Plants that can survive hot, dry summers can be especially valuable. Mexican heather (Cuphea hyssopifolia) is this type of plant. Sometimes called false heather because it's not a true heather, it's a native plant in parts of Mexico and Central America. Winter frost can damage the plant's foliage, but it usually recovers and grows again in spring.
Mexican heather is a small evergreen perennial that has a compact, bushy form and grows as a flat-topped, mounded plant about 2 feet tall and up to 3 feet wide. It has flat, feathery sprays of leaves that extend out from its main stems, with small flowers developing at leaf axils, or the points where each leaf attaches to a stem. The blossoms are usually purple or lavender, but some varieties have white or pink to magenta flowers. The flowers appear in spring and can last throughout the summer and into early fall.
Mexican heather grows outdoors year-round in U.S. Department of Agriculture plant hardiness zones 9 through 11. In the colder parts of its range, where sub-freezing temperatures can occur in winter, frost may cause the plant to die back to the ground. In most cases, a healthy plant regrows the following spring, but may not flower until late in summer, because it puts most of its energy into growing new stems and leaves during the earlier part of the season. An especially cold winter might damage its roots or kill the entire plant, but Mexican heather self-seeds readily, so new seedlings usually emerge in spring when the soil warms.
You can help a Mexican heather plant withstand cold weather in several ways. Adding a 4- to 6-inch-thick layer of mulch in fall can help protect its roots from cold and also prevent heaving of the plant from the ground during freeze-thaw cycles. Keeping the plant well-watered in fall also helps keep it healthy and can protect it from cold. If you live in a colder portion of its range, siting Mexican heather near a warm, south- or west-facing wall of a building can help it withstand cold, or you could plant it on a hillside, where cold air drains away to lower portions of the slope.
Mexican heather grows well in partial shade, especially in areas with strong summer sun. It can grow in full sun in regions with cooler summers, but strong light may lighten its leaf color. It is quite drought tolerant once established, but benefits from regular moisture during its first year or two. In cold-winter areas, the plant can be dug up and potted to over-winter indoors, and usually does well in an indoor spot near a south- or west-facing window until the following spring. You can propagate Mexican heather by taking short pieces from young stems and rooting them in moist sand or potting soil. Because of its tendency to self-seed, Mexican heather has some invasive potential and isn't a good choice for a naturalized area.