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Wednesday, Oct 01, 2014
Lifestyle Stories

Plants need time to get used to cold


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Q: Regarding your Jan. 5 article, “Timing your winter pruning can be tough,” it may have been useful to point out that some winter pruning could reduce the number of spring blooms you’ll get on gardenias, etc. Not quite sure, but I wonder if frost (32 degrees, ice crystals) may offer a bit of protection against freeze (sub-32 degrees) damage.

Answer: Comments are always welcome, thanks! One of my co-workers provided the following information.

On pruning gardenias: Pruning keeps plants shapely and in scale with the landscape. Pruning should be done just after the plant finishes blooming. In our area, that means that any major pruning of gardenias should be done in June and July. If heavily pruned at other times of the year, there is a great risk of removing, or preventing the formation of next year’s flowers.

Below is information from University of Florida IFAS publications and Louisiana State University regarding frost protection against freeze.

From The University of Florida IFAS: Winter temperatures in Florida are frequently low enough to cause cold injury to tropical, subtropical and occasionally temperate plants not adapted to Florida climatic conditions. Tropical plants and summer annuals do not adapt or harden to withstand temperatures below freezing, and many are injured by temperatures below 50 degrees. Subtropical plants can harden or acclimate (become accustomed to a new climate) to withstand freezing temperatures, and properly conditioned temperate plants can withstand temperatures substantially below freezing. The ability of plants to withstand freezing temperatures is affected by temperature fluctuations and day lengths prior to a freeze. A gradual decrease in temperature over a period of time increases the ability of plants or plant parts to withstand cold temperatures. A sudden decrease in temperature in late fall or early winter usually results in more damage than the same low temperature in January of February. Short durations of warmer temperatures in midwinter can deacclimate some plants, resulting in bud break or flowering. Deacclimated plants are more prone to freeze injury. Preconditioning of tropical plants to withstand chilling temperatures has not been well documented. Full article: http://indian.ifas.ufl .edu/hort/Cold_Protection _Orn_Plants.pdf

From Louisiana State University: Weather conditions prior to a freeze or frost also play a role in how these temperatures affect plants. If the first cold event is a freeze, landscape plants will suffer more damage. If several cold fronts move through the state and produce several frosts prior to a freeze, we will see less negative impact to plants that normally show damage.

Lynn Barber is the Florida Yards and Neighborhoods agent at Hillsborough Extension. Reach her at BarberL@hillsboroughcounty .org.

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