Arum Lily
Created | Updated Mar 17, 2013
White Arum Lily
Willem says: 'The Phyto-Philes are for plant lovers of every size and shape, colour and flavour. As with my Colours of Wildlife column, I'll be featuring one species per article, illustrated with sketches, paintings, and/or photos. Over time I hope to be showcasing the amazing diversity of weird and wonderful plants that occur in South Africa, while also from time to time looking at the flora of other countries. While featuring many spectacular species, I'll not be neglecting the smaller, more humble kinds that are nevertheless fascinating in their own right.'
In this edition of the Post I co-ordinate the Colours of Wildlife and the Phyto-Philes columns! In Colours of Wildlife I tell you about the Arum Lily Frog; and here I will tell you about Arum Lilies! I specifically feature the White Arum Lily, Zantedeschia aethiopica, also known as Calla Lily or Easter Lily. In Afrikaans we call this 'Varkore' or 'Pig's Ears' because of the shape of the flower. Actually what we think of as a flower is, in this species, a much more complex structure. The white thing on the outside is actually not part of the flower but a modified leaf called a spathe. It surrounds the central flower stalk called a spadix, which is conspicuously yellow. The spadix carries the actual flowers; the upper 7 cm/ 3” or so carries the male flowers, which release sticky, white strings of pollen, while the bottom 1.8 cm/1 and a quarter inch carries the female flowers. To prevent the male flowers from pollinating the female flowers below it on the same spadix, the male flowers mature before the female flowers do, so the pollen hopefully has time to get carried to other flowers so that an exchange of genes between different individuals can happen.
The genus name for this species, Zantedeschia, commemorates the Italian botanist Giovanni Zantedeschi, who lived from the late eighteenth to middle nineteenth centuries. The species name, aethiopica, means 'from the Ethiopic region'. This typically refers to the whole of sub-Saharan Africa rather than just the country of Ethiopia. The genus Zantedeschia has seven or eight recognized species and is in nature restricted to Southern Africa, the furthest northern occurrence being in Malawi. Most species are endemic to South Africa. They are all similar in appearance, with broad leaves varying from sword-shaped to heart- or arrowhead-shaped as in this one. Some have fine white or yellow spots on the leaves. Their flowers also are similar in shape but the spathes can be white, yellow or pinkish to purplish. Zantedeschias are very popular world-wide as garden and cut flowers. In some regions such as Australia they have escaped into the wild and have become problematic invasive weeds.
In South Africa this is the most widespread Zantedeschia. It occurs from the Western Cape Province right through the southern and eastern regions to the northeastern corner of the Limpopo Province. It is only absent from the dry, central semi-desert regions of the country. They grow luxuriantly in moist places such as the edges of rivers, lakes and ponds, or marshes. They grow from the coast to high altitudes inland, and grow in the open sun as well as in the shade of riverside trees. The leaves reach a height of 1 m/3 ft with broad, dark-green blades. They can survive in waterlogged soils because the leaves have small pores called stomata that can exude excess water in small droplets, a process called 'guttation'. Where there is warmth and moisture year-round they grow continuously, but where there are cold winters and periods of drought the leaves can die back and re-sprout from the subterranean tubers and rhizomes when conditions are favourable again. They flower mostly in summer but in areas with suitable conditions the flowers can be seen practically year-round. It is an enchanting experience to come across a large colony of these in the wild – a huge field of luxurious dark leaves and amidst them thousands of beautiful white spathes with the little yellow spadixes poking up in their centres.
These plants contribute great ecological value in their native habitats. Although the tubers are poisonous, containing calcium oxalate crystals, porcupines and wild pigs will dig them up and eat them. The flowers exude a delicate perfume to attract a variety of pollinating insects like beetles and bees. These must creep into the centre of the spathe to reach the flowers on the spadix. But they might face some hazards on the way! The first is a kind of spider called a crab spider. These spiders don't weave webs, but hunt by camouflaging themselves – most species being able to change their colour – and then pouncing on their unsuspecting prey. The one that frequents the arum lilies can turn itself white so as to be inconspicuous against the spathe. There is a kind of tiny frog that does the same thing, the Arum Lily Frog, Hyperolius horstocki, which I feature in this edition's Colours of Wildlife! The frog as well as the spider make use of the arum lilies not only to lure their prey to within striking range, but also as convenient places to hide from predators that might want to hunt them in turn.
