Empleurum unicapsulare

(L.f.) Skeels

Family : Rutaceae (citrus family)
Common names : false buchu, river buchu (Eng.); bergboegoe, wildeboegoe (Afr.)

Empleurum unicapsulareEmpleurum unicapsulare is a single-stemmed, evergreen shrub, which has a similar growth habit to a willow tree. It slender and upright growth form with its hanging, spreading branches and interesting flowers, makes it an ideal accent plant in any garden. . It belongs to the citrus family and its diagnostic characters are the undivided gland-dotted leaves, dehiscent fruit and flower structure.

Description
The false buchu is a shrub or small tree of about 4 m and is completely glabrous (hairless). The undivided, linear, dark green leaves, 20-60 x 3 mm, have finely serrated edges and are alternately arranged on the branches. They are richly endowed with oil glands which are visible on the underside of the leaves and when crushed have a resin-like scent.

The branches are erect, rod-like and brownish red. Branchlets are numerous, straight, slender and pale greenish yellow. A closer look shows that the branches are completely gland-dotted.

Empleurum unicapsulare is monoecious (bearing unisexual flowers on the same plant) or polygamous meaning having male, female and bisexual flowers on the same plant. The calyx of the flower is 4-lobed and petals are absent. It has four fertile stamens with the staminodes and disc absent. The ovary is superior with 2 ovules.

During the peak flowering season from April to September, small greenish flowers appear, either solitary or are borne in pairs in the leaf axils.

Flowers

Fruit is most plentiful after flowering between August and January. The fruit is a single-chambered or unicarpellate seed capsule, topped by a sword-shaped horn. It is glabrous (hairless), shiny, gland-dotted and about 17-20 mm long. This seed capsule only bears one black seed, which measures about 6.2-8.0 x 2.8-3.0 mm.

Distribution and Habitat
Growing in habitatThis genus has only two species, Empleurum unicapsulare and E. fragrans growing in the Western Cape. E. unicapsulare occurs on damp stream banks and seeps at high altitudes from the Cederberg to Port Elizabeth.

E. fragrans forms a wand-like shrub and is easily distinguished from E. unicapsulare by its smaller leaves (6-8 mm long). It grows naturally along streamside seeps of the Langeberg Mountains. Peak flowering is during October when one or two greenish flowers are borne in the axils of the leaves.

Derivation of name and historical aspects
Empleurum is derived from the Greek en, and pleuron/pleura, which is the membrane surrounding the lungs (the seed is contained within the membrous inner hull of the ripe capsule).

Ecology
The flowers attract pollinators such as bees and butterflies. The single seed is ejected from the ripe, hard capsule by the ballistic dispersal or catapult mechanism. The dispersed seed often germinates around the base of the plant.

Uses and cultural aspects
Empleurum unicapsulare has no known medicinal or cultural uses other than its use as a decorative plant.

Serrated leaves

Growing Empleurum unicapsulare

Empleurum unicapsulare is best planted as an accent plant to display its growth habit and hanging branches. When planting, make sure there is enough space around this buchu to encourage it to grow into a beautiful shrub or small tree. Plant in well-prepared soil, enriched with compost, balanced fertilizer and situated in a sunny spot in the garden.

Buchus naturally occur in a mixed fynbos and ideally should be used in this way in a garden. In your garden, create an interesting bed by planting it with companion plants such as restios, pelargoniums, Helichrysum, Erica, Protea and other buchu species such as Acmadenia mundiana, Adenandra obtusata, Agathosma lanceolata, A. ovata 'Kluitjieskraal ', A. mucronulta, Coleonema album, C. pulchellum and Diosma prama. It can be used as a potplant or as a filler plant, planted in masses, and creates an interesting hedge.

The start of the rainy season is the ideal time to start planting buchus in your garden (May to September). During this time, buchus establish themselves and will thus cope with warm, hot, summer weather and reduced rainfall. Buchus respond to fairly dense plantings, which help to retain soil moisture. An annual mulching of well-rotted compost is advised to reduce weeds and keep the soil temperature low.

Empleurum unicapsulare can be grown from seed or cuttings. Seed capsules are collected when the capsule is dark green and can be stored in a closed brown paper bag. The fresh buchu seed is sown in autumn. The seeds are sown in 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 damp. Germination occurs in one to two months.

Young seedlings are pricked out into 0.5 litre bags when four true leaves have developed, using a fynbos medium. Pinch out the growing tips of the seedlings to encourage bushy growth. Seedlings are planted in the garden the following autumn-winter season. Grown from seed, the plant produces flowers after two years.

Buchus grown from cuttings have the advantage of producing a larger flowering plant quicker than seedlings. Cutting material is selected from healthy plants. The ideal cutting is the tip, 50-70 mm in length, taken from the current year's growth. Prepare 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. Firmly place the cuttings in a medium of 50% bark and 50% polystyrene. Ideally, these cuttings should now be placed in an well-aerated propagation unit with a bottom heat of 24º C. Rooting occurs in 9-11 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 7-8 months. Tips of branches can be pinched back to encourage bushy growth. Feed regularly with a well-balanced nutrient. Yellow leaves can be treated with an application of iron chelate.  

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.
  • Bean, N. & Johns, A. 2005. Stellenbosch to Hermanus. South African Wild Flower Guide 5. Botanical Society of South Africa, Cape Town.

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Kirstenbosch National Botanical Garden
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