Shade structures are built to house a collection of shade-loving plants, start seedlings and cuttings, or just to relax in. The most common and utilitarian shade structure today is often found in garden centers. It is composed of a pipe or post-and-beam frame with a shading material on the top and perhaps the sides. The material often used today is polypropylene shade cloth, a woven or knitted fabric that provides a measured amount of shade.
Before the 1980’s, lath houses were commonly seen, with the shade being provided by lath spaced a few inches apart to let light through. However, many types of cover can be used to provide shade, from cheesecloth and other fabrics to bamboo reeding or plants.
Polypropylene shade cloth is available in different percentages of shade, depending on the weave of the cloth. The more open weaves not only admit more light, they also let more breeze pass through, keeping them cooler in enclosures with sides. 30% shade cloth is used to protect full-sun plants from burning or overheating in areas with hot sun. A 50% cloth gives medium bright light, and is commonly used in commercial nurseries. Shade plants grow well under this cloth. High density cloth is often used to cover patios and skylights.
Polypropylene shade cloth does not rot or mildew. Good shade cloth should last from 5 to 10 years. It is available in knitted or woven fabrics. The knitted types do not unravel if cut. If you order shade cloth from a supplier, rather than buy it ready-cut, you can have the edges taped and grommetted, which makes it easier to install. Shade cloth is available without a pattern or with a pattern of opaque bars that cast shadows like lath. Lay this patterned fabric so the bars run in a north-south direction. As the sun moves across the sky from east to west, the bars of light and shadow travel across the plants.
Stretch the shade cloth tightly, avoiding sags. Rain water runs down the fibers to the low spots and drips there, causing washouts or puddles.
Many people still prefer the looks of a lath house. The lath can be laid as individual pieces. They are usually spaced about a lath-width apart, casting a 50% shade. Manufactured trellises are also available. The lath in them is laid in a crosshatch pattern.
Lay the lath with a north-south orientation. As the sun moves across the sky from east to west, the shadows of the lath will cross the plants, giving them short periods of sun alternated with short periods of shade. Lath that runs east-west allows the bars of sunlight to remain in one place as the sun moves, burning the plants.
An arbor is an open frame that supports vines; the vines make the shade. Wisteria, grapes, kiwi, jasmine, and ‘Mrs. Banks’ roses all make satisfactory arbor covers. Some vines, such as wisteria and grapes, become very heavy as they age, and require a substantial arbor for support.