Cold Protection for Nursery Crops
Dewayne L. Ingram, Thomas Yeager, Rita L. Hummel
EDIS Publication - http://edis.ifas.ufl.edu/EP025

Cold Protection for Leatherleaf Ferns
Bob Stamps, Professor, UF/IFAS
EDIS Publication - http://edis.ifas.ufl.edu/EP027

Set Your Critical Temperature

Irrigation for Cold Protection

Essentially all commercial irrigation of leatherleaf fern is done using overhead irrigation systems that use impact sprinklers because these systems can be used to cold protect this subtropical crop during freezes. There are several methods and techniques that can be used to minimize the amount of water necessary for cold protecting this crop.


Frost protection impact sprinklers having faster rotation rates (2 to 3+ revolutions per minute [rpm]) than conventional impact sprinklers (1 rpm) have been shown to provide equivalent cold protection using about 50% less water than when using conventional sprinklers.

Dual Irrigation Systems

Shadehouses equipped with two irrigation systems, one to apply water to the shade cloth and one to apply water to the crop, can be used to decrease the amount of water needed to cold protect leatherleaf fern during freeze events and to reduce the amount of crop damage during advective freezes. The over-the-shade cloth irrigation system is run just long enough to wet the cloth sufficiently so that ice can form and seal the openings. Icing of the shade cloth reduces advective and radiational heat losses.

Determining When to Start/Stop Irrigation

During mild radiation freezes where temperatures drop slowly over the course of the night, growers can watch for the onset of frost formation on the crop and start irrigating when frost first starts to develop. An additional technique growers can employ is to monitor immature fronds and start irrigating when the tender exposed fronds at the top of the crop canopy first begin to stiffen up, but before ice forms that causes plant damage. Fronds located in the coldest parts of the fernery should be monitored. (See Additional Factors to Consider for another water-saving technique to use during mild, calm freeze events.)

During more severe freezes, irrigation water applications for cold protection should start when wet bulb temperatures in the shadehouse or hammock reach 34°F (1°C) and stop when wet bulb temperatures rise to that same temperature, or slightly higher if it is windy. Additional Factors to Consider

During moderate to severe freezes, irrigation water is usually applied continuously to the crop; however, intermittent water application can successfully be used to cold protect leatherleaf fern during mild radiation freezes when ambient temperatures stay in the upper 20s (above -3°C). Careful monitoring of leaf temperatures and/or leaf surfaces for unfrozen water can be used to determine when to apply additional irrigation water. As long as there is a significant amount of water on the foliage in the liquid state, additional water application is unnecessary. As the water turns to ice, heat energy is released. When the supply of liquid water on the foliage gets low due to ice formation, additional water is applied. This technique is most practical for growers with one fernery or only a few ferneries located near one another.

The complete document can be found at http://edis.ifas.ufl.edu/EP027

Windbreaks and shelterbelts

when used in conjunction with irrigation water, can be beneficial in reducing cold damage during windy (advective) freezes by reducing air movement. However, temperatures inside shadehouses (prior to being cold protected) are often colder than temperatures outside shadehouses during radiation freezes. Most freeze events in Florida are the radiation type where lack of air mixing is the problem. Under these calm conditions, windbreaks and shelterbelts can make the temperature inversions caused by the stagnant air movement worse. Therefore, windbreaks that can be opened and closed are preferred so that they can be left open as long as possible during radiation freezes and closed up prior to advective freezes.

Chilling Injury in Tropical Foliage Plants: I. Spathiphyllum
J. Chen, L. Qu, R. J. Henny, C. A. Robinson, R. D. Caldwell, Y. Huang
EDIS Publication - http://edis.ifas.ufl.edu/EP101

Chilling Injury in Tropical Foliage Plants: II. Aglaonema
Jianjun Chen, Richard W. Henley, Richard J. Henny, Russell D. Caldwell, and Cynthia A. Robinson
EDIS Publication - http://edis.ifas.ufl.edu/EP103

Cold Protection of Ornamental Plants
Dewayne L. Ingram and Thomas H. Yeager
EDIS Publication - http://edis.ifas.ufl.edu/MG025

Low Temperature Damage to Turf
L.E. Trenholm
EDIS Publication - http://edis.ifas.ufl.edu/LH067

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