Tough beauties

Sunday, 21 February 2016

Catharanthus roseus

This summer I have had success growing a pretty and tough-seeming annual sometimes called the Madagascar periwinkle (or vinca) Catharanthus roseus. It has simple, flat flowers usually white, purple or pink, and enjoys our hot, humid summers, not wilting even on the most challenging days. It has been around in Sydney gardens for a long time, often regarded as fairly common, but in line with my current philosophy to go more for undemanding plants, I plan to grow it again next year and to seek out other flower colours: I have seen a lovely deep purple one in the garden of a friend, and some are bicoloured with a distinct 'eye'. Another plant that has been around forever in Sydney gardens is 'chain of hearts' (Ceropegia linearis, pictured at the start of the next paragraph): I remember it growing in a hanging basket on the porch of my parents' house many decades ago, with amazingly long pendulous stems bearing mottled silvery-grey leaves that really are shaped like hearts. I have recently been given a plant, which I plan to grow in a hanging basket myself in a semi-shaded spot. And I've just discovered that the Madagascar periwinkle and the chain of hearts in fact belong to the same interesting plant family, the Apocynaceae.

Ceropegia linearis

The family Apocynaceae contains around 410 genera, most of which come from tropical and semi-tropical parts of the world, including Africa, South and Central America, and India. The flowers of the plants are in the main simple and flat, like my Madagascar periwinkle, but they are often large and brilliantly coloured; many have a fleshy texture to them. The foliage of the plants is in many cases lush and glossy. They range from trees down to annuals. And lots of these plants do really well in Sydney gardens without requiring much cosseting, adding an exotic look.

Trachelospermum jasminoides

There are a number of climbing plants in the family, and the most familiar in Sydney is the star jasmine (Trachelospermum jasminoides), with its glossy leaves and deliciously scented white flowers in late spring. Perhaps it is all too ubiquitous these days, but this vine has the advantage of growing and blooming so very well in shady parts of the garden, and can also be used as an effective groundcover plant. A variegated version has white and pink-splashed foliage. Another vine for shade in the family is alluring Hoya, with its clustered waxy flowers that look almost unreal.

Mandevilla sanderi at The Boat House, Palm Beach, Sydney

Other climbers in the family that do well in Sydney include Mandevilla sanderi (syn. Dipladenia sanderi cultivars, with flamboyant funnel-shaped flowers of pink, white or red, which bloom almost all year round and can be grown in a large pot; Stephanotis floribunda (now renamed Marsdenia floribunda!) with white fragrant bell-like flowers; and the giant Beaumontia grandiflora with its simply enormous white trumpets. There is a wonderful specimen of Beaumontia festooning the fence near the Friends' Nursery in the Royal Botanic Garden Sydney. Though needing some sun for good flowering, these vines prefer a little shelter during the hottest part of the day in summer.

Carissa macrocarpa

The frangipani trees (Plumeria rubra) that adorn many old Sydney gardens also belong to the Apocynaceae family. There are so many gorgeous colour variations of these available these days and they are still in full bloom at the moment. On a smaller scale, shrubby Carissa macrocarpa (the Natal plum) is another example, and it is sporting its clear white flowers now. It is one of the toughest shrubs in my garden, growing at the top of my long battleaxe driveway in a dry position that is never watered. It forms a rounded evergreen mound, and is rather spiny, being said to make a good front hedge to deter burglars.

Oxypetalum coeruleum

A small shrubby perennial that is sometimes seen in Sydney gardens is the stunning blue-flowered Oxypetalum coeruleum (syn. Tweedia coerulea). It seems to do best in the Hills area, with colder winters and less humidity in summer: in one garden I know, it has self-seeded gloriously. I have never had great luck with it as it tends to rot off in summer, but I am going to try it again in early spring with some seeds from the garden where it does so well, and treat it as an annual in a sunny dry spot.

Vinca major Variegata in the garden of Alida Gray in Sydney

Vinca major and Vinca minor are groundcovers from Europe that belong to the family. I have an uneasy relationship with these plants as they can have a tendency to take over; however, they are useful for a dry shady area where other plants won't easily grow, and the variegated version can look very effective under trees (as illustrated at left). The pretty blue (or less commonly pink, white or plum) flowers appear in spring.

Most members of the Apocynaceae family exude a milky sap when the stems are cut or injured. Indeed, the sap of some genera was used as a rubber substitute in World War II when supplies of natural rubber were cut off. In some cases, the sap is quite toxic, and was used on poison arrows in some cultures. The tough old shrub called oleander Nerium oleander is a well-known poisonous member of the family. Handle all these plants with care. Some Apocynaceae plants were used in traditional medicines, and today, Catharanthus roseus is showing promise as a source of a drug for treating cancer.