HARDINESS: Zones 3 to 8
PREFERRED SOIL pH: Neutral to slightly acid
PREFERRED SOIL TYPE: Average
PREFERRED LIGHT: Sun to partial shade
ATTRIBUTES: Flowers in many colors on spreading plants; for beds, groundcover
SEASON OF INTEREST: Spring through fall
FAVORITES: 'Johnson's Blue', 'War-grave Pink' in sun; 'Be-van's variety in shade
QUIRKS: Winter hardiness varies greatly with species
GOOD NEIGHBORS: Campanula, dayfily, dianmus, hydrangea, iris, lily, lobelia, peony
WHERE IT GROWS BEST: Sun to partial shade in cool-summer climates
POTENTIAL PROBLEMS: Excessive summer heat and drought may temporarily shorten flowering
RENEWING PLANTS: Lives many years; divide crowded clumps every 3-4 years
CRITTER RESISTANCE: Good except for slugs in damp areas
SOURCE: Bedding plants, division
DIMENSIONS: 6-24 in (15.2-61 cm) tall and equally wide
Geranium in the Landscape
Although the name geranium is usually used to describe the bright-flowered summer bedding annuals, perennial geraniums are the true geraniums from a botanical point of view. Also commonly called cranesbill or hardy geraniums, these plants produce masses of flowers with fluttery, thin petals in luminous color shades of rose, white, blue, lavender, purple, and carmine, and some flowers are punctuated with darker centers and veins. Each charming flower is about 1 in (2.5 cm) in diameter, and the blooms are held loosely on stems that range from a few inches to 2 ft (0.6 m) long, depending on the species. The ferny, divided foliage is deep green through spring and summer, often with chocolate markings, and changes to shades of fiery red and orange in fall.
Geraniums play plenty of garden roles beyond being accents in the perennial border, where they provide soft color for many weeks Some geraniums can be used as groundcovers, and others are sufficiently wild to hold their own in a woodland setting.
Geraniums for Every Purpose
Geraniums are a large and diverse group, with plants adapted to practically any garden purpose or spot. Because they vary so drastically in their preferences for light and root space, the best way to select a geranium is to match its needs to your situation. Here are some matchups that are bound to work.
In Flower Borders
Hardy and reliable from Zones 3 to 8, Geranium x oxonionum 'Claridge Druce' is an easily grown, spreading, pink-flowering plant, that is 18 in (45.7 cm) tall and can grow twice as wide. It blooms prolifically all summer and has handsome gray-green leaves. A closely related hybrid, 'Johnson's Blue', adds another shade to the geranium rainbow with purple-veined sky blue blossoms in early summer on plants that are 15-18 in (38-45.7 cm) tall and equally wide. Another rich addition to the perennial border with an almost vining habit is 'Ann Folkard', which grows 20 in (50.8 cm) tall and 24 in (61 cm) wide, bearing rich purple flowers for 4 months or more. Although 'Ann Folkard' is a great mixer in a flower border, its spreading habit makes it suitable as a groundcover. too. Let it weave through other plants for a charming effect.
Geraniums for Groundcovers
Cultivars of G. macrorrhizum, sometimes called bigroot geranium, are equipped with thick roots that help them spread into a tight mat of foliage 12 in (30.5 cm) tall and 24 in (61 cm) wide. Like other bigroot geraniums, magenta-flowered 'Bevan's Variety' tolerates dry shade, so it works as groundcover beneath trees. Where shade is limited to only part of the day, G. endressii 'Wargrave Pink' also spreads into a mass 24 in (61 cm) or more in width with the help of shallow, wandering rhizomes. It flowers grandly, bristling with porcelain pink blossoms in late spring and early summer.
The species known as bloody cranesbill, G. sanguineum, includes numerous cultivars that are hardy enough to withstand both Zone 3 winters and the humid summers of Geraniums with thick, ground-hugging growth are ideal for use as groundcovers.
Zones 7 and 8. Varieties vary in color and compactness, but all can be used as groundcover when grown in close quarters. Most cultivars have deep mauve-pink flowers, but if you want a lighter hue, consider long-blooming 'Striatum', which has light pink petals streaked with reddish veins.
In Woodland Gardens
Wood geranium, or G. maculatum, is native to North America's eastern forests and makes a lovely companion to ferns, with its pale rose to lavender flowers brightening the shade. Not only shade-loving but drought-tolerant as well, G. maculatum blooms in late spring on 12—18 in (30.5-45.7 cm) plants of the same width. Its flowering time is limited to spring, however, and the plants often become dormant by midsummer.
In Rock Gardens
In high-rainfall areas of Zones 5 to 7, grow geraniums that require excellent drainage in the fast-draining environs of a rock garden. Though these plants can't tolerate having wet roots, they handle abundant sun without complaint. Crevice-loving G. x cantabrigiense 'Biokovo' grows up to 12 in (30.5 cm) wide and tall, gleaming with masses of white flowers tinged delicately with pink. For a more colorful pink flower with contrasting dark centers, G. cinereum 'Ballerina' makes a charming rock garden plant.
In spring, set bare-root or container-grown plants 12 in (30.5 cm) or more apart in good garden soil, amended if necessary with compost or peat moss to improve its drainage and texture. Make groups of at least 3 or more plants and water well after planting. If taller types become leggy in midsummer, cut them back by half their size, promoting a new crop of leaves and a second set of flowers for late summer and early fall.
Geraniums are virtually disease and insect free except for slugs, which occasionally chew holes in the leaves,
especially in shady sites. Handpick and dispose of them at twilight, or set out saucers of beer to lure and drown them. Leaves of hardy geraniums can become mottled with random red spots in summer, but this is a natural coloring and does not hurt the plants.
Increasing the Bounty
Geranium clumps are easily divided when they become crowded. Pick an overcast day in spring or fall to do the job. If you're dividing in fall, cut the foliage back by about one-third to make it easier to see where to cut the roots apart. Dig up the clump and separate the somewhat stiff main roots. Reset the divisions into the garden, spacing them at least 12 in (30.5 cm) apart and taking care not to bury the growing points, or crowns.