Pelargonium hortorum Seeds | Zonal Geranium
LATIN NAME: Pelargonium hortorum
COMMON NAME: Zonal Geranium
Plant Profile
The zonal geranium is not a species but a hybrid group, raised in Europe from two South African parents, Pelargonium zonale and Pelargonium inquinans. It is a soft shrubby plant of thirty to sixty centimetres with rounded scalloped leaves, often marked with a dark horseshoe zone, and heads of five-petalled flowers.
It is not a geranium at all. True Geranium, the cranesbills, are hardy perennials of the northern hemisphere, while Pelargonium comes from the winter-rainfall Cape and is tender. The mistake is in every garden centre, and it is worth knowing which plant is being sold. The stems are succulent and brittle, and a plant that is knocked over will root from the broken pieces if the ground is moist.
Science & Biotechnology
The dark zone on the leaf is anthocyanin laid down in the epidermis, and its intensity varies with light and with temperature. It has no function that is agreed on, though shading experiments suggest it may protect the leaf from excess radiation in the same way as red leaf undersides in other genera.
The plant is a hybrid and sets little seed, so named cultivars are raised from cuttings. F1 seed strains exist and are uniform, but they are rebuilt each year from parent lines. The genus is also unusual in having a nectar spur fused to the flower stalk, which is the character that separates Pelargonium from Geranium.
Uses & Benefits
It is a bedding and container plant, grown for months of colour on a windowsill or in a hanging basket, and it tolerates dry air better than most houseplants. In mild climates it becomes a small shrub that can be cut back hard each spring.
The leaves of scented pelargoniums, relatives rather than this plant, are used for oil and for flavouring, and the claim that any pelargonium repels mosquitoes is not supported: the plant releases its oil only when crushed, and a pot on a table does nothing. The rose-scented types are distilled for perfume in Réunion and in Egypt.
Growing from Seed
Sow F1 seed on the surface of a moist mix at twenty-one to twenty-four degrees and do not cover it, since light is needed. Germination takes a week to ten days, and the seedlings flower in ten to twelve weeks from sowing, which makes an early start worth the trouble.
Grow on in full sun and let the compost dry between waterings, since rot at the base is the commonest failure. Remove dead heads to keep the plant in flower, and watch for rust, which shows as brown rings on the leaf underside and spreads in still, humid air. Take cuttings in late summer for next year.
Our Take
A tender South African shrub sold under a European name, and the most reliable colour for a hot windowsill. Buy it as a cutting, not as a seed packet, unless you want the F1 strains.
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