In the Garden:
Middle South
July, 2007
Regional Report

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Columbines like this one thrive in part sun.

A Shady Proposition

One sunny spring day a few years ago I planted rudbeckias, purple coneflowers, and climbing roses along a rail fence. I imagined rose canes heavy with flowers arching over the lush and colorful perennials. This year, I planted shade-loving impatiens between the struggling plants. What happened?

The planting area -- so sunny on that spring day -- gets a few hours of morning sun now but is shaded the rest of the day. In spring, the sun is lower in the sky so it reaches places it won't reach in midsummer. Trees that didn't cast much of a shadow in spring cast dark ones now. That spring planting was simply an error in judgment. I wasn't thinking about the future, just enjoying the warm breeze on a sunny spring day. The lesson? Before choosing plants for a garden, evaluate the bed to see how much sun it gets at different times during the day -- especially now, during the peak of the growing season. The bed along that fence is suited to "part sun" plants, not roses and rudbeckias.

What is Part Sun?
Many plants are described as being good for planting in part sun (or part shade). In warm, sunny regions like ours, it's important to know not only how many hours of sun per day a plant receives, but also when the plant gets that sun.

Morning sun. Perfect for many part-sun plants, morning sun warms the air and dries the dew on foliage. Because mornings are cooler than afternoons, direct sun in the morning is less stressful for plants than direct sun later in the day. Most plants labeled for shade will also do well with some early morning sun.

Midday sun. A few hours of direct sun in midday is enough to cook some part-sun plants. High air temperatures combined with the full force of the sun taxes plants' internal cooling systems. If you can fry an egg on the sidewalk, think of what the poor plants are going through! If you have an otherwise shaded spot that receives a few hours of direct sun in midday, look for plants labeled for "full to part sun."

Late afternoon and evening sun. As the day winds down and the sun drops in the sky, the intensity of the sunlight decreases. Most part-sun plants will do fine with some direct late afternoon sun. Some shade plants will tolerate an hour or two of sun late in the day as long as it comes as the air temperatures are dropping.

Dappled shade. Trees with delicate foliage cast dappled shade. Light is intermittent but doesn't hit the ground at full force, at least not for long. This situation is ideal for part-sun plants and even many shade plants.

Increasing Sunlight
You can increase the amount of sun reaching your garden beds by pruning lower branches and/or thinning the crowns of trees that are casting deep shade. Also, light-colored siding or walls reflect light, so painting a garden shed white, for example, will reflect light back onto nearby plants.

Make Your Own Shade
Do you need more shade for the plants you want to grow? You can start by planting appropriate trees and shrubs, but these may take years to reach a size large enough to cast the shade you want. In the interim, you have a few options.

Install a pergola. A pergola is a structure made up of upright posts supporting horizontal cross beams or sturdy lattice. Pergolas are frequently planted with woody vines, such as wisteria or grapes, and are often used to shade a walkway or seating area. However, they can also be used to cast shade on a garden. The amount of shade will depend on the type and pattern of cross beams or lattice and whether or not they are covered with vines.

Add a fence. A tall fence will cast some shade on its north side. In summer, when the sun is high in the sky, the shade will be limited to the area nearest the fence.

Use shade cloth. Commercial growers use shade cloth to shield sensitive plants from the midday sun. Shade cloth is woven or knit in patterns to cast various degrees of shade ranging from 30 to 90 percent. A large shade cloth awning on the south or west side of a house will cast shade on the plants below, help keep the house cool, and make a nice spot for a garden bench.

Don't make the same mistake I made and plant sun-lovers in a shady area. Otherwise, you may spend your next Fourth of July holiday renovating the bed, like I did. Take the time to evaluate your landscape at different times of the day and take notes on how many hours of sun each area gets, and when. When this time rolls around next summer, you'll be able to sit back and sip lemonade with the rest of the crowd.


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