What most people think of as geraniums, the round-leaved red, white and pink flowering summer annuals, are actually Pelargoniums. True geraniums, also called "cranesbills" because of the shape of the seed head, belong to a genus of between 250 and 400 species of annual, bienniel and perennial plants. Geraniums are an underused group of easy-care plants with varieties that can grow from a petite 6 inches to over 30 inches in height. While often grown for their foliage, Geraniums also bear single and double flowers in pink, white, blue or lavender.
Bloodred Geranium (Geranium sanguineam), also called bloody cranesbill, is one of the oldest and most popular varieties. Its name comes from its deeply lobed leaves, which turn to deep red or maroon after the first hard frost. The most commonly grown true geranium in the United States, it is hardy from USDA zones 3 to 8. Bloodred geranium works well as a ground cover under shrubs such as viburnums or lilacs.
‘Johnson’s Blue’ is a hybrid of Geranium himalayense and Geranium pratense. It blooms in June in mounds of 15- to 18-inch tall bright blue, cup-shaped flowers. Like many of the cool-season blooming geraniums, it goes dormant in hot weather.
‘Black Beauty’ is a summer blooming variety with a 15-inch spread that produces purple flowers on an 8- to 10-inch tall mound. Grown mainly for its fall foliage, it is one of the best dark-leaved varieties available.
Geranium macrorrhizum ‘White Ness’
Originally found on the slopes of Mount Olympus, ‘White Ness’ bears pure white flowers with long, yellow-tipped stamens throughout the summer. It grows in mounds from 8 to 10 inches tall and 18 to 24 inches wide.