The bright mauve to purple flowers of Agathosma glabrata, commonly known as buchu, are an eye-catcher in any garden. Buchus are identified by the presence of small, round oil glands present on the leaves and fruit. Crushing the leaves of this buchu releases a sweet lemon scent. Buchus are easily identified in the veld when brushing against a bush and smelling the sweet to pungent aroma.
Agathosma glabrata is slow growing and reaches a height of 0.5 to 1 m; it is an attractive, single-stemmed shrub with a round and dense habit and is bright and colourful when in flower. Masses of mauve, purple, white or pink flowers are borne in terminal clusters consisting of about 12-20 individual flowers. The flowering season starts in late winter until midsummer (July to December).
Leaves are tiny, dark green, and are 3-7 mm long. They are alternatively arranged on the side branches. Older branches are dark brown compared with younger branches which are cream to light green-brown, and covered with tiny white hairs, which are also visible on the reverse side of the leaves. The small oil glands which are scattered on the underside of the leaf, emit the sweet lemon scent.
The seed capsule is two-chambered with one shiny black seed in each chamber. As the seed capsule ripens or matures, it turns from pale l to dark green. The seed is scattered by ballistic dispersal or a catapult mechanism. If the seed capsule feels hard and not soft, it can be harvested.
Distribution and Habitat
There are 150 species in the genus Agathosma and most of them are found in the Western Cape. Agathosma glabrata occurs naturally in damp sandy plains and dune slacks from Darling to the Cape Peninsula.
Derivation of name and horticultural aspects
Agathosma is derived from the Greek agathos meaning pleasant, and osme meaning smell. This refers to the volatile oil in the glands on the leaves and fruit, and the word buchu is commonly used to describe indigenous small-leafed shrubs which release a pleasant to pungent aroma when touched. Each buchu species has its own unique scent. The Khoikhoi used the word buchu for an aromatic herb.
During the flowering season, masses of colourful flowers attract bees, butterflies and other insects which pollinate the flowers. Seed collected from fully ripened capsules show a higher germination percentage. If seed capsules are picked too early, the embryos are not developed and the seed will not be viable.
Uses and cultural aspects
Agathosma glabrata is an ideal garden plant for its aromatic leaves and beautiful flowers. Planted in masses or in-groups of 3, 5 or 9 in small garden beds, it makes a colourful display. It can be used as a border or filler plant in a mixed fynbos bed with small to medium-sized plants. It can also be used as a pot- or container plant that will brighten up any patio.
A. betulina and A. crenulata are grown commercially for their oil content. The oil is extracted from the leaves and is used in the production of cosmetics, soaps and food colourants. The essential oils are used medicinally for their antiseptic and diuretic properties. It is used in the treatment of renal disorders and chest complaints.
Growing Agathosma glabrata
Buchus can be successfully grown from seed or cuttings. Fresh buchu seed is sown in autumn (March to April). The seed are is sown into a tray containing a well-drained medium of equal portions of sand, loam and compost. Use some of the medium to cover the seed and water. Place in a covered area with good light and air circulation. Keep medium to damp. Germination occurs in one to two months.
Young seedlings are pricked out into 0.5 l bags when four true leaves have developed, using a fynbos medium. Feed plants regularly but sparingly with a well-balanced ferilizer. Pinch out the growing tips of the seedlings to encourage bushy growth. Flowers are produced after two years.
After flowering, plants develop new shoots or branches, which are is ideal for tip, stem or heel cuttings. Collect plant material early in the morning to reduce stress. Cuttings have the advantage of producing a larger flowering plant quicker than seedlings. Tip cuttings, 50-70 mm, are taken from the current year's growth. Prepare cuttings by making a clean cut below the node and remove the a third of the foliage. Dip the base of the cutting in a rooting hormone such as Seradix 2. Firmly place the cuttings in a medium of 50% bark and 50% polystyrene and water cuttings with a fungicide. Ideally these cuttings should now be placed in an well-aerated propagation unit with a bottom heat of 24ºC. Rooting occurs in 9 to 11 weeks. Carefully pot the rooted cuttings using a well-drained, humus-rich fynbos potting medium (2 parts leaf mould, 1 part coarse sand). Plants will be ready for planting in seven to eight months, ideally during autumn to spring. season. Feed regularly with a well-balanced nutrient. Yellow leaves can be treated with an application of iron chelate.
Agathosma glabrata as well as most of the species found in the Rutaceae family are best grown in the garden in full sun, in soil that is alkaline to acidic, well-drained and composted. Before planting, water the area and prepare the bed by digging over the soil, adding compost and a slow release fertilizer. Plant out in groups of 3 to 5, 20-30 cm apart, with enough space to grow. It is a slow-growing plant and should not be planted too close to faster growing plants. A layer of mulch is added after planting and annually to keep soil and roots cool in summer, retain soil moisture and reduce weeds. Buchus are best planted out during autumn, winter and spring. Plants require good watering in winter and moderate watering in summer. Do not allow plants to dry out, and avoid cultivating the soil around the roots of these fynbos plants. They are water-wise plants and once established in your garden they will survive long periods of drought and will withstand a fair amount of frost.
Agathosma glabrata is used as an accent plant, in a rockery, or in a mixed fynbos bed with companion plants such as Erica versicolor, Protea repens (sugarbush), Leucospermum cordifolium (pincushion), Chondropetalum tectorum, Pelargonium cucullatum (tree pelargonium, P. betulinum (camphor-scented pelargonium) and herbaceous perennials such as Lobelia valida, Geranium incanum, and Scabiosa incisa. Interesting buchu species are Acmadenia heterophylla, Agathosma lanceolata (honey buchu), Adenandra uniflora (china flower), and Coleonema album (white confetti bush).
References and further reading
- Gold, M. 1992. The buchus: cultivation and propagation. National Botanical Institute, Kirstenbosch.
- Goldblatt, P. & Manning, J. 2000. Cape plants. A conspectus of the Cape flora of South Africa. Strelitzia 9. National Botanical Institute, Pretoria & Missouri Botanical Garden, Missouri.
- Brown, N. & Duncan, G. 2006. Grow fynbos plants. Kirstenbosch Gardening Series. South African National Biodiversity Institute, Cape Town.