The common indoor/outdoor plant that most people know as geranium is, botanically, Pelargonium. Considered here are true geraniums, which are hardy plants. Many types bloom over a fairly long period, bearing flowers that are attractive, though not as showy as those of Pelargonium. Carried singly or in clusters of two or three, flowers have five overlapping petals that look alike. (Pelargonium blossoms also have five petals, but two point in one direction, the other three in the opposite direction.) Colors include rose, blue, and purple; a few are pure pink or white. The beaklike fruit that follows the flowers accounts for the common name cranesbill. Leaves are roundish or kidney shaped, with lobed or deeply cut edges; plants may be upright or trailing. Good in perennial borders; some are useful as small-scale ground covers.
All of the species listed here appreciate afternoon shade and moist, well-drained soil. Clumps of most types can be left in place for many years before they decline due to crowding; at that point, divide clumps in early spring. Increase plantings by transplanting rooted portions from a clump's edge. Most types bloom heavily in spring and early summer, then go dormant when the weather gets hot in July and August. Resist browsing deer.
G. 'Ann Folkard'. Mounding, billowing plant (112 ft. high, to 5 ft. wide) with chartreuse leaves that age to light green. Saucer-shaped, 112-in.-wide blossoms are rich magenta purple suffused with pink and blue, centered and veined in black. Blooms from June through August. Effective planted at edge of patio and sprawling onto it.
G. 'Anne Thomson'. Similar to G. 'Ann Folkard' but more compact (1 ft. high, 3 ft. wide) and with greater heat tolerance.
G. 'Brookside'. Hybrid developed from G. pratense. To 212 ft. tall and wide, with deeply serrated leaves. Covered in late spring with rich blue, bowl-shaped flowers to 2 in. across. Somewhat similar to G. 'Johnson's Blue' but easier to grow.
G. xcantabrigiense. Excellent ground cover, 68 in. high, spreading slowly but widely. Dark green leaves 112212 in. wide, deeply cut with multiple lobes. 'Cambridge' has bright bluish pink flowers, 341 in. wide. The blooms of 'Biokovo' and 'St. Ola' are white blushed pale pink and slightly larger.
G. cinereum. From the Pyrenees. Grows to 6 in. tall, much wider, with deeply cut, soft gray-green leaves. Inch-wide pink flowers with darker veining appear in late spring and summer. 'Ballerina' has lilac-pink flowers with purple veining; blooms over a long summer season. 'Laurence Flatman' has slightly larger flowers of a deeper color. 'Purple Pillow' has bright purple flowers with dark purple veins. Variety G. c. subcaulescens (G. subcaulescens) has darker green leaves and deep purplish red flowers with black centers.
G. dalmaticum. From the Balkans. Low (45-in.) carpeting plant with glossy, 112-in., finely cut leaves and soft pink, inch-wide flowers in spring. Leaves turn orange and red in fall. Spreads slowly to make a 2-ft.-wide mat; useful in rock gardens.
G. endressii. From southern Europe to southwest Asia. Bushy plant to 1112 ft. tall, spreading to 2 ft. across. Leaves are 23 in. wide, deeply cut into five lobes. Rose-pink flowers to about 1 in. across.
G. himalayense (G. grandiflorum). Wiry, branching stems form a clump to 12 ft. high, spreading wider. Roundish, long-stalked, five-lobed leaves to 134 in. across. Clustered, 112- to 2-in.-wide flowers are lilac with purple veins and a red-purple eye. 'Graveteye' is a dependable selection; 'Baby Blue' has larger light blue flowers. 'Plenum' ('Birch Double') is less vigorous, with double flowers in light lavender.
G. 'Johnson's Blue'. Hybrid resembling its G. himalayense parent, but with more finely divided leaves and blue-violet, 2-in.-wide flowers.
G. macrorrhizum. From southern Europe. To 810 in. high, spreading by underground rootstocks and fleshy rhizomes that root on soil surface. Inch-wide magenta flowers in spring; fragrant, five- to seven-lobed, 4- to 8-in.-wide leaves that take on attractive tints in autumn. Good ground cover for small areas, though it can overwhelm delicate smaller plants. Selections include deep reddish purple 'Bevan's Variety'; pink 'Spessart'; 'Ingwersen's Variety', with soft bluish pink blossoms over a long season; and 'Album', bearing white flowers with pink sepals and stamens. Flowers of 'White-Ness' are pure white.
G. maculatum. WILD GERANIUM, WILD CRANESBILL. Native to eastern North America; the only commonly cultivated native cranesbill. To 1 ft. high, 2 ft. wide, deeply divided leaves and an abundance of lilac-pink, 1- to 112-in.-wide flowers in spring. 'Album' has white blooms. Leaves of 'Elizabeth Ann' and 'Espresso' are dark chocolate-brown.
