Pelargonium capitatum (Rose scented geranium)
Species: P. capitatum
Binomial name: Pelargonium capitatum
Common names: Rose scented geranium, Rose geranium, Rose pelargonium, Rose-scented pelargonium, Coastal geranium.
Pelargonium capitatum is a low, shrubby, softly hairy perennial that is native to South Africa. It grows to 100 cm in height and 1.5 m across. The stems are soft and coated in green, glandular hairs. Brushing against a bush releases a copious scent of the essential oil from damaged hairs. The scent varies from faint sweetness to a strong rosy scent. The popular names ‘Rose’ refer to the scent of the essential oils extracted from glandular tissue, not the flowers, which have hardly any scent to speak of.
The flowers range from white through various shades of pink to purple. Its preferred habitat is on sand dunes, but it is a fast grower on any reasonable base, including hard clay soil, so it readily colonises disturbed habitats.
Pelargonium capitatum is one of a number of related plants that have become a major problem in coastal regions of southwest Western Australia, where it invades banksia woodland and coastal heathland. It can be spread by seed and root fragments. Dispersal can be by wind, water or movement of soil soil.
The plants seed is elliptically shaped, with a feathered, tail-like coiled spiral structure attached. This tail allows the seed to drill and secure itself in soil if twisted by the wind or affected by movement of animals. Seed has high levels of physical dormancy, which can be broken by high and/or low winter temperatures.
Pelargonium capitatum is not a problem weed plant in New Zealand at present but it has the potential to become one. Wild plants have been reported in the coastal area of Eastbourne, Wellington.