The frost-tender, showy plants most of us think of as geraniums, are actually not geraniums at all, but pelargoniums. True geraniums, also known as hardy geraniums or cranesbill, are hardy, sturdy plants that survive winter temperatures of minus 20 degrees F. These plants bloom for several weeks early to mid summer, and produce simple pink, purple, or white flowers. The foliage is small, rounded and deeply lobed. Some varieties have variegated foliage or foliage that turns red in the fall. These plants require little maintenance, other than occasionally watering them and pruning them back to remove dead leaves or promote new growth.
Prune back geraniums by half in mid-summer with scissors or pruners if the plant starts to look leggy. The plant will produce new, compact growth and more blossoms.
Remove any dead or diseased leaves and stems throughout the year. Cut back dead foliage after the first heavy frost or in the spring. Many gardeners wait until spring, since the dead leaves may act as a mulch. Cut all dead foliage to the ground.
Apply a 3- to 4-inch mulch to the base of the plant after the first frost. Mulches act as an insulating blanket for perennials and prevent damage to roots from contracting and expanding soils. Choose coarse mulches, such as shredded leaves or wood chip mulch, that allow oxygen to reach the plant’s roots, advises Colorado State University Extension. Avoid grass clippings or wet leaves that will form a slimy mat.
Plant hardy geraniums in full sun to partial shade, in borders or under trees. Divide the plant in early spring by digging up and replanting a small outer portion of the plant.