In the Garden:
Persian shield can be kept alive through a mild winter in the lower south if mulched and provided with a cover on very cold nights.
Freeze Insurance for Semi-Tender Plants
We are fortunate to live in a mild zone where we can grow a number of plants not dependably hardy in most of the country. Stretching the zone is a favorite sport of gardeners. In order to keep these tropical and near-tropical plants through the winter, we need to provide them with a little protection.
There are many plants that are marginally hardy in our zone. Depending on where you live this may include various types of ginger, esperanza (Tecoma stans), firebush (Hamelia), red Bird of Paradise (Caesalpinia pulcherrima), Persian shield (Strobilanthes dyerianus), Philippine violet (Barleria cristata), and banana.
The above-ground parts of these plants will be killed by freezes, but we can take steps to protect the roots and basal crowns. Mound sawdust or compost around the base to hold in soil heat and protect during our brief freezing spells. Some gardeners place a wire ring around the plant and fill it with leaves. Then in spring they remove the wire and spread the leaves as a surface mulch. I generally cut these tender plants back after the first freeze and put them to bed for winter with a thick mound of mulch.
Semi-hardy fruit species like fig, Satsuma oranges, and kumquats need protection of their above-ground trunk and branches. Smaller species can be planted in a large container so they can be wheeled into a protected garage on a particularly cold night. If your plants are in the ground, an alternative is to mound up a large cone of loose, sandy soil around the base, reaching a foot or more high on the trunk. This will protect the graft union of citrus and therefore allow them to survive and re-establish if a severe cold snap kills the parts of the tree that are exposed above the protective mound of soil.
You may have seen plants covered with blankets on a cold night. This is an effective way to protect low-lying plants during a freeze. When covering plants before a freeze, drape the blanket or other covering over the plant before nightfall and weight it down to the soil. This will allow soil warmth to rise and help warm the plant's branches and leaves. Wrapping the top and tying the cover to the trunk creates landscape lollipops that won't benefit from this natural protective heat source.
When possible use cloth blankets or frost blanket fabric and cover these materials with plastic sheeting to prevent air movement. If plastic touches the plants, it can result in cold damage where it touches, so avoid laying plastic directly on the plants. But if plastic is all you have, go ahead and use it. The peripheral damage is a small price to pay for protecting the rest of the plant.
For an added measure of protection, place a source of heat beneath the protective cover. This could be a single incandescent light bulb or a string of the large outdoor Christmas lights. The heat they give off is enough to make a major difference on a cold night if the cover is secure so wind doesn't displace the heat with cold air.
Don't allow the light bulb to contact the trunk or branches of the plant as it can get hot enough to damage these tissues. Finally, take all necessary commonsense steps to prevent bare wires, shorts, plug connections, etc., from getting wet or from becoming a fire hazard with dry surface mulch.
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