At home on Rock of Gibraltar

Iberis gibraltarica has distinctive large flower heads. Photo by Gregor Richardson.
Iberis gibraltarica has distinctive large flower heads. Photo by Gregor Richardson.
The rocky limestone outcrops of Gibraltar resemble an enormous wild rock garden and are home to several unique species of plants.

One of these is the Gibraltar candytuft, Iberis gibraltarica, which grows abundantly in crevices on the north face of the Rock of Gibraltar.

This Iberis is a low-growing, evergreen shrub.

Its main flowering season starts in midwinter and continues into spring.

The flower heads are large, up to 8cm across.

The lower outer flowers have longer stems than the upper inner ones, giving the corymb a flat appearance.

Being in the cabbage family, Brassicaceae, each individual flower has four petals in the shape of a cross, or crucifix (the old name for the family was Cruciferae).

In the genus Iberis, the two inner petals are much larger than the outer, giving the flower the appearance of a tiny butterfly.

The individual blooms begin opening from the outside edge, darken with age and produce a flower head of various shades of pinkish-lavender.

This shrub enjoys a sunny, well-drained position and is hardy in Dunedin.

It can be short-lived, but is easily grown from seed.

Plants will benefit from a light prune after flowering, (if it ever stops), to keep the plant more compact.

Also native to the Atlas mountains of Morocco, members of the genus Iberis are mainly native to the region of Iberia.

The specimens flowering now in the rock garden at the Dunedin Botanic Garden have been grown from seed which was collected in the wild by the Alameda Gibraltar Botanic Gardens and sent as part of an international seed exchange programme.

The common name, candytuft, was originally given to Iberis umbellata, from Crete, and does not refer to candy, but has been derived from Candia, the old Venetian name for Heraklion, the capital of Crete.

- Robyn Freeth is the rock, water and alpine collection curator at the Dunedin Botanic Garden.