In the Garden:
Coastal and Tropical South
October, 2012
Regional Report

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With golden yellow color in a perfectly seasonal hue, yellow cestrum delivers the goods every year.

Tropical Garden Plants

There is an overlooked group of plants that we grow rather differently than gardeners in other zones. Lots of our favorites are hardy in the tropics but easily become seasonal perennials in subtropic gardens.

Nature and Nurture
A grower friend of mine once told me that the best thing about perennial plants is that if their current location proves unsuitable, you can move them the next year. The fact that they grow rapidly around here means that we divide them every three years on average and often move as often, almost as if they had wheels. I prefer to buy three of any perennial I have not grown before, plant in what I hope will be two successful sites, and keep the third in its pot as insurance.

Within a few weeks or months, the next step becomes obvious. Some of the plants that we grow as hardy tropicals or subtropic perennials are incredibly reliable, like batface cuphea and scarlet sage salvia. They bloom on in lousy soil or crowded containers as easily as in the best garden bed and readily return if set back by a frost inland.

A few, however, like the vase form of elephant ears, can rot in a very wet winter if planted too deep. And plants with thinner leaves, including some ferns, or with brittle stems, like those that sometimes appear on chocolate plants, can suffer damage from wind or salty air even if the temperatures are not a threat.

Make Smart Choices
The best strategy to keep these zone-straddling plants going strong is to grow them in their preferred microclimate. Longevity is extended, both during the season and over the years, and rebound will be weeks sooner. Look around your garden, noting which areas are sunny or shady, wet or dry. For example, you may find dry shade in areas under eaves, while the most exposed parts of the property may have full sun and dry soil. Irrigation can provide water to dry soils, but it is good to know if one bed stays damp or drains quickly.

Here are some of my favorite hardy tropical and subtropical perennials and the microclimates that best suit them.

Rubber plants, night blooming cereus, South American air plant, and every sort of snake plant are all good candidates for dry shade, areas of the garden that are not desert-like, but are more dry than moist. Unless the winter is very harsh, these plants will retain all or most of their leaves in the Southern Coasts region.

Where dry sun dominates, I like bottlebrush and gazania, and although flame-of-the-woods can tolerate some shade, its form and flowers will be finer in more sun with well-drained soil.

Cane and wax begonias, nun's orchid, chocolate plant, sultana (aka impatiens), and the darling shrub, yesterday, today, and tomorrow all thrive in damp shade. They tend to lose their leaves north of Orlando for only a few weeks if moderate conditions are maintained. If you allow their beds to dry out severely or sit in water, fewer will come back.

In wet shade, consider plants such as upright elephant ears, windowleaf (aka monstera), and the precious hidden ginger. Wet sun means a location in full sun with regular watering provided, with the opportunity to dry out slightly between irrigations. My ideal wet sun bed sports chenille plant, copper leaf, golden trumpet, summer snapdragon, angel trumpet, and night blooming jasmine.

Benefits of a Box Garden
As a three time knee surgery veteran, I know how important it is to limit the impact of gardening on bones and joints. But perhaps you want to garden without digging or simply add an architectural feature to an area. In all these cases, the solution can be to build a box garden.

The one I built for perennial plants is 30-plus feet long and 3 feet high and wide. Built of 2 x 6s and attached to 4 x 4 posts set in concrete, its sides are lined with landscape cloth that extends a few inches into the bottom of the box. Sturdy, yes, and I'm glad since it took a lot to fill it -- my well-composted pile of shredded hackberry tree about the size of a swing set, two pickup truck loads of planting soil from the nursery, ten large bags of ground pine bark mulch, and numerous odd pots of soil left over from this and that. This bed grows everything from angel trumpets to airplane plants and bananas. When a clump needs dividing, I dig it up and amend the soil before replanting to gain another three years of happy perennials.

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