Plectranthus laxiflorus Benth.
Common names: citronella spurflower (Eng.); sitrinella spoorsalie (Afr.); ubebebe (isiXhosa)
An erect, easy-to-grow, aromatic, herbaceous shrub with decorative, light green foliage, suitable for planting in humid, moist and slightly shaded areas in frost free gardens.
Plectranthus laxiflorus is a freely-branched, hairy, aromatic perennial, with climbing to spreading stems that form roots at lower nodes, where they touch the ground. It is a soft, herbaceous plant with a growth habit that can be erect or decumbent (lying on the ground) and grows to a height of 300–600 mm. The leaves are oppositely arranged along the stem, ovate to deltoid, and 60–100 × 40–60 mm, pubescent, corrugated, with pink to red glands. The base of the leaf is cordate; the petiole is 25–80 mm long; the apex is acute and the margins dentate, with 16–20 or more pairs of teeth.
The inflorescence consists of a loose terminal raceme up to 300 mm long. The flowers are small, white, frequently with pale mauve-brown stripes on the upper lip. The corolla is 12–14 mm long, the corolla tube bent abruptly downwards (deflexed), enlarging towards the throat. The calyx is 3.5–4.0 mm long, enlarging to 8 mm after flowering. The fruit is a brown nutlet, 1.5 mm long. Flowering time is autumn into winter (March to June).
The leaves have a particular fresh citronella-like scent, one of a kind among the South African plectranthus, and can be allergenic to some people, causing skin irritation.
Plectranthus laxiflorus is not threatened; it is considered as Least Concern (LC) on the Red List of South African plants.
Distribution and habitat
Plectranthus laxiflorus is widely distributed in southern and eastern Africa, it occurs from east of the escarpment near Humansdorp in the Eastern Cape, in semi-coastal regions, northwards through the Wild Coast and KwaZulu-Natal midlands, to Mpumalanga and Limpopo, and in Swaziland and northwards into tropical Africa. It is abundant in damp spots, along streambanks, on forest margins and in clearings of mist-belt vegetation, where summer precipitation ranges from 700 to 2 000 mm per annum.
Derivation of name and historical aspects
The name Plectranthus is derived from the Greek plektron, meaning ‘spur’ and anthos, which means ‘flower’; referring to the spur that is found at the base of the corolla tube of the type species for the genus, P. fruticosus, and the reason for the common name spurflower. The specific epithet laxiflorus comes from Latin and means ‘loose-flowered’, referring to the lax arrangement of the inflorescence.
It was first collected at the Mzimvubu River near Port St Johns in 1832, by Johann Drège, and was introduced to Kirstenbosch National Botanical Garden in 1920 by Carnegie from Pietermaritzburg.
There are 350 Plectranthus species, which are widely distributed in Africa, India and Australia, with 53 species found in South Africa and Namibia. The South African species with the greatest horticultural potential are found from the Eastern Cape to KwaZulu-Natal.
Similar to most species of Plectranthus, P. laxiflorus does well in shady areas. The short-tubed flowers attract insects, such as honey-bees, butterflies, bumblebees and bombyliid flies, which pollinate them.
Plectranthus laxiflorus leaves are used in traditional medicine to treat colds and stomach illnesses. Although not a very showy species, it is grown for its citronella scent and it is a great filler in shaded and semi shaded areas of the garden, but is best planted in the middle of the bed to prevent skin contact with the leaves, which may cause irritation.
Growing Plectranthus laxiflorus
Plectranthus laxiflorus is easily propagated from cuttings but can also be propagated from seeds. When propagating from cutting prepare a well-drained rooting medium of sifted bark, compost and river sand (1:1:1). Take tip or stem cuttings, preferably in spring or summer, in the morning or evening when the plant is at its most vigorous and choose a plant that is free from pests and disease. Soft tips root quicker than semi-hardwood growth, however both root effectively. Cuttings are best 60-100 mm long with 3 or 4 nodes. Make the cut just beneath a node. Place them in sand, perlite, vermiculite or peat, or any blend of these, keep them damp and shaded and they should root in 2-3 weeks. Sow seeds in well-drained soil, in spring, spread softly with a thin layer of sand and place in a warm. yet shaded area. The seed germinates in around 3 weeks.
Like other species of Plectranthus, P. laxiflorus does not require much care but it is advisable to prune during late winter, after flowering, to keep its growth neat, maintain vigour and maximize flowering. Feed with compost and water well for fast growth. They perform best in a shady, well-watered, frost-free site.
There are not many pests that attack P. laxiflorus, however whiteflies, aphids and mealybugs have been seen causing damage on plants growing in a controlled environment, such as a glasshouse.
- Codd, L.E. 1985. Lamiaceae. Flora of southern Africa, Vol. 28, 4. Botanical Research Institute, Department of Agriculture and Water Supply, Pretoria.
- Harvey, W.H. 1811–1866. Flora capensis: being a systematic description of the plants of the Cape Colony, Caffraria, & Port Natal (and neighbouring territories) Volume 2.
- Tropical Plants Database, Ken Fern. Accessed 2019-05-30. http://tropical.theferns.info/viewtropical.php?id=Plectranthus+laxiflorus
- Van Jaarsveld, E. 2006. The southern African Plectranthus and the art of turning shade to glade. Fernwood Press, Vlaeberg, Cape Town.
- World Flora Online, Plectranthus laxiflorus Benth. Accessed 03/06/2019. http://www.worldfloraonline.org/taxon/wfo-0000275567.
Thandisizwe Siphenkosi Ndabeni and Mpendulo Gabayi
Kirstenbosch National Botanical Garden
Plant Type: Perennial, Shrub
SA Distribution: Eastern Cape, KwaZulu-Natal, Limpopo, Mpumalanga
Soil type: Sandy, Loam
Flowering season: Autumn, Winter
PH: Acid, Neutral
Flower colour: White, Mauve/Lilac
Aspect: Shade, Morning Sun (Semi Shade), Afternoon Sun (Semi Shade)
Gardening skill: Easy