Freeze Protection of California Avocado Groves

As California transitions to winter months, growers are confronted with limited frost-protection options. Freeze damage can reduce spring flowering, so be aware of temperatures falling below 30-degrees Fahrenheit, regardless of weather forecasts. Rather than rely on forecasts, establish a frost management plan and follow it.

Avocado tree health is an optimal means of protecting trees from freezing conditions. Maintain optimal health as follows:

• Maintain consistent irrigation, as recovery time has proven shorter in blocks irrigated a few days before arrival of cold temperatures. Water-stressed trees are physiologically less capable of enduring freezing temperatures.
• Consider management factors and nitrogen deficiencies that reduce leaf canopies, as they can further erode avocado trees during a freeze.
• Reduce weeds surrounding the tree as they make the soil colder, restricting heat release from the ground during a freeze. Avocado groves have historically shown severe damage — or death — when weeds are abundant.
• Ensure trees are well nourished, as healthy trees recover faster.
• Maintain proper leaf-nitrogen levels to increase leaves’ tolerance to low temperatures and to develop thick-foliage cover, so outer leaves can protect inner leaves.
• Avoid severely pruned, top-worked and/or crowded trees
• Pay attention to the weather forecast.

If a freeze is predicted, act quickly to protect your trees. Irrigate a few days prior to a freeze in order to:

• Remove water stress, as this improves tolerance to low temperatures.
• Increase soil water, as this can release heat during a freeze.

Protection During a Freeze:

• Apply heat to the grove, via irrigation systems.
• Use a helicopter to push warm air form the inversion layer down into the groves.
• Use a wind machine at low speeds. This has historically provided adequate protection in citrus groves, which bear similar production traits to avocados.
• Use heat pots, where permitted. Do not use heat pots with dry mulch, as this is a potential fire hazard.