Freeze damage can happen with frost cloths


Published: Wednesday, January 9, 2008 at 6:01 a.m.
Last Modified: Wednesday, January 9, 2008 at 12:00 a.m.

Q: Many of my tender plants were burned in the past freeze; it was like the leaves just melted even though I covered my plants with frost cloth. Why did they freeze under the covers, and what should I do now?

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Freeze damage on plumbago.

Special to The Sun

A: We haven't had a real hard freeze in Gainesville for a few years and many of the tropical and tender plants have been sneaking through the mild winters. Last week's freeze put an end to the tropical fiesta that the more tender plants had been enjoying. The freezing temperatures were accompanied by windy conditions, the wind made it hard for the frost cloths to stay on. That is why some plants got burned.

Gainesville was below 32 degrees for more than 12 hours the night of the hard freeze. The FAWN weather station near Turkey Creek reported 31 degrees at 7:30 the evening of Jan. 2. The temperature didn't rise above freezing until 10 a.m. the following morning. The weather station reached a low temperature of 18 degrees at 7 a.m. on Jan. 3. If you would like to see the data from the weather station you can access it at http://fawn.ifas.ufl.edu.

The prolonged time below freezing is also why you had damage under your frost cloth. Frost cloth is meant to trap warm air under the cloth. The warmth can dissipate when temperatures are so low for so long. Next time you can try putting a light under the frost protection to add warmth. Plants like plumbago, pentas, ferns, salvias and lantana will return from the roots when it warms up in the spring. If possible, restrain the urge to prune all the dead leaves and stems away, until the plant begins to push new growth in the spring. You do this for two reasons: the first is to ensure that you are not cutting off any live material. The second is because the dead stems and leaves may serve to insulate the crown of the plant from further damage. If your plants are in a high-maintenance area like a front walk or close to an entrance and you just cannot deal with dead sticks, you can remove some of the dead material, but try to be conservative in your pruning.

Q: I had a large vine come up in my backyard. It looked interesting, so I let it go, even though I didn't know what it was. It has grown quite a lot, and now it is producing beans that are 10 inches long and at least 1 1/2 wide. What is this plant, and can I eat the beans?

A: You didn't happen to trade your cow for a handful of the beans did you? I joke because I think the vine that took over your backyard is nicknamed the Jack bean.

There are a couple of beans that could fit your description that belong to the genus Canavalia. They are also called sword bean, chicksaw lima bean and Brazilian broad bean. The pods of these beans can reach lengths of 10 to 14 inches. The seeds inside the pod are large at 1/2 to 3/4 inch long. The Jack beans can be white seeded with a black seed scar about 1/3 of the length of the seed. Sword beans have red to pink seeds with a longer seed scar.

The vines will grow and grow, but not quite reach up to the sky. One Florida gardener reported that the vine took up close to 400 square feet of garden space.

Unfortunately Jack beans are only truly edible when the pods are very small and tender. Once they get to the size that you have now they are difficult to prepare and mildly toxic in large quantities.

Wendy Wilber is environmental horticulture agent for Alachua County IFAS Extension Service. Contact her via e-mail at WLWilber@ifas.ufl.edu.

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