Beat the heat
Use colour to give garden oomph, writes Alice Spenser-higgs
DID you know that ‘hot’ coloured flowers stand up to sun and heat far better than their pastel counterparts? Notice how marigolds, coreopsis, rudbeckia, gaillardia and helenium — all flowers in shades of yellow and orange — just keep on flowering and looking good through the heat of January and February.
Hot colours, however, need to be used with care. Although flowers in shades of red, orange and deep tones of yellow create a vivacious garden, too many warm colours mixed together can produce a sense of restlessness.
The way to overcome this is to make use of transition zones consisting of grey, bronze or gold foliage plants or airy flowers like gaura or daisies.
Alternatively, use fewer blocks of colour offset by green.
By making sure that neutral colours are present as part of your colour design it is easier to hide an error, because clashing or overbright colours won’t be too inyour-face.
Contrasting the hot colours with blue or mauve flowers, especially those with silvery foliage, also adds interest to the garden without heating it up.
One of the most pleasing and popular colour schemes is blue and mauve, with yellow or orange for contrast and with silvery or blue-grey foliage as a buffer.
One of the reasons for wanting to introduce hot colours into the garden is the availability of the new Dahlia pinnata Dahlietta, a compact bedding dahlia in a dazzling array of hot colours such as Apricot Sunrise, Cherry Sunrise, Patricia (stripy red and yellow), Rachel (tangerine orange) and Sunburst.
They grow in full sun or partial shade in fertile soil and will develop into attractive mounded plants with a garden height of 20cm and a width of 30cm.
Dahlias are heavy feeders and benefit from frequent light fertil- izing, ideally a weekly feed with a balanced liquid plant food. From now until the first frost use a high potassium food. Regular watering is also essential, especially in very hot conditions. Removing the dead flowers encourages them to flower more and produces a better shaped plant.
The Dahlietta also performs well in containers and even as an indoor potted plant. When the flowers are over, the plant can be put outside or planted out in the garden.
Up on the highveld dahlias can be left in the ground over winter and are not likely to rot. They should be cut down when the foliage becomes unattractive, and will shoot up again in the spring.
The mini petunias (Calibrachoa) also add sun-drenched colour to the garden. The trailing Can-can has dark green foliage, top-to-toe flower coverage and a long flowering season.
It partners well with other sunloving annuals, and the long trailing branches cascade over the sides of mixed containers and hanging baskets or spread over flower beds. They perk up after rain, tolerate heat and are very disease resistant. Calibrachoa Can-can are available in five colours; terracotta, mocha, orange, apricot and strawberry.
The clear yellow of Gaillardia Mesa doesn’t fade in the heat and it is a nice alternative to marigolds. This first-year flowering perennial is very drought tolerant once established. It grows 40 to 50cm high, does not flop over, and is an improved version of the traditional gaillardia, producing more flowers from spring to autumn on more upright, well-branched plants.
It performs equally well in the garden or in containers.
Tips for beating the heat
Watering. During the hot summer months it is perfectly acceptable to water in the evening. The foliage dries off quickly in the warm evening air so there is little chance of disease.
Late afternoon or early evening watering is also more effective because evaporation is minimal. It has been found that plants absorb water best in the evening and are more able to stand up to the heat stress the following day. Watering can also be done early in the morning.
Mulch. A 5cm to 10cm mulch of organic material — peanut shells, bark chips, pine needles, macadamia nutshells or crushed apricot pips — spread over the surface of beds keeps the roots cool, reduces transpiration and protects the soil life. Regularly renew the mulch.
Fertilizing. Don’t fertilize when it is very hot because the development of new growth puts additional stress on the plant. Wait until conditions are cooler before fertilizing. However, you can apply a plant tonic, such as kelp or worm tea, as a soil drench.
Zoning. Group plants with the same water requirements together. Drought-tolerant plants like coreopsis, gaillardia, rudbeckia, portulaca and vinca have lower water requirements than dahlias, marigolds and roses.
Pest control. Spray preventatively to keep away pests, such as aphids, white fly, beetles, and caterpillars that will undermine the health of the plant and destroy the leaf cover, which shades and cools the plant. Use organic insecticides like Ludwig’s Insect Spray or Margaret Roberts’s Organic Insecticide or Margaret Roberts’s Biological Caterpillar Insecticide.
The plants mentioned in this article are available from leading garden centres.