Cracking the Colour Code
Every spring South Africa’s arid west is transformed into a landscape of dazzling colour. Allan Ellis and Marinus De Jager explain what happens.
Why do these plants all flower at once?
The short answer is that they don’t. The longer answer is that although most do flower during spring, every species has a slightly different seasonal flowering pattern. Namaqualand is a desert and plant growth is largely confined to the winter rainy season. By spring, plants have accumulated enough reserves to splash out on producing flowers, which is an expensive business. It’s also warm enough for the essential pollinating insects to be active.
Annual plants, which are largely responsible for the swathes of colour in Namaqualand, grow every year from seed and live long enough to flower and set seed once only. They are therefore much more dependant on the short rainy season and are programmed to flower during spring, before the dry summer returns. Species that disobey the spring-flowering rule, such as Brunsvigias (Maartlelies) and Argyrodermas (Bababoudjies), will likely have large underground bulbs or fat succulent leaves in which to store the reserves they need for flowering, and so are less tied to the seasonal cycle.
Why are some flower patches multi-coloured and others dominated by orange or yellow?
The iconic, uniformly coloured flower patches of Namaqualand in spring are invariably found on disturbed areas such as old agricultural land, mined areas or heavily overgrazed veld. Opportunistic species that can handle these conditions are the typical Namaqua daisies Dimorphotheca sinuata, Ursinia cakilefolia and Osteospermum pinnatum.
The real treasures are in the less disturbed areas, which support a diverse multi-coloured display of perennial shrubs, annuals, succulents and bulbs. These species vary in their nutrient, water, sunlight and pollinator requirements, so each has a species niche and they avoid direct competition. Since the various insect pollinators often differ in their preferences or ability to perceive certain colours, flowering plants have responded by producing a multitude of floral colours, each suited to their own specific pollinators.
Do most of the flowers close at night?
Anyone who has been to Namaqualand will know it really isn’t worth flower spotting early in the morning, because the vast majority of flowers are still tightly shut. Flowers open only when temperatures are higher than a specific threshold, which varies between species and areas. This is a unique, intriguing aspect of Namaqualand’s floral displays and we don’t really know why most of the plants do it.
One idea is that closing at night and during cold fronts protects their pollen from moisture, which can damage it. Another is that closed flowers are less visible and thus less likely to become a meal for a hungry herbivore during the morning hours. Many pollinating insects also use closed flowers as bedrooms and may pay for their beds by delivering a pollination service when checking in or out.
Why do beetle-daisies have such prominent black spots on their petals?
The spots do look a little bit like the monkey-beetles commonly seen feeding in Namaqualand flowers, which is why early botanists named Gorteria diffusa the beetle-daisy. But this is a misnomer, because the spots are in fact mimicking a small black fly that is Gorteria’s main pollinator. Across Namaqualand Gorteria occurs in many different floral forms, some of which have elaborate spots so effective at mimicking female flies the male flies can’t resist. In the process of attempting to mate with the spots they pick up pollen that they then deliver to the next spotted Gorteria they visit in the hope its spots might be a true female.
Why do the hot-pink flowers in the Kamiesberg have such long floral tubes?
If you sit patiently watching a patch of bright pink Laperousia silenoides or Pelargonium incrassatum you might be lucky enough to see one of Namaqualand’s most spectacular animals, the long-tongued fly. They’re about 10 times bigger than a house fly and have ridiculously long mouthparts, up to 10 cm long. They insert their mouthparts into the long tubes of flowers to drink nectar and in the process get dusted with pollen, which they then transfer to another flower. Their long tongues can’t fold, so inserting them into the narrow flower tubes whilst in flight can be quite tricky. The flowers have evolved characteristic guidemarks to assist the flies in getting their aim right. There are a few species of long-tongued flies in Namaqualand and each visit a group of plant species with a different colour, so look out for white, cream, purple and pink flowers with long floral tubes.
What are the long protruberances at the back of dark purple Diascia flowers?
Unlike the long tubes of the long-tongued fly flowers, the twin spurs of Diascia namaquensis (bokhorinkies) don’t produce sugary nectar. Instead they produce oil which is collected by Rediviva bees who use it to feed their brood. When these bees insert their long, thin front legs into the Diascia spurs to scrape out the oil, the flower deposits a load of pollen onto their thorax. All Diascia flowers produce oil, but many of them don’t have long spurs. This is because there are several species of oil-collecting Rediviva bees, all with different leg lengths which match the spur lengths of their favourite oil plants.
See it for yourself:
To see beautiful spring blooms, visit one of these parks between July and September: Namaqua National Park, including the Skilpad Wildflower reserve; Richtersveld Transfrontier Park; West Coast National Park, especially the Postberg section; and Tankwa Karoo National Park. For more information go to www.sanparks.org.
Gurus: Dr Allan Ellis and PhD student Marinus de Jager are at the Botany and Zoology Department of Stellenbosch University. They study the evolution and ecology of Cape plants and insects.
Namaqua Beach Camp:
10% discount exclusive to Wild Card Members
The Flowers Beach Camp in the Namaqua National Park is open only during the flower season, offering a luxury stay amidst wildflowers on a pristine stretch of coast. At the Flowers Beach Camp you can enjoy elegant meals, coastal walks and 4x4 trips in splendid seclusion. All Wild Card members receive a 10% discount on bookings made. Open from 15 August to 16 September 2012. Click here to find out more.