Annuals, Evergreen, Ground covers, Perennials, Flowers
The common name “geranium” is widely used for Pelargonium—but botanically speaking, it is not really accurate. To the botanist, pelargoniums are woody-based perennials (most of them are 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, are annuals and perennials native mainly to the Northern Hemisphere, bearing symmetrical flowers either singly or in clusters.
In the past, the commonly grown pelargoniums were P. x domesticum, Lady Washington pelargonium; P. x hortorum, common geranium (this group also includes variegated forms usually referred to as fancy-leafed or color-leafed geraniums); and P. peltatum, ivy geranium. Today, other kinds are increasingly available, including many with scented leaves.
Plants perform best in areas with warm, dry days and cool nights. They can be grown outdoors year-round where winters are very mild; in these areas, they bloom throughout warm weather. Elsewhere, they are summer annuals or houseplants. In cold-winter climates, move plants indoors before the first frost or take cuttings for next year.
Plant in any good, fast-draining soil. Amend poor alkaline 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 they are somewhat potbound. Common pests include aphids, whiteflies, and spider mites. Geranium (tobacco) budworm may be a problem in some areas; affected flowers look tattered or fail to open at all. Prevent or limit infestation by spraying plants with Bacillus thuringiensis (Bt).
Ivy geraniums are perennials in mild climates, and annuals anywhere. They grow to 1–1 1/2 ft. tall and trail (or hang) to 3–5 ft. wide. Rather succulent, glossy, bright green, 2–3-in.-wide leaves have pointed lobes and look something like those of ivy (Hedera). Inch-wide single or double flowers in rounded clusters of five to ten; colors include white, pink, rose, red, and lavender. Upper petals may be blotched or striped.
There are many named varieties. Use ivy geranium in hanging containers, window boxes, or raised beds; it also makes a good bank or groundcover (but not for erosion control). Because it does especially well with cool nights and bright days, ivy geranium is favored along the coast and in mountain gardens.
This hybrid perennial is grown everywhere as an annual. Erect or somewhat spreading, to 3 ft. tall and wide. Heart-shaped to kidney-shaped leaves are dark green, 2–4 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 but tends to get rangy. First-class potted plant. Some varieties are used in hanging baskets.
Succulent stemmed; reaches 1–2 ft. tall and wide as an annual. In mild climates where geraniums grow as perennials, older plants become woody and can top 3 ft. Round or kidney-shaped leaves are velvety, hairy, and aromatic, with edges indistinctly lobed and scalloped. Most varieties show a zone of deeper color that looks like a thick halo around the center of the leaf, though some have plain green foliage. Single or double flowers are flatter and smaller than those of P. x domesticum, but the clusters bear many more blossoms. Varieties are sold in white and shades of pink, rose, red, orange, lavender blue, and violet. Flowers may be solid colored, bicolored, speckled, or splashed with contrasting colors.
These plants are uniform, well branched, heat resistant, and available in many colors. Because they cost more than seed-grown geraniums, they’re more often purchased for containers than for bedding out.
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