Agathosma martiana Sond.
Common names: Humansdorp buchu (Eng.); Humansdorp boegoe (Afr.)
A hardy, white-flowering, aromatic shrub for the fragrance, buchu or fynbos garden.
This a variable shrublet from 0.6 m to a large shrub of 3 m tall. It grows from a single stem at the base to produce a rounded, leafy shrub. The entire bush is covered in small, dark green, ovate, sharply mucronate leaves, which emit a foul, acrid smell when crushed. Several white flowers tinged with maroon dots are borne in terminal clusters, from midwinter to spring (July to September). The fruit is a 3-chambered capsule.
This species has been accorded a Least Concern status (LC) according the SANBI Red List of South African Plants.
Distribution and habitat
Agathosma martiana has a limited distribution range on the lower mountain slopes around the Humansdorp area in the Eastern Cape Province of South Africa.
Derivation of name and historical aspects
The genus name Agathosma is derived from Greek words, agathos and osme, which means ‘good’ and ‘scent’ respectively, in reference to the aromatic scents present in the leaf glands. The presence of aromatic oil glands in the leaves is characteristic of all members in the family Rutaceae. The specific epithet martiana is in reference to the famous German botanist and explorer, Karl Friedrich Philipp von Martius (1794–1968). He served as keeper and botanist at the Munich Botanic Garden.
The Rutaceae, also known as the buchu or citrus family, is of relative economic importance and is well known for its variety of citrus. The family is common throughout temperate and tropical regions of the world, in particular Australia and South Africa. The 160 genera comprise of some 1 650 species.
Southern Africa is home to 21 genera and 301 species and includes the genera Calodendron, Zanthoxylum, Vepris, Acmadenia, Agathosma and Adenandra. The South African species belong in the subfamily Diosmeae. Species in this particular subfamily are shrubs with simple leaves and unique fruits made up of 1–5 free carpels characterized by horn-like processes at the apex. The carpels undergo a complete separation at maturity, when each carpel splits down an inward-facing line. The seeds are subsequently released in an extremely powerful manner because of the hygroscopic properties of the inner layer of the wall.
The highest diversity of species in South Africa, including Agathosma, is concentrated in the Western Cape. Agathosma is made up of approximately 150 species of evergreen, large to small shrubs, with flowers anything from usually purple, pink or white. Agathosma replaced Barosma as the name for the genus.
Bees and butterflies have been observed visiting this species and they are potentially some of the pollinators.
No medicinal or cultural uses have been recorded. This hardy species is a welcome addition for the mix fynbos garden.
Growing Agathosma martiana
Sow the seed in autumn, in a light, well-draining medium. Cover the seed with a thin layer of sand or fine compost. Seeds that are treated with smoke show improved germination: sowed trays can be subjected to a gaseous smoke-treatment, or the seeds can be soaked in a liquid smoke solution prior to sowing. The seed trays are then watered and moved to a space that provides good light and ventilation. Seeds must not be allowed to dry out completely and should also not be overwatered. Germination takes between 1–2 months and the onset of the first 4 true leaves, is an indication of the readiness of the seedling to be transplanted.
All potted seedlings now get moved to slightly shady areas to allow for hardening off for roughly 3–4 weeks. Thereafter, plants get moved into the full sun. This is also a moment to encourage more vigorous bushy growth, through the pinching out of the growing tips of the young seedlings or rooted cuttings.
Good results are also being yielded through the propagation of cuttings, using tip or semi-hardwood cuttings using fresh material of the current year’s growth. Prepare cuttings of 25–40 mm long, remove about a third of the foliage and cut it below the node. Dip the cuttings in a rooting hormone, firmly position it into ready-made holes with the rooting medium (equal parts fine-milled bark and perlite) and placed in the cutting tray on a mist-unit with heated benches. Rooting of the cuttings will take 9–11 weeks. Rooted cuttings are subsequently moved to a hardening-off section for 2–3 weeks.
Pot the rooted cuttings in to a well-drained soil mix and place in a shady area for 2–4 weeks to harden off and move into full sun, following this period. After the next 7–8 months plants will be ready for planting out in the garden.
The Humansdorp buchu is fine-leaved medium to large shrub, perfectly suited for a mixed fynbos, renosterveld or fragrance garden. The dark green leaves will contrast well with the different shades of brown from some restios or phylicas, the greys of a Helichrysum or Salvia, other varieties of green and some medium to coarse leaf textures.
This species can be grown with companion plants which might include: Thamnochortus cinereus, Caprobrotus edulis, Pelargonium suburbanum, P. peltatum, P. betulinum, Protea cynaroides, Coleonema pulchellum, Metalasia aurea, Dimorphotheca ecklonis, Agathosma capensis, A. mucronulata, A. ovata, Phylica ericoides, Chironia baccifera, Metalasia muricata, Searsia crenata, S. lucida, Passerina corymbosa and Felicia echinata
Plant Agathosma martiana in a sunny position that drains well at the beginning of the rainy season. This will allow enough time for it to get established in the garden, before the onset of the warmer spring and summer months. Planting can be done fairly close together, allowing for spaces of 20–30 cm, just enough to encourage growth. Buchus prefer denser plantings, as this aid in moisture retention. Generous mulching will further enable moisture retention. Cut plants back very lightly after flowering.
- Charters, M.L. 2006–2016. The Eponym Dictionary of South African plants. Published online at http://www.calflora.net/southafrica/1Titlepage.html
- Eksteen, J. 2022. Observation of Agathosma martiana, Baviaans Local Municipality, Eastern Cape. iNaturalist. Online. https://www.inaturalist.org/observations/127634028.
- Gould, M. 1992. The buchus: cultivation and propagation. National Botanical Institute, Cape Town.
- Koekemoer, M., Steyn, H.M. & Bester, S.P. 2015. Guide to Plant Families of southern Africa. Strelitzia 31. 2nd ed., 2nd print. South African National Biodiversity Institute, Pretoria, South Africa.
- Lucas, N. 2008. Agathosma apiculata G. Mey. Dummer (Rutaceae). PlantZAfrica. Online. http://pza.sanbi.org/agathosma-apiculata.
- Lucas, N. 2008. Agathosma capensis (L.) Dummer (Rutaceae). PlantZAfrica. Online. http://pza.sanbi.org/agathosma-capensis.
- 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.
- Oliver, R. 2019. Agathosma orbicularis (Thunb.) Bartl. & H.L.Wendl. (Rutaceae). PlantZAfrica. Online. http://pza.sanbi.org/agathosma-orbicularis.
- Raimondo, D., Von Staden, L., Foden, W., Victor, J.E., Helme, N.A., Turner, R.C., Kamundi, D.A. & Manyama, P.A. (eds) 2009. Red list of South African plants. Strelitzia 25. South African National Biodiversity Institute, Pretoria.
- Sonder, W.O. 1860. Rutaceae. Flora capensis Volume 1:369-442. Accessible via Biodiversity Heritage Library https://www.biodiversitylibrary.org/item/15231#page/472/mode/1up.
- Wikipedia, Carl Friedrich Philipp von Martius. https://en.wikipedia.org/wiki/Carl_Friedrich_Philipp_von_Martius. Accessed 13/08/22.
Kirstenbosch National Botanical Garden
Acknowledgements: the author thanks Johan Eksteen (aka strandloper) for allowing the use of his images to illustrate this article.
Plant Type: Shrub
SA Distribution: Eastern Cape
Soil type: Sandy, Loam
Flowering season: Spring, Winter
Flower colour: Purple, White
Aspect: Full Sun
Gardening skill: Average