Agathosma mucronulata is an attractive evergreen aromatic shrub, belonging to the Rutaceae family. This family also includes the Cape chestnut, Calodendrum capense and the citrus fruits. The common characteristic is the presence of oil glands, visible as tiny dots, on the leaves and fruits.

Agathosma mucronulata forms a neat, compact, rounded upright shrub 0.8-1 m tall. The leaves, which have a pungent almost turpentine-like scent, are spirally arranged around the stem and the apex of the leaf terminates in a sharp point. Masses of white flowers are produced during winter to spring (July to October). The flowers are small, with five petals arranged in a star, and are borne in lax terminal clusters. Each white petal is marked with 5 or 6 brown dots, which adds to the attractiveness of the flower. During the flowering period, the bush comes alive with bees and butterflies, which visit and pollinate the flowers. The three-chambered seed capsules are formed after pollination. These ripen during early summer (October-November) and when ready, burst open to release the seed with surprising force. This phenomenon is known as ballistic dispersal. Buchu seed is best collected when the seed capsule is very hard, just before it splits open. This is difficult to judge, and covering the branch ends with netting to capture the seed as it is catapulted out of the seed capsule is also effective.

Agathosma mucronulata occurs in mountain fynbos on the drier middle slopes around the Western Cape town of Uniondale, in the south-eastern part of the winter rainfall region of South Africa in Western Cape.

There are about 140 species in the genus Agathosma and most of them are found in the Western Cape. The genus name Agathosma is derived from the Greek agathos meaning pleasant or good and osme, scent or smell, referring to the pleasant scent emitted by the leaves and fruits which is caused by the presence of volatile oils in the leaves and fruit. The species name mucronulata is derived from the Latin for sharply pointed and refers to the shape of the leaf with its pointed apex.

Agathosma mucronulata is not a medicinal plant. The true buchus are A. betulina and A. crenulata. These two species are now grown commercially and the oil is extracted for use in cosmetics, soaps, food colourant, and medicinally for the treatment of stomach complaints, kidney and urinary tract disorders, and for colds, flu, coughs and other chest complaints.

Growing Agathosma mucronulata

Agathosma mucronulata does best when planted in full sun and needs adequate water during the hot summer months. It requires a soil that is well drained, and enriched with well-rotted compost (leaf mould) and a well-balanced slow-release fertilizer (3:2:1). It is slow growing and needs space in the garden bed to allow it to develop to its full potential, without being squashed by other faster growing plants.

Planting buchus into the garden is best done after the first good winter rains have fallen (May to July). Buchus respond well to fairly dense plantings, so plant a number of the same species fairly close together e.g. in groups of three of five, and in this way you will get a more dense and floriferous bush and help to retain soil moisture. A good thick mulching of well-rotted compost applied once a year will reduce weed growth, keep the soil temperature even, and conserve moisture during the hot dry summer.

Buchus occur naturally in mixed fynbos and are ideally suited to the fynbos garden, grown with other fynbos plants such as proteas, ericas, restios, pelargoniums, vygies, helichrysums, phylicas and felicias. Agathosma mucronulata also makes an attractive border plant, it is a useful filler plant, and it can be used in the rockery. To enjoy the scented foliage, plant it beside a path or in a container on a patio, where it will release its fragrance whenever it is touched. Other species suitable for the garden include Agathosma lanceolata and Agathosma ovata 'Kluitjieskraal'.

Buchus can be grown from seed or cuttings. Fresh buchu seed should be sown in autumn (April). The seed 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 free air circulation and keep damp. Germination occurs in 1 to 2 months. When the first four true leaves have developed, the young seedlings are pricked out into 0.5 litre bags containing a well-drained, humus-enriched potting medium (e.g. 2 parts leaf mould : 1 part coarse sand). Feed regularly but sparingly with a well-balanced fertilizer. Pinch out the growing tips of the seedlings to encourage bushy growth. Flowers are produced after two years.

Cuttings have the advantage of producing a larger plant that will reach flowering size sooner than seedlings. Tip cuttings, 50-70 mm, are taken from the current season's growth in spring (September to November). Prepare the cuttings by making a clean cut below the node and remove a third of the foliage. Dip the base of the cutting in a rooting hormone such as Seradix 2. Plant the cuttings firmly in a medium of 50% bark and 50% polystyrene. Ideally these cuttings should now be placed in a well-aerated propagation unit with bottom heat of 24° C and intermittent mist. Rooting occurs in 9 to 11 weeks and a weaning period of 2 weeks is recommended. Carefully pot the rooted cuttings into a well-drained, humus-enriched potting medium (e.g. 2 parts leaf mould : 1 part coarse sand). Feed regularly but sparingly with a well-balanced fertilizer. Yellow leaves can be treated with an application of iron chelate. Plants will be ready for planting in 7 to 8 months.

References

• 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.
• LEISTNER, O.A. (ed.). 2000. Seed plants of southern Africa: families and genera, Strelitzia 10. National Botanical Institute, Pretoria.
• JACKSON, W.P.U. 1990. Origins and meanings of names of South African plant genera. University of Cape Town.

Norma Jodamus & Alice Notten
Kirstenbosch National Botanical Garden
July 2002