Frost Protection Sprays

April 3, 2023

Plant health contributes significantly to frost resistance. In particular, frost resistance will improve naturally as plants develop more waxy leaves and produce higher levels of fat and lipids, all indicative of a high level of photosynthesis and sugar production.

There is another important piece: our understanding of how frost damages crops is that water gets into the interstitial space of the leaf, crystalizes, and then the sharp edges of the crystals turn the cell into mush.

So what are our options for frost protection? Obviously, get the plant as health as possible. But there are also several other options;

• Decrease the freezing temperatures: this method is similar to salting a road to keep it from freezing. In the case of plant production, urea is usually used, which is a non-organic salty form of nitrogen. Other products with potential would be potassium and SeaCrop, both salty by nature.
• Dry up the water in the interstitial space: when plants have high levels of pectin, the pectin will reduce or eliminate the free water in the interstitial space. This pectin layer is built by calcium, silica, and boron. We see the fastest response from foliar applications. With the right form of silica, a noticeable difference in leaf thickness and cell hardness can usually be noticed inside a week. In addition, it is important to understand that nitrate nitrogen can actually increase frost susceptibility because it triggers the plant to take up an excessive amount of water and triggers unhealthy, watery cells. So we could say that magnesium, sulfur, and molybdenum, the minerals needed to convert nitrates into proteins, are also important for frost protection.
• There are also several other nutrients that contribute to freeze resistance. These are manganese and copper. We don’t really know how it works but we know that they contribute.

So as you can see, there are many options and of course very little time to actually trial different products and rates. As a result, we have limited experience. I would say for non-organic options, 1-2 lbs. urea can make a big difference applied 1-2 days before a freeze event, along with calcium and silica. Organic options would be 3-5 lbs. Natural-Cal, which includes calcium and a protein form of nitrogen, along with 1-2 qt. Amino Blend, and 1 pound of Sil-Max for silica. Silica has long been known to increase freeze resistance. SeaCrop and SeaStim could be added if desired, as could copper and manganese depending on what you feel is most deficient. All rates are per acre, and we would like to see only 20-40 gallons of water as a carrier.

For strawberries, another really good option is water sprinkling. We start by covering up the plants with a floating row cover about April 1. Then we closely watch temperatures. Anytime the temperature drops beneath 32-33⁰ underneath the row covers, the sprinklers need to be started. If it is cold enough, the water will freeze on top of the row cover and create a tight insulation blanket and will likely save the blooms and buds. Remember that typical water is 45-50⁰, which helps bring heat to the berries even if it doesn’t freeze.