Annual flowers must grow, bloom and produce seed all in a single growing season. Such an effort requires an enormous amount of energy. Most annual flowers need consistent moisture to perform their best. Gardeners in arid areas, however, can turn to a few drought-tolerant annuals that thrive on minimal moisture once established. These annuals bring color and form to the driest locations.
Indian blanket (Gaillardia pulchella) is a 1-to-2-foot high aster-family annual that grows wild in dry, open areas across much of the United States. Its branching stems have heavily leaved bases. From May to August, Indian blanket has colorful daisy-like blooms. The petals have yellow tips blending into red bases around red-brown centers. Plant Indian blanket in sun to partial shade and neutral (pH between 6.8 and 7.2), well-drained, infertile sandy soil. Plants in rich soil flower less. Deadheading---removing spent flower heads---will extend bloom.
Moss rose (Portuclaca grandiflora) is an annual ground cover native to South America. Standing up to reach 9 inches high and up to 1 foot wide, it blooms from early summer until first frost. Moss rose has clusters of 1-inch, grayish green, needle-like succulent leaves on creeping reddish green stems. Charming, 1-inch blooms----resembling miniature roses----may be white, yellow, orange, peach, pink or red. Bicolored cultivars with single, semi-double and double flowers are available, according to the Missouri Botanical Garden. Use drought-tolerant moss rose in those hot, dry infertile spots where little else will grow. It needs good drainage and full sun for maximum bloom. Flowers do not open on cloudy days.
Scarlet sage (Salvia coccinea) is a mint-family annual native to the southern United States from Florida to Texas, and to Hawaii. Hardy to 0 degrees F, scarlet sage is an upright, multiple-branched plant reaching from 3 to 4 feet high. It has small---less than 2 inches---oval green leaves on thin, reddish stems. From late spring until fall, according to the University of Florida Cooperative Extension Service, scarlet sage's stems have ascending pairs of bright red, pink or white tubular blooms. They are hummingbird magnets and excellent additions to cut flower arrangements. Use this heat-loving annual in mass plantings or borders. It likes part sun or part shade and grows well in sand, loam or clay. Space plants 2 to 3 feet apart.