Two general bands around the earth's surface, known as the temperate zones, lie between 30 and 50 latitude north and south. The climate in these bands is the most suitable for grape production. A Mediterranean climate of cool, rainy winters and warm, sunny summers is the most favorable for the wine vine. The southwestern area of South Africa, around Cape Town, is fortunate to have this Mediterranean climate and the soil composition to make great wines.
The moderate Mediterranean climate of the Cape is temperate with southeasterly Antarctic winds cooling the effect of the summer sun. A winter northwesterly wind brings bouts of rain and moderately cool temperatures. Occasionally, the peaks of the highest mountains in the winelands are dusted with snow. As a broad generalization, temperatures range from 55° - 75° in the summer months and 45° - 55° in the winter. Paarl is often 5° warmer than Stellenbosch, which is warmer than Walker Bay. Where the northwesterly winds bring rain, the southeaster blows it away. Both the summer and winter winds are often gale force, blowing between 25 - 60 miles per hour. January to June is usually calm, with gentle breezes and little rainfall. Harvest is February through April.
Although the wine growing regions cover a vast expanse of the Western Cape, the premium estate wine is grown mostly within a ninety minute drive of the city of Cape Town. In this southwestern tip of the country (red semi-circle on topographic map below), the mountains interupt the wind flow capturing the winter rain / summer winds weather pattern that is ideal for wine vines. The land north of the mountains is savanna and to the east, tropical.
The first land formed some 600 million years ago when the Paarl Mountain intruded their massive granite domes into the marine sediment. The Paarl Rocks are the second largest granite outcrop in the world, measuring some 654 meters (the largest outcrop is Ayers Rock in Australia).
Table Mountain with its symmetric pose over Cape Town and its expansive body and tail to Cape Point, formed its imposing position some 400 million years ago. This was a time of great activity as the impressive mountains around Stellenbosch and Franschhoek also date from this time. The rock formations of the Table Mountain era is that of younger sandstone resting on a floor of slate and granite.
The age, composition and relative stability of the Table Mountain structure created a unique environment for flora and fauna. There are more unique species of plant life on Table Mountain than any other ecological site. On the top of Table Mountain alone, there are more than five times the number of unique floral species than have been catalogued in the entire state of California.
Three basic parent materials produce the following soil types:
These soil types can be loosely grouped into five categories:
Structureless soils indicate that there are no restrictive layers in the sub-soil, which would impede growth. Several types of structureless soils have been identified at the Cape, but the most important ones for the vine are Hutton and Clovelly as well as Fernwood.
Hutton and Clovelly are well-drained soils of red and yellow color respectively. They generally require little preparation and tend to have a high clay content with compaction in the sub-soil.
Fernwood is represented by dry, sandy soils. This soil type tends to water drainage and consequent loss of nutritional value. Farmers generally use regular, light irrigation to keep the soil moist and cover it with organic mulch material.
Duplex soils feature a noticeable difference between the topsoil and that of the sub-soil. The main examples of Duplex soils include Kroonstad, Sterkspruit and Estcourt soil forms. These make up a very large portion of the soils in the western Cape coastal region. They have relatively sandy top-soil and an underlying clay pan.
Structured soils are represented by the Swartland and Valsrivier forms. They are derived from shale and have a dense, clay-ey sub-soil with underlying fragmented shale, which usually has a high salt content.
Shallow soils feature a layer of top-soil directly over rock. These soils are known as Mispah or Glenrosa, depending on the state of disintegration.
Deposited by the rivers over the ages, it is made up of alternating layers of soils of different textures. These layered alluvial soils are known as the Dundee form. The Eerste, Olifants, Berg and Breede rivers are the main sites of the Cape Winelands for this alluvial type of soil.