Common name: Whitewood
Scientific name: Petrobium arboretum
IUCN status: Critical
Natural History
This plant is restricted to the remnant areas of the high altitude vegetation such as the Diana's Peak National Park and High Peak growing among tree ferns, cabbage trees and dogwoods. The widely scattered species, like the dogwood, is primarily threatened by the fragmentation and degradation of areas surviving original habitats compared to the amount or regeneration observed for the black cabbage there is very little regeneratin of whitewoods.
DESCRIPTION
This is the smallest of the cabbage trees which grows to a height of more than 4m. This tree is more upright, less speading than the black cabbage tree, with smaller leaves that are borne in opposite pairs. Each leaf is about 7.5cm long, boradly oval in shape with aa slightly serrated edge. The young leaves appear bronze in colour. The flower heads are borne at the ends of the branches in groups of six to eight. The flowers have a compositae structure, each are about 8mm across and composed of ten to twelwe greenish brown disc florets and whitish fay florets. Flowering occurs from March to June.
NUMBER OF SURVIVING POPULATIONS
The major populations of whitewoods can be found within the Diana's Peak National Park growing along side the dogwoods, black cabbages trees and tree fern thicket. They can also be found growing at Pleasant Valley, High Peak and the Depot. Whitewoods have been reintroduced to compartments ion the Peaks such as Newfoundland, Jockies, Warrens, Wells, Byron, Cuckolds and Washhouse tree ferns as part of the management programme. Specimen plants have been planted in the George Benjamin Arboretum.
CONSERVATION RECOVERY PROGRAMMES
Since 1995 whitewoods seeds and cuttings have been tken. The seeds are sown in the nursery and some have been placed in storage. The seedlings are used in replanting programmes on the Peaks. Seed viability is very low, thus very few seedlings can be produced. Seed that are sown immediately after they are collected have had the greatest success in germination. Seeds can survive freezer storage but it is suspected viability declines quickly in storage. I addition to collecting seed, cuttings have also been collected from as many individuals as possible, which root succesfully. These cuttings are used in developing a seed orchard at Taylors.
The idea of having a seed orchard is to have all the whitewoods growing together so that they are able to cross pollinate, producing seed that is outcrossed. This is in contrast to the present situation where populations and individuals have become small and isolated allowing inbreeding to happen. If we are succesful in obtaining seed from these trees which will be used for future replanting than hopefully this will lead to stronger populations.