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How to Grow: Hardy Geranium
full sun, part sun
Bloom Period and Seasonal Color
Late spring to early summer with some reblooming throughout the summer in colors such as white, blue and pink.
Mature Height x Spread
6 to 24 inches x 1 to 2 feet
Geraniums aren’t really geraniums. The geranium most gardeners refer to is actually Pelargonium, an annual flower. I cover those in the chapter on annuals. True geraniums are hardy perennials in New England that are low growing, free flowering in colors such as blue, white and pink. They are also called cranesbill geraniums because the seedpod resembles this bird’s bill. The flowers form above the lobed foliage and bloom off and on all summer. Keep the plant religiously deadheaded. This sprawling plant spreads a few feet wide, but pruning and dividing keeps it in bounds. The small, cupped-shaped flowers are attractive to bees and butterflies.
Where, When and How to Plant
Grow hardy geranium plants throughout New England. Plant locally purchased transplants or divisions from a friend’s garden in spring after all danger of frost has passed, until early fall. They grow and flower best in full sun on well-drained, compost-amended soil, but will still flower in part sun and on clay soils. Space plants 1 foot apart in beds.
Grow hardy geranium plants with plenty of water and fertilizer each spring with a layer of compost. Mulch around the base of plants to inhibit weed growth and keep the soil moist.
Regional Advice and Care
Hardy geraniums will repeat flower if deadheaded and cut back after the initial blooming period. Plants have a tidier look and flower better if divided every 3 to 4 years. To divide, in spring, dig up the clump and separate out 1-foot diameter divisions for replanting elsewhere or to give away. Hardy geraniums are one of the lowest maintenance perennials you can grow in your garden. However, in part shade or during wet summers they can get powdery mildew. Keep plants pruned and well spaced and clean up the dead leaves in fall to reduce the incidence of this disease.
Companion Planting and Design
Hardy geraniums are great filler plants in the perennial garden. Because they sprawl and flower in summer, they can fill in next to other plants that have finished blooming, such as peonies and iris; or compliment other summer blooming, such as roses, daylily and coreopsis. If you grow hardy geranium in the front of your flower border, keep them trimmed so they don’t look so messy. Plant more trailing varieties along a wall to cascade over the edge.
One of my favorite hardy geranium varieties is “Rozanne”. This variety has violet-blue flowers on a plant that grows to 2 feet tall. “Johnson’s Blue” is another similar sized blue blooming variety. “Ann Folkard” is a magenta colored flower variety that only grows 8 inches tall and is great in a rock garden or along a wall. “Album” has white flowers on 12-inch tall plants.
Excerpted from my book, New England Getting Started Garden Guide.