Defined on the USDA Plant Hardiness Map as a swath beginning in west Texas, covering most of the mid-south and ending in the mid-Atlantic states, temperatures in Zone 7 reach a minimum of 0 degrees F. This region experiences freezes but compared to northern states, has short, mild winters. Many azaleas, which are part of the Rhododendron family, are hardy in this region, are evergreen and bloom in mid-spring, according to the 1997 "Sunset National Garden Book." Azaleas thrive in acidic soil and most prefer partial sun.
Hardy in Zone 7 and some of the warmer parts of Zone 6, Gable hybrids include the bright pink Caroline Gable, purple Herbert and white Rose Greeley. Plants are compact, have dense foliage and glossy leaves, and are prolific bloomers. If planted in the coldest parts of Zone 7, Gable hybrids may lose some leaves during winter. Plant in partial sun and keep soil moist during growing season.
Glenn Dale Hybrids
Hardy in Zone 7 and developed specifically as cold-weather plants, Glenn Dale hybrids include the orange Anchorite, pale pink Aphrodite and white Glacier varieties. Some plants with bi-color blooms, including Geisha (white with red stripes) and Martha Hitchcock (magenta edged with white) are also available. These plants vary in look from tall and twiggy to low and compact, but most prefer partial sun and moist soil.
Though not bred for Zone 7 temperatures, Greenwood hybrids can survive temperatures down to 0 degrees F if kept wet. Varieties include the pink and purple Greenwood Rose, deep red Sherry and white Sleigh Bell. These plants are unique for their large, double bloom. Plant in partial sun in the coldest parts of Zone 7 and partial shade in warmer locations and keep moist, particularly when temperatures drop.
North Tisbury Hybrids
Best known for their late blooming season, the North Tisbury Hybrids include Pink Cascade, Red Fountain and Alexander, which has orange-red blooms and foliage that turns to a glossy bronze in the fall. These low plants spread, making them good candidates for ground cover and they don't bloom until mid-summer. In hanging baskets, these plants will cascade. Plant in partial sun and keep soil moist.