The common name geranium is widely used for members of the genus Pelargoniumbut botanically speaking, it is not really accurate. Pelargoniums are woody-based perennials (most of them native to South Africa) that endure light frosts but not hard freezes and have slightly asymmetrical flowers in clusters. True geraniums, on the other hand, belong to the genus Geraniumannuals and peren- nials (some woody based) native mainly to the Northern Hemisphere, bearing symmetrical flowers either singly or in clusters.
P. cordifolium. HEARTLEAF GERANIUM. Rounded plant to 4 ft. tall and wide, with 212-in., dull green, toothed and lobed leaves. Loose clusters of reddish purple, 1-in. flowers. Good for borders.
P. x domesticum. LADY WASHINGTON GERANIUM, MARTHA WASHINGTON GERANIUM. Erect or somewhat spreading, to 3 ft. tall and wide. Rangier than P. x hortorum. Heart-shaped to kidney-shaped leaves are dark green, 24 in. wide, with crinkled margins and unequal sharp teeth. Loose, rounded clusters of large (2-in. or wider), showy flowers; colors include white and many shades of pink, red, lavender, purple, with brilliant blotches and markings of darker colors. Can be planted in beds if pruned hard after flowering to prevent lanky, rangy growth. First-class potted plant. Some selections are used in hanging baskets. Most suffer during extended high temperatures, but the hybrid Grandirosa series is surprisingly heat tolerant.
P. x hortorum. COMMON GERANIUM, GARDEN GERANIUM. Succulent stemmed; grows to 3 ft. or more high and wide. In mild climates, older plants grown in the open become woody. Round or kidney-shaped leaves are velvety and hairy, soft to the touch, aromatic, edges indistinctly lobed and scallop toothed; most selections show a zone of deeper color just inside edge of leaf, though some have plain green foliage. Flowers are single or double; they are flatter and smaller than those of P. domesticum, but clusters bear many more blossoms. Many selections are sold, in white and shades of pink, rose, red, orange, and violet; flowers are usually solid colored.
Tough, attractive geraniums for outdoor bedding can be grown from seed; will flower the first summer. Available strains include Americana (bright green foliage, compact); Eclipse (dark green foliage, compact); Elite (quick to reach blooming stage, compact, needs no pinching); Maverick (open habit with many flowering stems); Multibloom (compact, early blooming); and Orbit (distinct leaf zoning; broad, rounded flower clusters). 'Orange Appeal', a seed-grown selection, has blooms in pure bright orange. There are also dwarf, cactus-flowered, and other novelty types.
Fancy-leafed or color-leafed selections have zones, borders, or splashes of brown, gold, red, white, and green in various combinations. Some also have highly attractive flowers. 'Golden Ears', 1 ft. high and wide, has small, deeply cut, almost star-shaped leaves of deep bronzy red with a wide border of chartreuse; flowers are bright coral. 'Vancouver Centennial' is very similar if not identical. 'Mrs. Pollock' has green leaves with a red zone and a creamy yellow margin; it bears vermilion blooms.
Common geraniums sometimes stop blooming during extended periods of high summer heata condition known as heat check. (They'll resume blooming when cooler weather arrives.) To avoid this condition, give plants light afternoon shade; or grow heat-tolerant types, such as the Americana, Eclipse, Maverick, or Orbit series.
P. hybrids. Crossing zonal geraniums and ivy geraniums has produced garden hardy selections. Double Take series has semidouble flowers that are slow to shatter. Calliope and Caliente series are a geranium lover's answer to Southern summer heat. Place them where they get all-day sun in the Upper and Middle South, but afternoon shade in the Lower and Coastal South.
P. peltatum. IVY GERANIUM. To 112 ft. tall, trailing to 3 ft. wide. Rather succulent, 2- to 3-in.-wide, glossy, bright green leaves with pointed lobes resemble foliage of ivy (Hedera). Spectacular summer show of single or double, inch-wide flowers in rounded clusters of five to ten; colors include white, pink, rose, red, salmon, and lavender. Upper petals may be blotched or striped. Many named selections are available. Most types cannot tolerate extended heat and are grown as summer annuals only in the Upper and Middle South (though they perform well as winter annuals in the Coastal and Tropical South). However, heat-tolerant Blizzard and Cascade and Summer Showers series perform well throughout summer in much of the Lower South, as well as farther north. Focus series is compact with dark leaves for dense baskets. Use ivy geraniums in hanging baskets, window boxes, and tall planters.
Scented geraniums. Many aromatic species, hybrids, and selections are available. Most grow 13 ft. tall, spreading as wide as high. Foliage scent is the main draw; clusters of small, typically white or rosy flowers are secondary in appeal. Leaves vary in shape from nearly round to finely cut and almost ferny; they range in size from minute to 4 in. across. Plants' common names usually refer to the fragrance of their leaves: almond geranium (P. quercifolium), apple geranium (P. odoratissimum), lime geranium (P. nervosum), nutmeg geranium (P. fragrans 'Nutmeg'), peppermint geranium (P. tomentosum). There are several rose geraniums, including P. capitatum, P. graveolens, and P. 'Lady Plymouth'. Various types offer lemon fragrance, including P. crispum and P. c. 'Prince Rupert'. All scented geraniums are good for herb gardens, edgings, front of borders, window boxes, hanging baskets; peppermint geranium makes a good ground cover in frost-free gardens. Use fresh leaves of all types for flavoring jelly and iced drinks; use dried leaves in sachets and potpourri.
Plant in any good, fast-draining soil. Amend poor soil with plenty of organic matter. Geraniums growing in good garden soil need little fertilizer; those in light, sandy soil should receive two or three feedings during active growth. Remove faded flowers regularly to encourage new bloom. Pinch growing tips of young, small plants to force side branches. All geraniums do well in pots; they bloom best when somewhat pot-bound. Common pests include aphids, whiteflies, and spider mites. Tobacco budworm may be a problem in some areas; affected flowers look tattered or fail to open at all. Most pests easily controlled by spraying with neem oil or spinosad.