For the identification of insects and other fauna and flora of South Africa.

Monday, October 15, 2012

White or common arum lily (Zantedeschia aethiopica)

Family Araceae
I remember years ago the Arum Lily came in only one color ..... white ... and we called them 'funeral flowers'. Now there are many hybrids and a wonderful addition to a garden.

Also called a Calla Lily


It is an excellent cutflower and lasts a long time in water. Nowadays there are other forms of this species which will enliven an old theme. The 'Marshmallow' with a creamy pink spathe (outer "petal" which is actually a modified leaf) and rose-pink throat and the 'Green Goddess'with a green and white spathe. There is also an attractive form with leaves spotted white.

This lovely plant was introduced to Europe very early on, apparently before Van Riebeeck had established the refreshment station at the Cape. It is also illustrated in an account of the Royal Garden in Paris in 1664. It was sent as one of the interesting plants of the Cape to Europe by Simon van der Stel some time before 1697.


The striking arum lily "flower" is actually many tiny flowers arranged in a complex spiral pattern on the central column (spadix). The tiny flowers are arranged in male and female zones on the spadix. The top 7 cm are male flowers and the lower 1.8 cm are female. If you look through a hand-lens you may see the stringy pollen emerging from the male flowers which consist largely of anthers. The female flowers have an ovary with a short stalk above it, which is the style (where the pollen is received). The spadix is surrounded by the white or coloured spathe. According to Marloth, the whiteness of the spathe is not caused by pigmentation, but is an optical effect produced by numerous airspaces beneath the epidermis.


The flowers are faintly scented and this attracts various crawling insects and bees which are responsible for pollinating the flowers. Cross pollination occurs as the anthers of each flower ripen before the ovaries. A white crab spider of the family Thomisidae visits the flower to eat the insects. This spider does not spin webs and uses its whiteness as camouflage against the spathe. In the western Cape, a tiny frog Hyperolius hopstocki is also attacted to the arum lily flowers. The spathe turns green after flowering and covers the ripening berries. It rots away when these are ripe and the succulent yellow berries attract birds, which are responsible for seed dispersal.