Gardening in the Western Cape

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Cape Agulhas Dune Fynbos - Overberg. Picture courtesy South African Tourism. Visit their flickr pageCape Agulhas Dune Fynbos - Overberg. Picture courtesy South African Tourism. Visit their flickr pageThe beautiful Western Cape draws millions of visitors each year, and foreign investors are snapping up valuable properties in the Province. For many South Africans it’s a favourite holiday destination, with many even moving to the Province to retire or seek a better quality of life.

Bordered by two oceans - the warm Indian Ocean to the south and the cold Atlantic to the west - The Western Cape Province is truly diverse in its beauty - from the wild Cape Agulhas coast with its sparse, sweeping stretches of sand, punctuated only by rocky outcrops and solitary fishing villages; to the sun-drenched vineyards of the Cape Winelands, and the magnificent Garden Route with its emerald lakes and indigenous forests. Even the magnificent passes which reach into the interior; and the wide and arid, windswept spaces of the Klein Karoo, seem part of a fantasy landscape that often defies description. 

12 Apostles & Camps Bay. Picture courtesy Christopher Griner. Visit his flickr page.12 Apostles & Camps Bay. Picture courtesy Christopher Griner. Visit his flickr page.The challenge of developing a coastal garden in the Cape has often deterred even the most resolute of home owners. Often faced with impoverished soils at the coast and at times severe summer drought, the amateur and even knowledgeable gardeners often struggle to secure plant cover which is hardy and yet at the same time functional. The Western Cape Province is exceptionally topographically and climatologically diverse, with many distinct micro and macroclimates, created by the varied topography and the influence of the surrounding ocean currents. Because topography and climatic statistics can vary greatly over even short distances, this can pose many problems for gardeners, unless you understand the subtle nuances of your particular region.

Worcester Karoo Flowers. Picture courtesy South African Tourism. Visit their flickr page.Worcester Karoo Flowers. Picture courtesy South African Tourism. Visit their flickr page.In summer the climate is influenced by westerly winds originating from a high-pressure system originating in the Atlantic Ocean and which settles semi-permanently over the southern and western parts of the country. The cold northward-flowing Benguela Current not only cools the west coast considerably but also contributes to the dryness and stability of the atmosphere. During winter cold polar air moves over the southwestern, southern, and south-eastern coastal areas, sometimes reaching the southern interior of the country from the southwest. These polar masses are accompanied by cold fronts as well as by rain and snow.

Most of the province is considered to have a typical Mediterranean climate with mild, wet winters, and warm, dry summers with very little rainfall. Thunderstorms are generally rare in the province (except in the Karoo), and extremes of heat and cold are common inland, but rare near the coast. Snow is a common winter occurrence on the Western Cape Mountains occasionally reaching down into the inland valleys. Otherwise, frost is relatively rare in coastal areas and many of the heavily cultivated valleys. Both the Great Karoo and Little Karoo in the interior have an arid to semi-arid climate, typified by many species of succulents and drought-resistant shrubs and thorn trees; with cold, frosty winters and hot summers with occasional thunderstorms.

Camps Bay. Picture courtesy Warren Rohner. Visit his flickr page Camps Bay. Picture courtesy Warren Rohner. Visit his flickr page From spring to late summer a strong, often persistent and dry south-easterly wind blows on the South African coastline. Although the wind blows over a wide area of the Western Cape Province, it is especially notorious in and around the Cape Peninsula, where it can be unpleasantly strong and irritating. Capetonians also call it "The South-Easter" or “The Cape Doctor” because of a local belief that it clears Cape Town of pollution and 'pestilence'. The South Easter is usually accompanied by fair weather. However, if the South-Easter is accompanied by a cut-off low as occasionally happens in the spring and autumn months, this can cause heavy rains to fall over the Western Cape. This phenomenon is popularly known as a “Black South-Easter”. The Laingsburg flood of January 1981 was caused by heavy rains as part of a black South-Easter. However, meteorological records for Cape Town show that the north-westerly winds of winter can be far stronger than the South-Easter, and these winds are usually accompanied by rain, which can fall for days and even weeks.

The hottest month of a typical year in the Western Cape is the month of February, but during March and April the weather of the region becomes idyllic as the summer heat subsides and the wind settles down.

Mossel Bay. Picture courtesy Bob Adams. Visit his flickr pageMossel Bay. Picture courtesy Bob Adams. Visit his flickr pageThe province is divided into three rainfall regions:  Winter Rainfall Region; Year-round Rainfall Region; Late-summer Rainfall Region. The winter rainfall region covers the western half of the Province, including Cape Town and the west coast, and cold fronts are the major rain-producing system in this region. The late-summer rainfall area includes the region around Beaufort West which receives most of its rainfall from late summer thunderstorms that occur between March and May. The year-round rainfall region includes most of the south coast, and Mossel Bay in the Garden Route is considered to have the second mildest climate worldwide after Hawaii. This region receives rain when an onshore wind pushes moist air inland and up against the mountains in summer and from cold fronts in winter. This region also commonly experiences thunderstorms which develop over the interior and then move towards the coast.

View of the Langeberg. Picture courtesy Atelier Design Studio. Visit their flickr page.View of the Langeberg. Picture courtesy Atelier Design Studio. Visit their flickr page.The Overberg, literally over the Hottentots-Holland Mountains, via Sir Lowry’s Pass, is a region of such immense beauty that it attracts thousands of visitors each year to its forests, orchards, grain fields, and vistas of rolling mountain ranges. This great expanse of beautiful and diverse landscapes stretches from the Hottentots-Holland Mountains in the west, to Swellendam in the east; and in the north it reaches as far as the Riviersonderend Mountains and south to include an incredible coastline. The Overberg is known as a gateway to the Garden Route coastal stretch, and both regions have a maritime climate with extremely lush vegetation with cool, moist winters and mild, moist summers. In its temperate rainforests (or Afromontane Forests), grow typical hardwood species of exceptional height, such as Yellowwood, Stinkwood and Ironwood trees, and these forests  cover many areas adjacent to the coast, reaching inland in deep river valleys and along the southern slopes of the Outeniqua mountain range.