Once arum lilies have been pollinated – since not all of them contain frogs or spiders to gobble up potential pollinators – the spathes turn green and shrivel up against the spadix. On the spadix the successfully pollinated female flowers will now enlarge and turn into plump, yellow berries. When they are ripe the spathe will drop off, revealing them to birds who will come and eat them, so distributing their seeds in their droppings.
But arum lilies also propagate vegetatively. A growing plant will keep producing offshoots from its base which grow into new leaves and new subterranean tubers. A single plant can thus spread to form a colony or, in the garden, fill an entire bed.
Like many other plants (and animals) I've featured so far, this species is inappropriately named. It is not a lily (genus Lilium) or at all closely related. It is a monocotyledonous plant (the plants having a single seed leaf, forming one of the two main divisions of flowering plants, the other being the dicotyledons having two seed leaves) like lilies but that's all. It belongs to the Arum family, the majority of which can be easily recognized in flower, having the same characteristic structure of the spathe surrounding the spadix. This is a huge family comprising over 3700 known species, most being found in the tropics. South Africa is strangely deficient in aroids, these being the main ones, but there is an abundance of them in the rainforests of Asia and especially South America. Some species reach temperate regions such as North America and Europe (skunk cabbage, 'Lords and Ladies', 'Jack-in-the-Pulpit'). They are often found in marshes. In the tropics, though, they often form part of the forest understory and many species are epiphytes (growing on trees). They include the plants with the some of the most massive unbranched inflorescences (the titan arum Amorphophallum titanum) as well as some of the smallest flowering plants and fruit, the duckweed Wolffia. The aroid Alocasia macrorrhiza also sports the largest undivided leaves of all plants, reaching 3 m/10 ft in length. A couple of species are food plants, like Taro, Colocasia esculenta, and Delicious Monster, Monstera deliciosa. Many species are grown as ornamentals, the ones from the undergrowth of tropical forests being excellent house plants. A few are aquatic and useful for aquaria. A number of species are fascinating for being plants that produce body heat! Rapidly metabolization of nutrients can raise temperatures in the flower to 45 degrees Celsius/113 degrees Fahrenheit, which appears to attract insects. Some species produce pungent odours for the same purpose. The heat also helps some species to survive tissue damage in cold regions, and in the titan arum might contribute to the extremely rapid growth of the inflorescence.
The White Arum Lily of South Africa is so conspicuous that it seems to have been collected and taken to Europe even before Jan van Riebeeck landed in 1652 to establish the refreshment station that became the Cape Colony. They have proved easy to grow in Europe, America and Australia and can survive outside even in areas where the winter temperature goes down to 20 degrees Celsius/4 degrees Fahrenheit below zero. The flowers are long-lasting when cut, the spathe and spadix both having a firm, spongy texture. Because of its white colour symbolizing purity it is often used in bridal bouquets. It has been used almost to the point of cliché in paintings, here in South Africa but also in the works of overseas artists like Diego Rivera and Georgia O'Keeffe who sometimes called them calla lilies. So I'm trying for a straightforward, not-too-cliché representation in my own painting.
There are a few other recorded uses of this species. Cooking can neutralize the poisons in the leaves and tubers, and they are eaten in some communities. The boiled leaves can also be used as a dressing for wounds or to combat headaches; boiled tubers are mixed with syrup as a gargle. The leaves are also said to be used for a dye to turn wool yellow.
As I've said these plants are easy to grow. They can be grown from seeds; first remove the pulp and let the seeds dry out, then plant them in rich, well draining soil, well-spaced out. Plants can also be multiplied by division of clumps and tubers. They enjoy constantly moist soil and temperate climates – not too hot in summer, not too cold in winter – although as I've said the tubers can survive cold winters by becoming dormant. Under good conditions they grow rapidly; they grow well in the shade but flower best in sunny spots. I suggest these be planted where they have plenty of room to spread.
