Otholobium bracteolatum
Introduction
A resilient, beautiful, sprawling shrub, not easily missed because of its pretty mauve and white flowers, which are borne in dense rounded inflorescences in summer. This low-growing shrub is ideal for sandy coastal gardens and for rehabilitation of disturbed coastal sand in Fynbos.
Description
Description
Otholobium bracteolatum is a sprawling shrub, up to 2 m tall. The leaves are sub sessile, 3-foliolate with symmetrical leaflets which are glandular and wedge-shaped. When young, the leaves are covered with pressed hairs.
The inflorescence is a dense cluster of blue, white and violet flowers, which make it easier to spot the plant from a distance. The flowers are 8–10 mm long, with a glandular, soft-haired calyx. The flowering time for this species is in summer, between November and April.
Otholobium bracteolatum bears 4 mm long, 2 mm wide fruits, which are papery, reticulate and finely hairy when young and at maturity it is enclosed by the persistent calyx. The seeds are ellipsoid, 2–3 mm long, 1.5–2.0 mm wide, dark chestnut or black.
Conservation Status
Status
According to the Red List of South African plants, Otholobium bracteolatum is not threatened, and is assessed as Least Concern (LC).
The Millennium Seed Bank Partnership (MSBP) deals with seed conservation for research purposes, germination tests and for future restoration. Seeds of Otholobium bracteolatum were collected in a nature reserve on the Cape Flats by the MSBP team in the Western Cape, South Africa. This is a new collection at the MSBP, which means that Otholobium bracteolatum seeds have never been collected and banked at the MSBP before. The seeds will be shipped to the MSBP in Kew, where they will be banked and kept in freezers for long-term storage.
Distribution and habitat
Distribution description
Otholobium bracteolatum is found in moist places and occurs from Saldanha and Cape Town in the Western Cape, to Grahamstown in the Eastern Cape, growing both on the plains and mountains below 170 m altitude, in coastal sandveld and on limestone hills.
Otholobium bracteolatum is easily confused with O. fruticans (Cape Town pea), but they differ in flower colour, growth habit and habitat. O. fruticans is a trailing, semi-shrub that grows up to 400 mm high, with a spread of 500 mm to 1 m and only occurs on the Cape Peninsula, in mountain fynbos, on steep, rocky slopes, at 180–600 m altitude.
Derivation of name and historical aspects
History
The genus name Otholobium , pronounced ‘oh-tho-LOH-bee-um’, is derived from the Greek otheo, meaning to ‘burst forth’ and lobion, which means ‘small pod’, because the fruit appears to be pushing out of the calyx. The species name bracteolatum means ‘with bracts’.
Otholobium bracteolatum was previously known as Psoralea algoensis, then Psoralea bracteolata, which included the varieties P. bracteata var. vera, P. bracteata var. bracteolata and P. bracteata var. algoensis. None of the varieties were found to be true to their characters, even when traced through many specimens. More specimens were counted showing intermediate forms. After a comparison of the accumulated materials of several herbaria, these varieties were declared synonymous with Psoralea bracteata, which is now a synonym for Otholobium bracteolatum.
Otholobium is a genus of flowering plants in the Fabaceae, with 53 species. This genus was created by Charles Stirton in the 1980s to house the 3-foliolate, recurved, mucronate-leaved, glandular psoraleas and the psoraleas that do not have the 2- or 3-lobed cupulate structure on the flower pedicel.
Ecology
Ecology
Otholobium bracteolatum is a resprouter and resprouters are plant species that can survive fire by the activation of dormant vegetative buds to produce regrowth. This species is bee pollinated; the Cape honey bees search for nectar and pollen inside the flowers, enabling the plants to reproduce. This species has hard dry seeds which are dispersed by wind or water, as most of the species occur along the riverine areas and wet mountains.
Uses
Use
As one of the plants growing on the fore-dunes, Otholobium brateolatum has developed all sorts of defence mechanisms to survive harsh coastal conditions. The hair covering the leaves protects the plant against transpiration and desiccation. The extensive branches and the deep root system enable the plant to stand and survive the strong winds from the sea. These are some of the characteristics which make this plant ideal for rehabilitation on degraded coastal dunes. Otholobium bracteolatum is drought tolerant and used mostly for xeriscaping.
Otholobium bracteolatum has great horticultural potential in the landscape industry, because of its pretty mauve and white flowers, which are borne in compact rounded heads. The plant can be used in water-wise gardening because of its adaptations to survive on little water.
Growing Otholobium bracteolatum
Grow
Otholobium bracteolatum can be propagated by both cuttings and seeds. Propagation by stem cuttings can take place in summer. Mix half perlite and half well-composted fine-milled bark (if not fine sift it). Take cuttings from vigorously growing mother plants; take semi-hard wood material that is neither too hard, nor too soft. Place the cutting tray under intermittent mist on a heated bench and monitor cuttings till rooting has taken place.
Sow seeds in spring in well-composted bark, mixed with 15% sand. Treat seeds with fungicide to prevent damping off. Place your seeds on the surface of your sowing tray and thinly cover it with the same medium. Place your tray in a well-lit, warm environment and water when necessary. To sow in sandy soil, in situ, some protection for seed and seedling is required by building wind barriers to slow down the movement of sand. Early autumn is generally the ideal time to plant young plants or sow seeds in the Western Cape.
References
- Foden, W. & Potter, L. 2005. Otholobium bracteolatum (Eckl. & Zeyh.) C.H.Stirt. National Assessment: Red List of South African plants version 2017.1. Accessed on 2019/04/10.
- Harvey, W.H. 1811–1866. Flora capensis: being a systematic description of the plants of the Cape Colony, Caffraria, & Port Natal (and neighbouring territories) Volume 2.
- Manning, J. & Goldblatt, P. 2012. Plants of the Greater Cape Floristic Region 1: the Core Cape Flora. Strelitzia 29. South African National Biodiversity Institute, Pretoria.
- Manning, J. 2007. Field guide to Fynbos. Struik Publishers, Cape Town.
- Simon C., Power, S.C., Cramer, M.D.,G. Anthony Verboom, G.A. & Chimphango, S.B.M. 2011. Legume seeders of the Cape Floristic Region inhabit more fertile soils than congeneric resprouters — sometimes. Plant Ecology, 212(12): 1979–1989.
- Stirton, C. 1989. A revision of Otholobium C.H. Stirton (Papilionoideae, Leguminosae). M.Sc. thesis, University of Cape Town, Cape Town.
- The Fynbos Hub. Rehabilitation of coastal sands in the fynbos region. Posted 2012. Retrieved 10 Apr 2019. http://www.fynboshub.co.za/fynbos-gardening/rehabilitation-of-coastal-sands-in-the-fynbos-region/
- Velembo-Mhlauli, S.A. 2017–08. Otholobium fruticans (L.) C.H.Stirt. (Fabaceae). PlantZAfrica. Internet 5 pp. http://pza.sanbi.org/otholobium-fruticans
Credits
Naomi Mdayi
Millennium Seed Bank Partnership (MSBP)
May 2019
Plant Attributes:
Plant Type: Shrub
SA Distribution: Eastern Cape, Western Cape
Soil type: Sandy, Loam
Flowering season: Spring, Early Summer, Late Summer, Autumn
PH: Acid, Alkaline, Neutral
Flower colour: White, Mauve/Lilac
Aspect: Full Sun
Gardening skill: Average
Special Features:
Drought resistant
Fragrant
Feeds honeybees
Horticultural zones
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