Vernonia glabra is a strong-growing, herbaceous perennial that flowers throughout the summer, producing masses of flowers that look like little mauve paintbrushes, at the tips of many upright stems.

Description
From a woody rootstock, tall, robust stems shoot stiff and upright, branching sparingly to about 1.2 m high. Smooth to the touch, the leaves are bright green, linear (long and narrow), 60-120 x 15-25 mm, with a serrated edge and a prominent, light yellow, central vein. They alternate with each other along the stems, getting smaller towards the tip.

The flowers are grouped in dense clusters at the tip of the stems. The tight buds are light green to straw-coloured, opening into light and dark purple flowers, which turn into fluffy white seedheads. Flowering profusely throughout the summer and autumn, there are always buds, flowers and seedheads on the plant at the same time.

Distribution
Vernonia glabra occurs naturally in South Africa, where it is found in KwaZulu-Natal and Mpumalanga, as well as in Swaziland, Namibia, Tanzania and also Kenya, usually as a pioneer in disturbed ground.

Derivation of the name
The genus Vernonia is named after William Vernon (d. 1711), an English botanist who collected in Maryland in the late 1600's. The species name glabra is Latin and means smooth, referring to the smooth leaves.

There are more than a thousand species of Vernonia found in the warmer countries in the world, with about 40 species widespread throughout southern Africa, except in the south-western Cape.

Growing Vernonia glabra

The Vernonia glabra at Kirstenbosch was collected in northern KwaZulu-Natal near Kosi Bay. The original plants were found growing in recently burned grassland and were resprouting strongly, with no flowers but new growth perfect for cuttings.

The inspiration for collecting this vernonia was another species, Vernonia natalensis that has been growing at Kirstenbosch for many years. Vernonia natalensis is very striking with attractive silver-grey foliage in summer and masses of purple flowers at Christmas.

Vernonia glabra has much more vigour than Vernonia natalensis, but it took some time to show its value in the garden. By itself, the plants do not make much of an impact as the individual flower heads are small and the tall green stems can look untidy standing alone, but mixed into an herbaceous border it has proved to be one of the best plants for summer display. Planted with different Agapanthus species, Geranium multisectum, Aerva leucura, Lobelia valida, Orphium frutescens, Orthosiphon labiatus and Diascia personata, Vernonia glabra adds texture, height and splashes of colour from summer to autumn.

Vernonia glabra does best planted in full sun and well-composted soil with good drainage. It grows actively during summer and should be cut down in the middle of winter when it gets untidy and goes slightly dormant. The new growth shoots out in early summer and the plants get stronger year after year as the clumps get more established.

New plants are easy to propagate from cuttings made from the new growth throughout the summer. Cuttings usually root within a month and are ready for planting within 3 months. It is best to plant the young plant out early in summer to give them a long growing season to establish themselves before going dormant in winter. Established plants can also be divided. Vernonia glabra can also be propagated by seed sown in spring or early summer.

Other Vernonia species in Kirstenbosch are Vernonia natalensis, with its silver-grey foliage and purple flowers, that makes a beautiful display in the rockeries at Christmas time, and the striking, tall shrub V. myriantha that flowers in late autumn with big heads of mauve flowers.

Liesl van der Walt
Kirstenbosch National Botanical Garden
January 2003