Frost and Freeze Protection & Mitigation
If freezing temperatures are predicted there are things we can do to mitigate damage to frost sensitive plants.
Covering plants with frost cloth (that is not touching the leaves) is probably the best solution but usually not feasible.
As weird as this may sound it is probably better to water during a freeze. The theory behind that is that the chemical reaction & movement of the water raises the temperature slightly and may help protect the plants. The new water on the leaves is also is washing off the frost. The water in the pipes is coming out warmer than the air (or it would be frozen in the pipe). It also is delaying the freeze in the leaves by creating another layer for the air to freeze before starting the freeze on the leaves and the chemical reaction of freezing actually raises the surface temperature temporarily. IF ICE FORMS ON THE PLANT OR SOIL THE IRRIGATION WATER MUST STAY ON OR BE TURNED BACK ON TO WASH OFF THE ICE.
The Plants are damaged when the cells in the leaves (and sometimes the stems and roots) freeze and expand and burst. Different plants have different tolerances as to how cold they will get before the cell burst. Often times the freeze will just hurt some outer layer of leaves, it’s usually when the stems freeze or a large portion of the plant freezes that the plant dies.
After the Frost – Damaged Plants
A lot of damaged plants may not be dead. The damage is often not as bad as initially perceived. IT IS IMPORTANT NOT TO PRUNE THE PLANTS UNTIL NEW GROWTH APPEARS IN SPRING. The old growth will help protect the plant from future frost. Pruning will stimulate new growth which is much more susceptible to frost than a “hardened off plant”. You also won’t know the extent of the damage and where to prune to until new growth appears.