Besides geranium species growing in the wild, there are countless cultivars — plants that have been produced by selective breeding. Parer’s book describes more than 140 types suitable for gardens, but one in particular, Geranium ‘Rozanne’ has sold more than 6 million plants as of 2016 and is one of the most widely planted.
“I just came back from England in June and brought 71 (different) geraniums back,” Parer said. “I must be sick. I spent two days in a barn in Wales with friends, washing the roots of the plants for shipping back.”
Geraniums charm homeowners and landscape designers with their lengthy flowering period — as much as five weeks or more, which is exceptionally long for any perennial. Some geraniums put out a flush of bloom in the spring and then flower sporadically during summer. Others offer scarlet or brilliant red leaves in the fall. Depending on the cultivar, they can range in height from 6 to 24 inches.
Most geraniums tend to do best with morning sun and afternoon shade. Others thrive in full sun. Provide them with a free-draining soil enriched with compost and keep them watered, especially during drought, and they’ll be off to a great start. Once they’re established, little maintenance is needed. Geraniums also tolerate a wide range of soils, but they don’t like growing in low areas during winter where the water can collect around the roots.
At the Chicago Botanic Garden in Glencoe, there are about 80 different geraniums currently represented in the garden’s collections. Jacob Burns is curator of herbaceous perennial plants there. “Geraniums are an important collection because they’re a favorite landscape plant and they have multiple attributes,” he said. He has developed a detailed list of 180 different geraniums for the garden’s collection, which has the largest number of geranium types in the United States. Pressed to name a favorite, Burns says, “For unique flower color, I like Geranium phaeum. It’s an underused species with dark purple flowers — almost black.”
Geraniums can be used in a foundation planting, under trees or with shrubs and other perennials. Their finely cut leaves show off to great advantage when paired with the large leaves of hostas.
“Geraniums are a supporting cast, and you need that in the garden,” Parer says. Their flowers all have five equal-size petals that range in size from 1/2 to 2 1/2 inches wide. “I really like wildflowers and the quality that hardy geraniums bring to the garden,” Parer said. “The flowers are simple, by and large, but there are a few that are double. There’s something calming about single flowers.”
Most geranium flowers have veins in light, dark or contrasting hues. Plants may produce more flowering stems over the summer, but if the stems become untidy, you can cut them back a few inches. “You get the blast in spring, cut them back, forget about them and look at something else,” Parer says.