08
My Summer
ENVIRONMENT
DECEMBER 2020
ARUM LILIES – PART OF A COMPLEX ECOSYSTEM By Dr Anina Lee
M
ost of us living in the Western Cape (or other parts of southern Africa) are very familiar with Zantedeschia aethiopica, the beautiful white arum lilies that grow in marshy places along streams and wetlands – and in most suburban gardens.
However, if you live in Western Australia, you would not be thrilled to see them, as they have been declared an invasive alien weed there. The plant is thought to be named after an Italian physician/ botanist called Giovanni Zantedeschi, and the word ‘aethiopica’ once referred to anything south of the known world in classical times. The origin of the Afrikaans name ‘varkoor’ (pig’s ear) is much more obvious. The arum lily is not a true arum (belonging to the genus Arum), nor a true lily (belonging to the genus Lilium). But it does belong to the family Araceae – hence the name arum. But we love them and will call them whatever we wish. The arum lily flower is not what it seems. The big white funnel-shaped ‘petal’ is actually not a petal, but a modified leaf called a ‘spathe’. The minute flowers are arranged in an intricate spiral pattern on the yellow finger-like spine inside the spathe, called a ‘spadix’. The flowers are arranged in such a way that the male flowers appear on the top section of the spadix, and the female flowers on the lower third. The spadix is at first creamywhite and matures to bright yellow.
If you are a frog enthusiast, you will never pass an arum lily without peering into the flower on the off-chance of spotting a little arum lily frog (Hyperolius horstockii) curled up inside. These tiny animals must be the cutest frogs on the planet – small, creamy-white with orange legs that are usually tucked up below the white body to make it very inconspicuous. What is it doing there? Apart from being well-camouflaged against predators, it also lies in wait for unsuspecting insects that come to gather pollen from the male flowers. A tiny white crab spider is another perfectly camouflaged frequent inhabitant of the arum. The crab spider does not spin a web, but is an ambush hunter, waiting unseen for a hapless insect (usually a bee) that comes in expectation of a pollen larder. It seems impossible that such a tiny spider can capture and kill a bee, almost twice its size, but it does. Arums are very much on the menu for the large green or brown hawk moth caterpillars, which can strip a plant of all its leaves in a matter of days. The arum lily is one of the host plants for Hippotion celerio, commonly known as the silver-striped hawk moth or grape vine hawk moth. This is an exceptionally handsome, neat-looking moth with a wingspan of 76 mm and longitudinal pale brown and olive-brown stripes along the body and wings. I’m always delighted to share my arums with these beautiful creatures – both caterpillars and adult moths are so welcome. And the arums will grow new leaves in double-quick time.
The arum lily is one of the host plants for Hippotion celerio, commonly known as the silver-striped hawk moth or grape vine hawk moth. PHOTO: BioLib.cz
A tiny crab spider manages to ambush a hapless bee, which is almost twice its size. PHOTO: Annemiek Schilder
The secret of growing a butterfly garden is to grow food for the butterfly babies – the caterpillar larvae. The caterpillars metamorphose into the butterflies and moths we love to see. Both caterpillars and moths provide a valuable protein food source for birds and bats, which will also be attracted to such a nature-friendly garden.
The green fruit capsules form at the base of the spadix (where the female flowers are positioned). The ageing spathe turns green and curls up to shield the fruit. As the fruit matures, the spathe dries to reveal succulent yellow berries which entice birds that then assist with seed dispersal.
Porcupines are especially partial to arum lily rhizomes, which are succulent and nutritious. We may feel aggrieved and devastated when we behold the havoc wreaked in the garden by the spiky rodents, but it’s all part of nature’s plan. The porcupine is not a tidy eater, and its chomping of the arum roots results in numerous bits and pieces that will soon grow into many more little arums. It’s another natural dispersal mechanism in nature.
Most of us probably think of arums in terms of decoration, without considering the complex ecosystem that exists within and around the lily.
So if you are a true lover of nature, allow nature to share in your garden – whether it be butterflies, bees, spiders, frogs or even porcupines.
An arum lily frog (Hyperolius horstockii) lies in wait for unsuspecting insects that come to gather pollen from the male flowers. PHOTO: zanature.wordpress
