Download Article 56 Cestrum - Botanical Society of South Africa

Weeds in our Area (Part Fifty Six)
By Bob and Ena McIntyre – Garden Route Branch.
Cestrum sp.
This week’s subjects have featured very prominently in the Gardening books over the years. They
have been noted for their hardiness, ability to withstand tough drought conditions, quick growth,
easy to propagate either from seed, cuttings or root division, their ability to thrive in poor soils and
of course the array of pretty, brightly coloured flowers. Cestrum aurantiacum, C.elegans (yellow
and crimson cestrum) and C.laevigatum are members of the Solanaceae family. C.laevigatum
shares a common name (inkberry) with the Phytolacca sp that we covered in Part 54, illustrating
why confusion often reigns when using common names as the plants are in fact completely
different in appearance – in this case the only similarity lies in the colour of the berries. Introduced
as ornamental shrubs from Central, South America and Mexico all have become problematic.
C.laevigatum (illustrated) is a particularly serious problem along our southern and eastern shores
and even into the central parts of the country.
Identification:
Cestrum
aurantiacum
and
C.laevigatum are both evergreen shrubs of similar
height (1 – 2m), with stems and leaves that bruise
easily. The leaves are large, (130 X 70, 150 X 50
respectively) elliptic in shape and light green in
colour. C. aurantiacum bears orange-yellow flowers
and C.elegans purple-pink flowers. Cestrums all have
the characteristic tubular flowers that are borne in
large closely-packed clusters at the ends of the
branches.
Invasive Status:
Cestrum aurantiacum and
C.laevigatum are both declared weeds (Category 1
and should therefore be eradicated). Both are special
effect weeds that are competitive, poisonous and
transformers. These plants invade forest margins, savanna, grassland, rivers, plantations and
coastal dunes.
Control: Cestrum aurantiacum does not have a herbicide registered and manual control, i.e. hand
pulling of seedlings or removal of the entire plant in mature specimens will be the best solution.
Timbrel 3A with active ingredient triclopyr is registered for combating C.laevigatum.
Indigenous substitutes: Anisodontia capensis (Wild hibiscus),Bauhinia tomentosa (Bush neat’s
foot), Burchellia bubalina (Wild pomegranate) and Polygala myrtifolia (Septemberbossie).
References: “ALIEN WEEDS AND INVASIVE PLANTS” : Lesley Henderson. Copyright © 2001
Agricultural Research Council. Poisonous Plants of South Africa: Ben-Erik van Wyk et al.
Ornamental Shrubs and Trees for gardens in Southern Africa: Una van der Spuy, The A-Z of
Gardening in SA: W.G. Sheat, Flowering shrubs and Trees for SA Gardens: Sima Eliovson