The common indoor/outdoor plant most people know as geranium is, botanically, Pelargonium. Considered here are true geraniums, which are mostly hardy plants. Many types bloom over a long period, bearing flowers that are attractive though not always as showy as those of pelargoniums. Carried singly or in few-flowered clusters, blossoms have five overlapping petals that look alike. (Pelargonium flowers also have five petals, but two point in one direction, while the other three point in the opposite direction.) Colors include blue, purple, magenta, and bluish rose; some are pure pink or white. Beak-like fruit that follows the flowers accounts for the common name “cranesbill.” Leaves are roundish or kidney shaped, lobed or deeply cut; plants may be upright or trailing.
Good in rock gardens, perennial borders; some are useful as small- or large-scale ground covers. A few shrubby species are good for holding slopes. Best climates for most geraniums are cool- and mild-summer regions, where plants can grow in full sun or light shade. In hot-summer areas, give afternoon shade. South African species are less cold hardy but more tolerant of heat, afternoon sun. All species appreciate moist,well-drained soil.
Some geraniums benefit from being cut back after flowering or in the fall; these are noted in text. Clumps of most types can be left in place for many years before they decline due to crowding; at that point, divide in early spring. Increase by transplanting rooted portions from a clump’s edge; or take cuttings. Many produce lots of seedlings, and some can become naturalized pests.
Native from Ireland to Siberia and Japan. Forms a clump 1 1/2–2 ft. tall, 2– 3 ft. wide. Hairy, 3–6-in. leaves on upright stalks are deeply cut into seven narrow, pointed, divided lobes. Flowers are about 1 in. wide, typically blue with reddish veins; bloom from spring through summer. Self-seeds profusely; cut to ground when flowers fade to prevent seedlings and encourage rebloom.
Native to southern Europe, Caucasus. Compact, leafy, aggressive, spreading by volunteer seedlings; onc...
Native from central Europe to Siberia. To 1 1/2 ft. high, 1 ft.wide. Pale blue or white flowers i...
To 8–15 ft. tall and wide; horizontal branching pattern gives plant a tiered look. Strongly vein...