Diosma prama I.Williams
Common names: Little Karoo bitter-buchu
Take a closer look at Diosma prama with masses of tiny creamy white flowers covering the entire bush during its winter flowering season. It creates a buzz of activity attracting bees, butterflies and other insects to your garden.
Diosma prama is a finely leafy, single-stemmed, aromatic shrub with a rounded habit, growing to a height of 1.5 m.
Leaves are light green in colour, lanceolate, 1-5 x 0.5-2.0 mm, sessile (lacking a stalk) and alternately arranged on the branches and stems. Oil glands are found scattered towards the midrib of the leaf, and when the leaves are crushed, they release a sweet scent.
Small, white, star-shaped flowers are borne at the tips of branches and measure 5-8 mm in diameter. Flowers are either borne singly or in twos and are borne in abundance. Flowers can be found almost all year round but mainly from autumn to spring (March to September). Tiny, shiny black seeds are borne in a 5- chambered, horned capsule.
Diosma prama is distinguished from other Diosma species by its branches and petals that are hairless and the oil glands on its leaves that are scattered mainly towards the midrib. It is similar to D. ramosissima, and in the past D. prama has been mis-identified as D. ramosissima. However, D. ramosissima differs from D. prama in its branches, leaves and petals, which are covered in minute soft hairs (puberulous), and its oil glands, which are in rows either side of the midrib.
Least Concern (LC), Diosma prama is not threatened.
Distribution and habitat
Diosma prama naturally occurs in the Little Karoo, from the Touwsberg and Klein Swartberg to the Baviaanskloof Mountains. It is found in mountainous country on dry, stony or rocky sandstone slopes.
Derivation of name and historical aspects
The name Diosma is derived from the Greek dios, meaning 'divine', and osme, 'odour', in other words, 'heavenly scent', referring to the scent of the leaves when crushed. The specific epithet prama is a shortening of the unwieldy originally proposed name pseudoramosissima, meaning 'false ramosissima' , which indicates the confusion in identifying this species and its similarity to D. ramosissima.
The genus Diosma is comprised of 28 species found in the southern and southwestern Cape from the Cocksomb Mountain and from near Humandsorp in the east to the Cape Peninsula in the west and from Cape Agulhas in the south to near Nieuwoudtville in the north, with two outlying populations near Garies in Namaqualand. Diosma are distinguished by their small, less than 10 mm diameter flowers, spreading petals, and the conspicuous green disc overtopping the ovary. Also, the style and filaments are very short and do not exceed the petals, and it has vestigial or no staminodes. Diosma belongs in the Rutaceae and members of this genus are commonly and generally called buchu, bitter buchu, wild buchu or false buchu (boegoe, bitterboegoe or wildeboegoe in Afrikaans).
Diosma prama has a wide open flower and offers a cup of nectar, and the pollen ripens before the style lengthens: all of which indicate that it is pollinated by insects. At Kirstenbosch, this shrub is very popular with the bees, and attracts butterflies and other insects too.
Diosma prama does not coppice from the root, and would thus not survive to resprout after a fire. Seeds are borne in a capsule, but are not stored on the bush. On ripening, they are expelled from the capsule by a catapult mechanism. This is known as ballistic dispersal.
Diosma prama is a slow grower and best planted in a mixed fynbos border or planted as a filler plant towards the back, with smaller buchus such as Agathosma ciliaris, Acmadenia heterophylla, Adenandra uniflora, and colourful herbaceous perennials towards the front. It forms an interesting specimen when planted in a container and positioned in full sun on a patio or stoep. It is an excellent long-lasting cutflower that can be used like gypsophila. Lovely in bouquets because handling releases the sweet fragrance of the foliage.
Growing Diosma prama
Planting Diosma prama in your garden is best done during the autumn and winter season. It requires a position in full sun, with well-drained soil, compost and an annual layer of mulch. Buchus respond well to fairly dense planting, which helps to retain soil moisture.
Diosma prama can be grown from seed and cuttings. Seed are borne in a capsule from which they are expelled on ripening. This is known as ballistic dispersal. Fresh seed is sown in autumn. 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. Flowers are produced after two years.
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 (December to February). 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. Firmly place the cuttings in a medium of 50% bark and 50 % polystyrene. Ideally these cuttings should now be placed in a 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 7 to 8 months. Feed regularly with a well-balanced nutrient. Yellow leaves can be treated with an application of iron chelate.
Other interesting species are:
- Diosma acmaeophylla, commonly known as ribbokboegoe, grows to a height of 2.5 m. The leaves are linear and arched, flowers white to cream-coloured from July to January. Occurs naturally around Clanwilliam, Namaqualand and Matjiesfontein.
- Diosma ramosissima is a well-branched shrub, reaching a height of 1.5 m. Leaves are linear, dull blue-green, with a strong scent when crushed. Flowers white or greenish in colour from August to November. Grows naturally on either side of the Olifants River, in Namaqualand and near Worcester.
- 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.
- Raimondo, D. et al. 2009. Red list of South African plants. Strelitzia 25. SANBI (South African National Biodiversity Institute), Pretoria.
- Williams, I. 1975. Studies in the genera of the Diosmeae (Rutaceae): 6. J. S. Afr. Bot. 41(4):250-255
- Williams, I. 1982. Studies in the genera of the Diosmeae (Rutaceae): 14. A review of the genus Diosma L. Journal of South African Botany 48: 329-407.
Kirstenbosch National Botanical Garden
updated by Alice Notten, Kirstenbosch NBG, July 2017
Plant Type: Shrub
SA Distribution: Eastern Cape, Western Cape
Soil type: Sandy
Flowering season: Spring, Early Summer
Flower colour: Green, White
Aspect: Full Sun
Gardening skill: Average