G. x magnificum. Vigorous sterile hybrid that spreads steadily, forming broad clumps 22 ft. high and wide. Rounded, quilted, 3-in. leaves are divided into broad segments; take on red and orange tones in fall. Profuse 2-in. violet blossoms heavily veined in deep purple appear in late spring and summer. 'Rosemoor' is a choice selection with darkly veined, blue-violet flowers produced over an extended period.
G. x oxonianum. Among the best selections is 'Claridge Druce', which forms a vigorous clump 23 ft. tall, 3 ft. wide. Rounded, 3- to 4-in. leaves are deeply cut into broad, toothed lobes. Funnel-shaped, broad-petaled, 112- to 134-in., cool pink flowers with purplish veins bloom late spring to summer. Good large-scale ground cover but can overwhelm adjacent plants. Self-sows profusely; seedlings resemble parent, but blossoms often have narrower petals. 'Wargrave Pink' is similar in habit but a little less vigorous, with glossy, warm pink blossoms that resemble those of G. endressii.
G. phaeum. MOURNING WIDOW, DUSKY CRANESBILL. Shade-loving native of southern and central European mountains. Grows to 2 ft. high, 112 ft. wide. Leaves are basal, 34 in. across, shallowly cut into seven to nine tooth-edged lobes, often with brown markings. Bears clusters of dusky purple or maroon, 34- to 1-in. blossoms in May and June. 'Album' has blooms of pure white. 'Lily Lovell' has purplish maroon blooms with a white eye. Leaves of 'Margaret Wilson' are heavily streaked with creamy yellow; flowers are light purple. 'Samobor' has maroon flowers and leaves heavily marked with maroon.
G. platypetalum. From Turkey and the Caucasus. Clump 112 ft. high and wide with rounded, quilted, 4- to 8-in.-wide leaves, shallowly cut into seven to nine scalloped lobes. Saucer-shaped, 112- to 134-in. flowers with notched petals are deep violet blue with paler center and dark veins. Late spring bloomer.
G. pratense. MEADOW CRANESBILL. Native from Ireland to Siberia and Japan. Forms a clump 1122 ft. tall, 23 ft. wide. Hairy, 3- to 6-in. leaves on upright stalks are deeply cut into seven narrow, pointed, divided lobes. Flowers about 1 in. wide, typically blue with reddish veins. Self-sows profusely; cut to ground when flowers fade to prevent seedlings and encourage rebloom. 'Black Beauty' has dark purple leaves and light blue blooms. 'Midnight Reiter' has plum-colored foliage; the flowers are lavender-blue. 'Mrs. Kendall Clark' has pale blue flowers with lighter veins. 'Plenum Violaceum' ('Flore Pleno') has fully double, deep violet-blue blossoms. 'Striatum' has white blossoms irregularly splashed, streaked, or spotted with violet-blue.
G. 'Rozanne'. This naturally occurring hybrid between G. himalayense and G. wallichianum 'Buxton's Variety' is popular and easy to grow. Plants reach 1 2 ft. high and spread a little wider, forming a lush mound of deeply lobed, dark green leaves. Foliage takes on attractive red tones in the fall. Stunning flowers, to 2 in. wide, are rich violet-blue with darker veins and a large white eye. Blooms summer into fall.
G. sanguineum. BLOODY CRANESBILL. Native from western Europe to the Caucasus and Turkey. Grows 112 ft. high, with trailing stems spreading to 2 ft. Roundish, 1- to 212-in.-wide, dark green leaves with five to seven lobes; turn blood red in fall. Deep purple to almost crimson flowers, 112 in. wide, bloom from late spring well into summer. 'Album' is somewhat taller than the species and has white flowers. Other 1- to 112-ft. selections include 'John Elsley', pink with deeper pink veins; 'Max Frei', reddish purple; 'New Hampshire', deep purple; and 'Vision', reddish purple. 'Elke' (G. 'Elke') grows 10 in. tall and 3 ft. wide, with bright pink, red-veined flowers; petals are edged in white.
The variety G. s. striatum (G. s. 'Prostratum', G. lancastriense) is a dwarf formlower and more compact and an excellent choice for rock garden or foreground. It has light pink flowers heavily veined with red (its seedlings may vary somewhat).
G. sylvaticum. Native from Ireland to Siberia, south to Turkey. To 212 ft. tall and wide. Leaves are deeply lobed and toothed; inch-wide flowers range in color from bluish to reddish purple.
G. wallichianum. Native to the Himalayas. Grows to 1ft. tall and 3 ft. wide, with marbled, wrinkled, tooth-edged leaves. Lilac, 1- to 112-in. flowers with a white eye. 'Buxton's Variety' has pure blue flowers with a large white eye and striking black stamens.