets are one of the simplest and most effective forms of frost projection. Covering plants with lightweight fabric helps to trap radiant heat from the ground and prevent air temperatures from dropping below freezing. Some key considerations for using frost fabrics: Use light-colored, woven or non-woven materials that can breathe. Avoid dark-colors and impermeable materials. Remove frost blankets as soon as temperatures rise above freezing; heat can build quickly under covers once the sun comes out. Make sure frost blankets are held securely in place in case the wind should pick up.
Irrigation can be used for frost protection in many horticultural settings. Irrigation can protect plants from frost damage since a small amount of heat is released as water changes from liquid to solid. Because of this, it is essential that irrigation is run consistently throughout the freeze event to provide protection so that new ice is constantly formed. Irrigation should be discontinued once temperatures rise back above freezing. For an excellent discussion of irrigation for frost protection, see Chapter 12 – “Irrigation of Forest Tree Nurseries” in the Forest Nursery Manual: http://www.rngr.net/publications/fnm
Dr. Cregg's work is funded in part by MSU's AgBioResearch.