Chaenostoma cordatum (Thunb.) Benth.
Common names: Trailing phlox (Eng.)
Chaenostoma cordatum is the ideal groundcover for that garden spot with varying microclimates. Performing equally well in full sun to shady conditions and in coastal or inland places, it could be the answer to many a gardener's prayer: "Just let something [indigenous] grow in that empty patch, please."
This evergreen, perennial herb varies in height from ground-hugging to about 300 mm. Spread is approximately 300-500 mm. The stalked, dark green leaves are borne in opposite pairs and are usually ovate to broadly ovate. Both leaf surfaces are slightly hairy and the leaf-margins are minutely toothed.
Single, stalked flowers appear in the axils of leaves almost all year round in warm areas. The small, green calyx is 5-lobed. The corolla is fused at the base into a short, funnel-shaped, yellow or orange tube. Beyond this the lobes spread out and form a small, star-shaped flower. It has one pair of stamens exserted and one pair included in the tube. The fruit is a capsule with amber seeds.
Chaenostoma cordatum (= Sutera cordata ) has often been confused with C. pauciflorum (= S. pauciflora ). C. cordatum can easily be separated from C. pauciflorum because of differences in the stems, leaves and calyces, colour of the corolla and branches.
Chaenostoma cordatum is not threatened.
Distribution and habitat
This species is found from George in the southern Western Cape to East London in the Eastern Cape, with the possible exception of the Algoa area. It appears not only along coastal stretches but also inland in areas such as forested kloofs from the Outeniqua Mountains around George to Grahamstown. It is also found in various forms of scrub & kloof-margins. In altitude it ranges from sea level to about 1000 m.
Derivation of name and historical aspects
Chaenostoma means gaping mouth, while cordatum refers to the more or less heart-shaped leaves.
Thunberg initially named it Manulea cordata in 1800 but it was re-named Chaenostoma cordatum in 1836 by Bentham because of the basal corolla tube and bell- or funnel-shaped throat. He become aware of Sutera by 1846 and used both as separate genera. In 1891, Kuntze changed the name to Sutera as he thought the two genera were the same. Hilliard in 1994 used Sutera but had two sections, Sutera and Chaenostoma, within this genus. Sutera was kept until 2005 when Swedish botanists, Per Kornhall and Birgatta Bremer, decided through DNA-sequencing that there is enough evidence for these genera to be separated. They reverted to the previous name, Chaenostoma, for the group of the species including C. cordatum. It is sometimes referred to as Bacopa but it is not certain where the use of this name originated.
This prostrate species with its white flowers and unmistakable yellow centre is most likely to be pollinated by bees.
No records have been found of this species being used for any medicinal purpose although it is used in horticulture.
Growing Chaenostoma cordatum
The fine textured leaves, the white flowers borne virtually all-year round and its broad range of habitats make this quick-growing perennial an extremely useful bedding plant. It also performs very well in rockeries, hanging baskets and window boxes. In the landscape-industry, where it is (still) known as Sutera and Bacopa, it is creating quite a buzz with numerous cultivars already developed or in the development process. Some of the cultivars include: Sutera 'Snowstorm': Large flowers and a more compact habit; Sutera ' Blue Showers': Lilac to pale blue flowers; Sutera 'Lavender Showers': Pale lavender star-shaped flowers.
This species is easily propagated. Sow the seed in a 1:1 mixture of fine bark and coarse river sand during the spring. Lift and replant rooted stems or take stem cuttings, preferably in summer and autumn. Use well-draining media such a 1:1 mixture of fine bark and river sand or 1:1 fine bark and polystyrene. Cuttings must be placed in a mist-unit, where rooting will occur in 2-3 weeks. (Use a plastic bag to make a mini-greenhouse if you have no mist unit.)
C. cordatum requires a free draining soil and is adaptable to sun and shade. During the heat of summer it will probably require additional moisture to continue flowering. It is sensitive to frost and not particularly drought tolerant. It is relatively pest-free, but white flies can occasionally be encountered. Treat these with an insecticide specific for these insects.
Acknowledgements Many thanks to Shirley Smithies at the SANBI National Herbarium for her review and contribution towards this article.
- Brickel, C. 1989. Royal Horticultural Society Gardener's Encyclopedia of plant & flowers. Dorling Kindersley Limited, London.
- Hilliard, O.M. 1994. The Manulea. A Tribe of Scrophulariaceae. Edinburgh University Press, Edinburgh.
- Joffe, P. 1993. The gardener's guide to South African plants. Tafelberg Publishers, Cape Town.
- Kirsten, K. 2004. A Gardener's Encyclopedia. Briza Publications. Pretoria.
Pretoria National Botanical Garden
Plant Type: Ground Cover, Perennial
SA Distribution: Eastern Cape, Western Cape
Soil type: Sandy, Clay, Loam
Flowering season: Sporadic/All year
Flower colour: White
Aspect: Full Sun, Shade, Morning Sun (Semi Shade), Afternoon Sun (Semi Shade)
Gardening skill: Easy