After this winter I learned a lot about overwintering tropicals. The most important one was that it usually isn't the hard freeze that kills plants but rather the constant cold temperatures, dry winds, drought and disease making a bad situation worse. Here are some more tips that go beyond the obvious protection measures.
1. Pay Attention to the Watering Needs
Although succulents and bromeliads like to be kept on the dry side, many plants are left without water when they need it most. When plant's cells are ruptured by frost, water evaporates from the damaged leaves quickly which means that you have to keep them hydrated enough to heal. Here in Florida its rather dry in winter too, so plants that would otherwise survive a freeze are often forgotten and die of drought. You don't need to overdo it, just make sure you don't forgo watering entirely during winter and spring!
Plants are much more susceptible to rotting in cold weather, so thoroughly clean your pruning shears between plants when taking care of the cold damage. I even found cold hardy palms that suffered from rot transferred after pruning rotting tender palms. Even if there's no visible cold damage, try spraying a fungicide around the crowns of your palms.
3. Temporary Mulch.
Although all you need is a light covering of mulch ordinarily, in winter it doesn't hurt to mound up some mulch at the base of your more tender shrubs and perennials in the coldest weather, spreading it back out afterward. This prevents subsequent disease by providing air circulation. Light and fluffy pine straw works wonders on smaller perrenials, and even kept christmas cactus, prayer plant and rubber ficus going through the winter. You can even stuff the crown of your bromeliads, tree ferns or philodendrons on the coldest nights!
4. Pick Root Hardy Plants
Gingers, and elephant ears are the easiest solution since they naturally store their energy in enlarged fleshy rhizomes, practically leaping back out of the ground in early spring! There is a huge selection of unusual choices, but my picks are crinums, blood lily, alpinias, alocasias and plain old lily of the nile. Many of these will actually retain foliage in winter, but their huge and cold tolerant tubers will give you peace of mind.
5. Plant Densely
I know that all the books tell you to give plants plenty of room, but if you're experimenting with tropicals I've found its best to pack them in nice and snug. This gives a lot more frost protection, and also keeps the cold winds from drying out the foliage.
For example, my shell gingers (alpinia zerumbet "variegated) were younger plants spread out with space between them. After this winter all that was left above ground were several stalks that remained protected by the taller ones. Just a few miles away is a shopping center that retained shell gingers up to 6 feet tall, all because the more mature specimens were tightly packed. Only the tallest stalks were damaged!
Here is my list of how everything did, updated today!
Hardiness List and Damage Report