Tuesday, January 12, 2010

Abiotic Stress: Cold Weather Damage

Abiotic plant disorders are nonbiological factors, usually associated with the plant's environment, that affect plants adversely. Important environmental factors include temperature, moisture, soil pH, air quality, light regime, and plant nutrition. If one or more of these factors goes above or below the optimum range for a given plant species, plant growth might be abnormal or adversely affected. Abiotic disorders may also be caused by human activities, such as pesticide and fertilizer applications.

The biggest problem affecting plants growing in south Florida this month is COLD temperature. There are a lot of tropical plants in south Florida that can be severely damaged or killed by cold weather. Sometimes it doesn't even matter how cold the temperature gets, but the change in temperature that can be damaging. This even applies to watering with cold temperature on a hot day. The surface of a leaf in full sun can get very hot, so when you irrigate with water that is much colder (i.e. 40 degrees), the rapid change in temperature can damage plant cells. Refer to the previous blog post (i.e. mesophyll cell collapse) for further information.

Anytime there is a threat of cold weather in south Florida, one needs to take precautionary measures to protect subtropical and tropical plants from exposure. The easiest and likely most common way to guard landscape and garden plants against frost is to use some type of covering. Old blankets, sheets, towels and strips of plastic mulch all seem to work fine. When covering plants, drape them loosely and secure the covering to prevent it from blowing off. Rope ties and stakes, rocks, or bricks are items that can be used. Lighter material like plastics and sheets can be placed directly over the plants, but be careful with heavier covers that may crush plants due to the weight. It’s best to cover plants late in the afternoon or early evening before the onset of freezing temperatures and then to remove the covers late morning when the sun is out and the temperature is above freezing. Plants should be well watered the day before a frost or freezing temperature is predicted. Research has shown that wet soil holds more heat than soil that is dry. The best way to know what type of precautionary measure you should take for your plants is knowing their individual needs. The more you know the better off they will be.

Links to additional information on cold damage:

Cold Protection on ornamental plants:

Cold protection tool kit:

Low temperature damage to turf:

Cold protection methods:

What to do after a freeze:

Photos of cold damage: