Frost Protection Tips For Strawberries

Frost Protection Tips For Strawberries

A significant frost/freeze event is being predicted for Wednesday night-Thursday morning.  This has the potential to injure and kill susceptible strawberry flowers and buds that are now present in most strawberry fields.  Growers should be ready to protect their plants with irrigation and/or row covers. Check your pump, pipes and sprinkler heads to be sure that they are all in good working order and ready to use when the temperatures drop.

Critical temperatures at which injury will occur are as follows:

At tight bud: 25F
At the “popcorn”: stage 26F
At the open blossom stage: 30F
At green fruit: 28F

Monitor the temperature in the lowest part of your field; as this will be where the air is coldest, and start watering before the temperature drops to freezing.

At a minimum, apply water at 0.1 – 0.15 in/hr with a fast rotating head (1 cycle/min). Water must be applied continuously to be effective.  Under windy conditions, more water must be applied to assure adequate protection.

If the air is very dry (a low dewpoint), evaporative cooling will occur when water is first applied to the plants, actually lowering the air temperature, so irrigation must be started at a relatively warm temperature (see the table in the reference listed below). Most local weathermen can provide the current dewpoint, or it can be obtained from online weather information services.

Protection offered by row covers varies by thickness.  Thinner products may only offer 2-3 degrees of protection, while thicker covers can provide 4-6 degrees of protection. Put the covers on in the afternoon to collect some field heat prior to the freezing event.  Irrigation can be applied over row covers.  Place a thermometer under the covers to determine when to start irrigation.

For a good reference on frost control see this fact sheet from Cornell Cooperative Extension:

The Ontario Ministry of Agriculture Food and Rural Affairs also has a good frost control reference you can find here: