The Western Cape: winter rain, dry summers and what to plant when

Frost and rain

The south-western corner of South Africa has a Mediterranean climate. SANBI describes a long, hot, dry summer from November to March and a short, cool, rainy winter from June to August, and the gardener’s year is built on that. The cool, wet months are the growing season, planting goes in from autumn to spring, and the summer is for keeping alive what is already in the ground. The wind is part of the climate too: it is strong on the coast and relentless in the dry months.

Frost

No first or last frost date is published for this zone. SANBI classes the coastal winter rainfall belt as virtually frost free, with a mean minimum of 0 to 10 °C in the coldest month. It says that when frost does occur there it is very light and short lived. The winter rainfall Karoo is a step colder, with light frost, though the northern and coastal parts of Namaqualand have little or none. At Kirstenbosch the coldest nights dip to about 7 °C, while at SANBI’s garden at Worcester, inland, the sunrise lows in winter are around 2 °C and fall to -2 °C in July and August.

That makes the coast a gentle place for tender plants, and the inland valleys a colder one. A clear, still night after a cold front is the dangerous one, and cold air drains into the lowest ground. In an inland garden, cover clivia, citrus and young plumbago before dusk and keep them against a warm wall. Winter winds are strong at Worcester, so shelter matters as well as warmth.

Rain and watering

More than half of Kirstenbosch’s average 1,310 mm falls in winter, with about 14 rainy days in each winter month. June, July and August each bring roughly 200 to 250 mm, while December, January and February bring only 24 to 33 mm, on four or five rainy days. SANBI’s Karoo Desert garden at Worcester gets very little or no rain in summer, and its winter rain is unpredictable. On the Bokkeveld plateau the rain falls in winter and spring.

From December to March, then, every drop is carried. Soak deeply once or twice a week rather than sprinkling daily, water at dawn and mulch heavily. Shade young plants, and group pots together. Established fynbos lives on winter rain, as the king protea does, and resents summer water. In the cool, wet winter the risk turns to rot, so plant in raised or free-draining ground. Indoors, the wet cold months slow growth and the compost dries slowly, so water houseplants sparingly. See holiday watering for the summer break.

Month by month

Each month below adds the local timing to the matching southern hemisphere page, which has the general list.

January

Dry, hot and windy, and the job is keeping alive what you planted in spring. Sow beans, beetroot, carrots, lettuce, radish and Swiss chard for autumn, into a drill watered the night before and shaded with a board for the first week. Water at dawn and mulch. The general list is on January, south of the equator.

February

The driest and hardest month, with the soil as dust. Sow the autumn crops into a watered drill under shade, divide agapanthus after it flowers, and order the bulbs before the good ones sell. The general list is on February, south of the equator.

March

The first rains are not far off, and this is the best planting month of the year. Plant daffodils, hyacinths and garlic, and plant fynbos so that it is established before next summer. Sow protea seed from the middle of the month, when the days begin to cool, covered with about a centimetre of sand. The general list is on March, south of the equator.

April

The first storms arrive and the fynbos recovers. Sow peas, onions, lettuce, spinach, kale, beetroot and carrots, plant garlic, and sow sweet peas and pot marigolds. Plant seedlings of the winter annuals. The general list is on April, south of the equator.

May

The rain is now properly under way, so this is a busy planting month rather than a quiet one. Plant pre-chilled tulips, hardy perennials and evergreens, and sow peas and broad beans. Mulch the beds against the cold. The general list is on May, south of the equator.

June

Cold, wet and changeable, with many clear days between the storms. Plant liliums the day you buy them and put in the winter colour, such as Iceland poppies, pansies and calendula. Plant seedlings of broccoli, cabbage and cauliflower. The general list is on June, south of the equator.

July

The coolest and wettest month. Plant bare-root roses and deciduous fruit trees, and prune roses, fruit trees and vines. The danger is rot in cold, wet ground, so plant in free-draining soil. The general list is on July, south of the equator.

August

The rain is still falling and the soil is cold and moist. Sow seed in raised or well drained ground, and later in the month rather than earlier, and start tomatoes and peppers under cover. Fynbos is coming into flower. The general list is on August, south of the equator.

September

Spring, which SANBI calls the most colourful season at Kirstenbosch. Sow beans, cucumbers, carrots and courgettes, plant out tomatoes and potatoes, and plant the summer bulbs. Set up the watering before you need it. The general list is on September, south of the equator.

October

The rain tails off and the heat starts. Sow basil, pumpkin and sweet corn, plant out the summer vegetables, and begin deep watering twice a week with a thick mulch. The general list is on October, south of the equator.

November

Hot and drying out, with the spring annuals finished. Plant fast annuals and herbs, shade anything small for its first days, and plant in the evening. Do not start a new bed that you cannot water through the summer. The general list is on November, south of the equator.

December

Nothing falls for weeks, so every drop is carried. Mulch matters more here than anywhere in the country, and shade is not optional for young plants. Water the pots as well as the beds, and group them in the shade. The general list is on December, south of the equator.

Plants that belong here

• King protea comes from fynbos, wants acid, sandy, free-draining ground and no fertiliser, and is sown from March.
• Geranium comes from dry rocky places in the Cape and wants sun, sharp drainage and a dry spell between waterings.
• Agapanthus wants sun all day and deep weekly water in spring, then asks for very little once it is settled.
• Cape leadwort is a South African native that tolerates drought once it is established.
• Bird of paradise is the floral emblem of Cape Town and wants full sun, so plant it where the winter rain drains away rather than collects.
• Trailing ice plant is a South African succulent daisy that wants the hottest, driest, meanest spot you have.
• Lavender is a Mediterranean shrub that wants sun, poor soil and sharp drainage, which a Cape summer gives it.
• Rosemary is a Mediterranean shrub that does better with less water, and a wall that holds the day’s heat.
• Sweet pea is sown in autumn here, grows through the cool weather and flowers before the heat returns.

See the South African plants shelf for more natives.

Questions from the margin

Read on

Planting almanac for this region

Opens the almanac with this region and its hemisphere already chosen.

South African plants

Plants native to South Africa, checked against the SANBI PlantZAfrica database.