Ivy geranium (Pelargonium peltatum, (L.) L'Hér. 1789)

Identity

Ivy geranium (Pelargonium peltatum (L.) L'Hér., 1789), also called ivy-leaved pelargonium or cascading geranium, is a trailing subshrub in the Geraniaceae family. It is one of the world's widely grown ornamental plants for balconies and patios. ^{1 4}

Despite the garden name, this plant is not a true Geranium. L'Héritier separated Pelargonium from that genus in 1789. Many true geraniums are hardy border perennials, whereas pelargoniums are frost-tender plants from southern Africa. ^{2 3}

Flexible stems make ivy geranium a familiar container plant, cascading over edges and flowering from spring until frost. Its habit suits window boxes and hanging baskets especially well. ^{2 6}

Recognition

Smooth, glossy, fleshy leaves and flexible trailing stems identify Pelargonium peltatum. Stems extend from 40 cm (16 in) to more than 1 m (3.3 ft). The leaves have five shallow lobes resembling ivy leaves, which explain the common name. ^{3 4}

The epithet refers to a precise feature: the leaf is slightly peltate, meaning its stalk attaches a little inside the blade's margin rather than at the notch. A darker semicircular band is sometimes visible on the blade. ^{1 3}

Loose umbels carry 2–10 flowers, white, pink, mauve or red according to cultivar. Each flower has bilateral symmetry and a nectar spur fused to its stalk. This less obvious feature separates pelargoniums from true geraniums with regularly symmetrical flowers. ^{4 2}

Useful taxonomy

Linnaeus first described the species as Geranium peltatum L. L'Héritier transferred it to Pelargonium in 1789; the accepted name is Pelargonium peltatum (L.) L'Hér. Several older scientific names occur in the literature:

• Geranium peltatum L., original name
• Pelargonium scutatum Sweet, historical synonym
• Pelargonium hederifolium Salisb., historical synonym
• Geraniospermum peltatum (L.) Kuntze, historical combination
• Dibrachya peltata (L.) Eckl. & Zeyh., historical combination

The accepted scientific name, Pelargonium peltatum, provides a stable reference. Trade names such as Ville de Paris, Decora and Cascade denote horticultural selections rather than separate species or botanical varieties. Most garden-center ivy geraniums are hybrids derived from this species. ^{1 7}

Habitat and range

In South Africa's Cape provinces, ivy geranium grows in thickets, on rocky slopes and along dry edges under Mediterranean to subtropical conditions. Within its native range, it flowers almost year-round, most strongly from August to October, during Southern Hemisphere spring. ^{1 3}

Mild, dry conditions suit this plant. It tolerates heat and brief drought but is damaged by frost, explaining its success on sunny balconies. Full sun and a freely draining growing medium are central to its cultivation. ^{2 6}

Cultivation has spread ivy geranium worldwide, with local naturalization in mild regions including the Mediterranean Basin, Australia and California. These introduced populations are distinct from its native South African range. ^{7 5}

Life cycle and reproduction

As a frost-tender perennial, Pelargonium peltatum remains green and flowers almost continuously in mild climates. In cold regions it is grown seasonally or sheltered from frost through winter. It is an evergreen, nondormant species rather than a herbaceous plant with winter dormancy. ^{3 2}

Nectar-bearing umbels are adapted to pollination by long-tongued insects and butterflies in its native range. After flowering, the dry fruit develops the elongated beak characteristic of Geraniaceae. Its resemblance to a stork's bill explains the genus name, from Greek pelargós, meaning stork. ^{4 1}

Gardeners usually propagate it from stem cuttings with a node in late summer. Take a stem 8–15 cm (3–6 in) long, let the cut dry for a few hours and root it in barely moist, freely draining mix. Roots develop in two to four weeks in warmth. Seed is possible, mainly for developing varieties, because hybrid seedlings do not reliably reproduce the parent. Easy propagation has helped balcony cultivars spread widely. ^{2 5}

Uses and risks

Cascades of summer flowers make Pelargonium peltatum chiefly an ornamental for tubs, window boxes and hanging baskets. Its long, generous flowering, heat tolerance and easy propagation make it a balcony and patio staple. ^{2 6}

Keep pets from eating the plant. ASPCA classifies Pelargonium garden geraniums as toxic to cats and dogs. Leaf oils, including geraniol and linalool, can cause digestive upset, depression and contact dermatitis. It is not considered dangerous to people, but containers should still be kept out of pets' reach. ^{8 5}

Varieties, look-alikes and related plants

Garden-center forms are cultivars and hybrids, rather than separate species. Ville de Paris is the classic pink balcony type; Decora and Cascade are vigorous trailing series. Tornado and Great Balls of Fire are modern, more compact, self-cleaning selections. Before buying, check for strong stems, an even habit and no rust beneath the leaves. ²

Common look-alikes include:

• Pelargonium x hortorum, zonal geranium, with upright growth and velvety leaves marked by a dark zone;
• true geraniums of the genus Geranium, hardy border perennials with regularly symmetrical flowers;
• Pelargonium grandiflorum, the source of florist geraniums.

Trailing stems, fleshy ivy-shaped leaves and the nectar spur fused to the flower stalk remain the most useful features for identifying Pelargonium peltatum sold as ivy geranium. ^{3 1}

Main sources

• Plants of the World Online / Kew, Pelargonium peltatum (L.) L'Hér.
• Royal Horticultural Society, Pelargonium peltatum - ivy-leaved geranium
• Missouri Botanical Garden, Pelargonium peltatum
• Encyclopaedia Britannica, geranium (genus Pelargonium)
• Plants For A Future, Pelargonium peltatum
• NC State Extension, Pelargonium peltatum
• USDA PLANTS Database, Pelargonium peltatum (L.) L'Hér.
• ASPCA, Geranium (Pelargonium) toxicity entry for cats and dogs