Continuing our quest to explore the beauty and complexity of the plant kingdom, the Apocynaceae family occupies the spotlight this month.

The Apocynaceae family is also known by the common name ‘dogbane’. Initially dogbane was the name given to the plant APOCYNUM venetum because it was believed to poison dogs; this plant was allocated to the genus Apocynaceae by Dioscorides. (For those readers who, like me, didn’t know, ‘bane’ means ‘cause of ruin or poison’ in dictionary terms.) This huge family has around 215 different genera, comprising some 2 100 different species of lianes, trees, shrubs, perennial herbs and succulents. As is the case with all plant families, they are classified according to flower structure. Very simply, most flowers in this family have a calyx made up of five fused sepals and a corolla comprising five fused petals. Many of the species have fragrant flowers.

A number of the plants in this family contain glycosides and alkaloids that are toxic, often to the point that they are responsible for the deaths of humans. Certain extracts are used in commercial medicine, whilst some are used by traditional healers in different cultures. Included are some of our very own indigenous species: Acokanthera and Strophanthus. However, as this is a gardening magazine, it is best that we not dwell on the toxic and narcotic properties of the plants and rather take a closer look at some of the family that we recognise from gardens around the country. Suffice to say though, that you should never consume parts of any plant, whether they look edible or not, unless you are entirely sure of the plant’s identity and equally sure that the plant represents no danger.


Indigenous plants
Our indigenous flora, including some outstanding garden plants, is well represented in the Apocynaceae. ACOKANTHERA oppositifolia (common poison-bush) is an evergreen shrub or small tree that is smothered in clusters of sweetly-scented white flowers in winter and spring. CARISSA macrocarpa (amatungulu, big num-num or Natal plum) has lovely white flowers followed by red fruit. Various garden forms are available including ‘Green Carpet’ which is planted extensively as a tough and enduring ground cover, whilst the form with green and gold variegated leaves is useful in gardens. ADENIUM multiflorum (impala lily or Sabi star) and PACHYPODIUM saundersii (kudu lily) are indigenous succulents found in the drier areas of the eastern parts of the country. Both make for spectacular garden plants in the warmer, frost-free climates. Their clusters of tubular flowers in shades of white, pink and red really stand out. STROPHANTHUS speciosus (common poison rope) has rather strange looking, spidery flowers in shades of creamy-yellow with an orange centre, which are borne in spring and early summer. The flowers are highly scented.

Climbers and ground covers
Free-flowering climbers and ground covers are always popular garden ornamentals. The dogbane family includes some real gems that are revered worldwide. BEAUMONTIA grandiflora (Nepal trumpet vine) has huge white flowers and large leaves and can often be seen climbing to the upper reaches of large trees in older, suburban gardens. MANDEVILLA laxa (Chilean jasmine), MANDEVILLA x amabilis hybrids, and MANDEVILLA sanderi hybrids (also known as Dipladenias) are probably amongst the most floriferous and rewarding of all garden climbers. The tubular flowers adorn the plants from spring to autumn in shades of white, pale pink, rose pink and red. TRACHELOSPERMUM jasminoides (star jasmine) is grown both as a climber and ground cover, and produces masses of little, white, star-shaped flowers in late spring. Star jasmines are not only pretty, but also hardy and enduring, and thus planted extensively all around the country. VINCA major and VINCA minor (periwinkles) are popular ground covers for shade, especially in the colder regions. Their flowers are usually blue or white and some garden cultivars have attractive variegated foliage.

Ornamental trees
Generally the garden trees in this family are rather small and suitable for suburban gardens in frost free areas. Some are indigenous whilst others originate from foreign shores. PLUMERIA rubra (frangipani) is prominent in gardens all along the coast. They bloom in a huge array of colours, from snow white to almost black, and are highly decorative. RAUVOLFIA caffra (quinine tree) is indigenous, with glossy green leaves and small white flowers in clusters. The shiny green seeds ripen to black, attracting many birds to the garden. STEMMADENIA bella is an especially attractive small tree producing scented white flowers amongst its glossy green foliage. TABERNAEMONTANA elegans and T. ventricosa (toad tree) occur naturally in coastal or riverine forests along the east coast of Africa. Both have sweetly-scented white flowers and unusual fruit or seed pods produced in joined pairs.

Shrubs
Shrubs are an integral part of the permanent structure of the garden. The dogbane family includes the genus Allamanda, a group of pretty flowering shrubs that flourish in warm sub-tropical climates. Most have yellow, trumpet-shaped flowers that appear in summer and autumn in great abundance. ALLAMANDA blanchetii has purple or mauve flowers and always makes for a spectacular show. PACHYPODIUM lamerei (Madagascar bottle tree) and the similar looking P. geayii are succulents with thickly swollen stems covered in silvery-grey thorns. Beautiful white flowers appear from the branch tips in summer. They are popular feature plants in frost free gardens and also superb container plants for outdoors (and are sometimes even used indoors).

Some are classified as invaders
As always it is important to mention the plants that are currently declared as alien invaders in this country. CATHARANTHUS roseus (Madagascar periwinkle) in its weed form is common in disturbed areas along the coast and in the sub-tropical zones, however, certain garden hybrids are still planted extensively in ornamental horticulture. Extracts from this plant are used in the treatment of various forms of cancer. NERIUM oleander (oleander) is infamous for its toxic properties and the single flowered forms that produce fertile seed are declared alien invader plants and may no longer be planted in gardens. However, certain double flowered sterile hybrids are still grown as garden plants. THEVETIA peruviana
(yellow oleander) is a declared invader and all parts of the plant are poisonous.

New additions
Recent changes to the botanical classification of this family has seen the Asclepiadaceae (carrion flower family) and Periplocaceae (khadi-root family) being included in the Apocynaceae family, necessitating the creation of subfamilies, namely Apocynoideae, Asclepiadoideae and Plumerioideae. This article only covers the former classification and does not include these amendments.