Regional Gardening Reports :: National Gardening Association

In the Garden:
Coastal and Tropical South
August, 2011
Regional Report

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Achimenes, aka Japanese pansies, deliver velvety texture and abundant flowers in shade gardens.

Shade Gardening

A dear friend once bragged that she can garden every day, even in August. She is right, of course, since the temperature is always a few degrees lower in her shady garden and sunburn is seldom an issue.

Kinds of Shade
There are essentially three kinds of shade, each available in most mature gardens and equally valuable to its design. Deep shade rarely sees direct sunlight and its ecosystem thrives in low light. Most of the deep shade plants can also grow in more light, but their treasure is the ability to live well without it. For example, cast iron plant, southern shield and other ferns can take up to half a day of sun if ample irrigation is provided. In deep shade, they go right on growing but require much less water. Deep shade occurs directly under trees, under deep house eaves, and often between close-set houses such as zero lot line properties.

High shade happens under tree canopies and offers bright light, sometimes bright enough to grow a few herbs and vegetables. To many gardeners, including my friend, the high shade space is ideal. There is light all day, plenty to read a book or grow flowering shrubs like hydrangea and abelia. Perennials are often undaunted by high shade, and those such as purple coneflower and gayfeather seem to hold their color longer without broiling in the sun. Indeed, most plants labeled for full sun can grow well in our high shade gardens. Lawn grass cannot grow in deep shade, but can sometimes do well enough in high shade to create paths or throw rug size patches between trees.

Dappled shade shifts the available light as the sun moves over the garden. Some spaces will have nearly full sun at times and much less light at other points in the day. Careful plant selection will insure a compatible planting regardless of the light differences. For instance, if a few spots along a border are drenched in sun most of the day, plant a small ornamental grass in each one. Their presence will unify the border while it takes the direct sun that its companions could not.

Two other designations are commonly used to describe shade. Part-sun and part-shade seem to be used interchangeably on plant labels. While these distinctions can be confused and seem to describe the same setting, they are quite different. If a shady space is at one end of a spectrum and a sunny site is at the other, the semis are important gradations between those extremes. Plants that carry the part or semi-shade label can tolerate as much as 4 hours of bright light or dappled sun, but need protection from direct sunlight. Those designated as part or semi-sun can tolerate the same amount of direct sunlight unless heat stress becomes an issue. For this reason, it is wise to provide morning and early afternoon sun for this group with shade in the late afternoon.

Shady Combinations
Besides the amount of light in a garden spot, soil moisture is key to combining plants in the shade garden. Of course, you can provide or withhold water and build soils to alter the natural state of a particular area. But those decisions depend on the needs of the plants you choose. Plants grow best when water is managed in one of three ways. It is consistently available in soil that is rich with organic matter and kept damp at all times. Plants like Japanese pansy, African mask, and hidden ginger thrive in such moist, low light settings. They are not bog plants and unlike LA iris, canna, or papyrus, do not grow well with their roots actually in water.

More moderate conditions are provided when the soil is allowed to dry out slightly between irrigation cycles. Plants that thrive in these conditions include both cane type and wax begonias and shrubs like yesterday- today-and-tomorrow and even lady palm. Color can abound here in conditions perfect for caladium, impatiens, and Persian shield. Mulch such plantings, even in pots, but pull the mulch back to see if the soil surface looks dry before watering.

For the third circumstance, wait even longer between waterings, until the soil feels dry up to the first knuckle of your index finger. This is the province of some of the toughest, most beautiful plants we grow, including the many varieties of snake plant, dwarf schefflera, jade plant, and croton. Great drainage is essential for these plants. Water them well but not often.

Making Shade
It is not unusual to see lath structures or more formal screen houses, especially in the Tropics region. We use them to be able to grow shade loving plants where no shade exists and to moderate conditions near doorways and around patios. As average annual temperatures rise and average rainfall decreases or changes its patterns, more plants are subject to previously unknown stresses. A canopy of shade cloth or a latticework baffle may become the new trend in garden ornament as climate change progresses over the next decade.

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