Temperatures also vary greatly in the Province, near the coast the summer temperature rises from a pleasant low of 15° C in the morning to a pleasantly warm 27° C, and inland the temperatures are some 3 to 5° higher. Coastal winters see the mercury dropping to a mild 7° C at night and rising to a comfortable 18° C by day. Inland, the temperatures rise in the morning, from 5° C to approximately 22° C by midday. The Garden Route has a temperate climate with warm summers and mild winters, with gentle, intermittent precipitation. In winter the peaks of the Boland and the Cederberg Mountains are capped with snow, but with the onset of spring, the fast-retreating winter and summer sun, brings forth some of the world's most spectacular wild flower displays.

Franschoek. Picture courtesy Darren Glanville. Visit his flickr pageFranschoek. Picture courtesy Darren Glanville. Visit his flickr pagePerhaps the most critical factor in developing a garden in the Western Cape is the soil factor, as soils are of absolute importance in maintaining plant growth and survival. The evolution of plants in the Cape has been governed by two vital soil factors. Number one is whether the soil is calcareous or not. The second is how wet the soil becomes during the rainy months and how freely it drains. If you know what your soil type is, you will be able to determine, to a large extent, which plants it is likely to support.

If you live close to the sea on the West coast, on False Bay or along the stretch from Hermanus to Cape Agulhas, and all the way to Port Elizabeth, your home has most likely been built on dune sand. Coastal dunes are highly calcareous, that is, they are rich in calcium, a chief component of lime, largely due to their origins from finely broken pieces of marine shells. This type of soil has a high pH and is alkaline. It also contains small quartz grains and only small amounts of organic matter, and is therefore poor in plant nutrients like nitrogen and potassium. This type of soil is hard to amend, so it is better to introduce indigenous plants which thrive on such soils.

Bettys Bay, Harold Porter Botanical Garden. Picture ourtesy Allan Watt. Visit his flickr page.Bettys Bay, Harold Porter Botanical Garden. Picture ourtesy Allan Watt. Visit his flickr page.If you live inland of the Betty’s Bay coast and many parts of the Cape Peninsula, your soil is probably derived from sandstone or even granite. These soils have low calcium content with a low pH, and are therefore acidic. Although granitic soils have a better texture and a browner colour due to the presence of clay minerals, and are slightly more fertile than those developed on sandstone, they are still low in the all-important nutrients for good plant growth.

An easy scientific method to determine if your soil is calcareous or not is to dilute one part battery acid with nine parts water and then add some soil. The acid reacts with the shell fragments to release the gas carbon dioxide, so, if the water fizzes it is calcareous.

Once you have established your soil type and ascertained what the drainage is like, you will be well on your way to knowing which plants will thrive and which simply won’t. It is far easier to grow plants suitable to the soil in your region than to try to amend the soil. Once your garden is more established, you can always add a few potted plants or raised beds to grow some of your favourite exotic plants in.

Kirstenbosch Botanical Gardens. Picture courtesy Thomas Guillem. Visit his flickr pageKirstenbosch Botanical Gardens. Picture courtesy Thomas Guillem. Visit his flickr pageThe selection of plants available to grow on calcareous soils is far less than those adaptable to acidic soils, so when selecting the right plants for your Cape garden it is most important that you consult with your local garden centre. They know what does well in your area, so do not hesitate to ask them for advice.

If you are totally new to gardening in the Cape, friendly neighbours can give invaluable advice, or you many even decide to take a stroll through your suburb or local parks to take small cuttings of plants which appeal to you. These can be identified by your local horticulturalist. Even if you live on a small plot, planting a garden will help to stabilise soil, prevent dust and sand blowing into your house, create shade to cool the house and provide a space for animals and plants to live – creating an ecosystem and supporting biodiversity.

Indigenous plants are the best choice for your main framework of trees and shrubs because they have evolved over eons to adapt to their local environment. Indigenous plants have also developed a symbiotic relationship with many of the insects, birds and local animals over a long time, creating a complex system of life that we must support, rather than disrupt, in order to sustain the huge variety of life forms in the eco-system. In addition, local plants are adapted to the soil types and precipitation where they occur naturally and will require little supplementary watering – reducing the amount of water you need to keep your garden beautiful.

Kirstenbosch Botanical Gardens. Picture courtesy Thomas Guillem. Visit his flickr page.Kirstenbosch Botanical Gardens. Picture courtesy Thomas Guillem. Visit his flickr page.Remember, when planting indigenous plants it is most important that you chose plants that grow wild in your immediate vicinity, because plants from even a small distance away may cross-pollinate with other related wild species to form hybrids, and this may undermine conservation efforts. Be extremely careful not to plant any invasive alien species in your garden. Invasive alien species such as Rooikrans and Fountain Grass pose some of the greatest threats to biodiversity and also increase the risk of severe wild fires.

Because different localities in the Cape present a variety of growing conditions, including rainfall, wind exposure and soil type, one plant list will not suit everyone. Compiling lists for each region separately is also most exhaustive, so for now, I have compiled general plant lists which will help you with your selection, but which will still require some homework on your part to hone your list down to only those plants which are perfect for your area.