Watsonia marginata (L. f.) Ker-Gawl.

Family: Iridaceae (Iris Family)
Common names:
Watsonia, Kanol, Kanolpypie

Watsonia marginata

Flowering spikeWatsonia marginata is a very pretty plant, with attractive foliage and gorgeous spikes of cup-shaped pink or white flowers. It is easily distinguished from other species of Watsonia by both by its leaves and its flowers. The leaves are made distinctive by being unusually broad, bluish-green in colour and with pronounced, heavily thickened, yellowish margins while the flowers are different from other members of this genus in that they are actinomorphic (radially symmetrical, as in a flower that can be divided into two identical halves (mirror images) along more than one plane), and they have a short and narrow perianth tube where other members are zygomorphic (of unequal or irregular shape, divisible into equal halves in one plane only) and have longer and wider perianth tubes. In other words, Watsonia marginata flowers are cup-shaped and Ixia-like compared to its tubular-flowered relatives.

LeavesThis watsonia is a deciduous, winter-growing, summer-dormant corm. Each corm produces 3 - 4 broadly sword-shaped, bluish-green leaves with pronounced yellowish margins and prominent midribs. The leaves appear in autumn, and stand one-third to two-thirds as high as the flower spike, i.e. 40 - 60 cm tall. Towards the end of their growing season, each corm sends up one straight, tall flower spike, each spike reaching a height of 1.2 - 1.5 m occasionally as high as 2 m. The spike has a large number of short branches which are closely pressed against the main axis of the flower stalk, each carrying a few flowers, with the whole spike carrying up to ±50 densely packed flowers. The flowering season extends for about 4 weeks during spring to early summer (Sept. to Nov.). Flower colour is variable, occurring in shades of mauve, pink or white, even maroon, and the centre of each flower is marked with magenta and white. There are also dwarf forms with pink or white flowers, where the flower spike is only about 0.5 m tall. At Kirstenbosch, although we have various shades of mauve, pink and white and dwarf forms in the collection, we display a mauve flowered form and the white form called 'Star Spike' in the Garden, both of which are tall. The pollinator is the honeybee. The fruit of Watsonia marginata is a small, rounded, woody capsule of several angular brownish seeds with prominent membranous ridges.

Watsonia marginata occurs in the winter-rainfall region of South Africa in the area between the Bokkeveld Mountains near Nieuwoudtville in the north to the Cape Peninsula and the Caledon district in the south, and is virtually restricted to areas of complete summer drought. It can be found growing from near sea level to middle elevations in the mountains, in stony clay soils and sometimes in seasonally marshy or temporary seep areas in sandy soils.

The genus Watsonia was named in 1752 by Philip Miller of the Chelsea Physic Garden after his friend Sir William Watson 1715-87, a physician and naturalist. The specific name marginata is Latin for marginate (having a margin) and alludes to the thickened leaf margins. Watsonia marginata was first collected in 1773 and described in 1782. The Afrikaans common name kanol is a phonetically corrupted version of the original Dutch work 'knol' meaning a corm, and is applied to many cormous species although mainly to species of Watsonia. It is often accompanied by a descriptive prefix e.g. rooikanol (red corm) if the flowers are red or suurkanol if the corm is sour tasting. The name is also often combined with pypie as in kanolpypie, pypie being the Afrikaans name for a miniature long-stemmed pipe which the tubular flowers resemble.

Watsonia marginata belongs in the Iridaceae (iris family), a family of roughly 70 genera and 1800 species which occur all over the world. Other members of this family well known to gardeners and florists alike include Iris, Gladiolus, Freesia and Dietes. The genus Watsonia is one of the larger genera in this family, yet occurs only in southern Africa. It contains 52 species, 34 of which are concentrated in the winter-rainfall region, in the Western Cape, Northern Cape and Eastern Cape, 21 in the summer-rainfall regions of KwaZulu-Natal, Mpumalanga, Swaziland and the Eastern Cape, and 1 species in Madagascar.

White form

Growing Watsonia marginata

Watsonia marginata is a tough, low maintenance, easy plant in cultivation. It is shown to best effect when mass planted, but also looks good when planted amongst other plants in the rockery, or mixed border where even when not in flower, its leaves provide interesting colour and texture. It is also a suitable subject for traffic islands or roadside planting in the winter-rainfall areas. Watsonia marginata will grow in containers, although the dwarf forms make better pot subjects, but it has a very vigorous root system and requires a large pot and must be repotted every year if it is to flower well.

This watsonia requires a full sun, or a position that gets sun for most of the day, and well-drained, compost enriched soil. It is tender to frost, hardy to a winter minimum of -1 oC / 30 oF (Zone 10) and in cold areas, requires a warm situation that is protected from the morning sun. In the summer rainfall regions, it must be planted in sandy well-drained soil or lifted every season, as the corms tend to rot if allowed to get wet during dormancy. Corms should be planted in autumn (March to April), whilst still dormant, at a depth of approximately twice their diameter (4-6 cm deep) and watered sparingly. After they have sprouted, they should be kept moist. They are not particularly sensitive to drying out, and it is best to err on the dry side that to over water, and particularly not to let them sit in water that cannot drain away. They do not need to be fertilised, but benefit greatly from the addition of generous quantities of well-rotted organic matter to the soil. If the soil is very poor, the plants can be fed with small amounts of high potash granular or liquid organic fertiliser during the growing season, but overfeeding will encourage leaf growth and reduce the number of flowers. It is not necessary to lift the corms every year, but it can be done if required i.e. flowering will not be detrimentally affected if they are lifted every year, and it should be done if the bed they are planted in is going to be irrigated during summer. It is necessary to lift and divide the corms every three to five years, otherwise the plants become overcrowded and flowering decreases. Once the plants are completely dormant (in November-December) the leaves can be removed at ground level or the corms can be lifted and stored in a cool dry place. If they are left in the garden, they should be kept as dry as possible.

Propagation is by seed or division of offsets.
Seed is sown in autumn, from April until June, thinly, in deep (min. 10 cm) seed trays, to allow for root development. The soil medium should be well-drained, a recommended mix being 2 parts sand : 2 parts compost : 1 part loam or equal parts sand and compost, and the seeds should be planted 3 - 4 mm deep, covered with clean sand and kept moist and lightly shaded. It is also advisable to protect them from rain during this period. Seed germinates readily within 3 to 4 weeks. Watering should be reduced towards the end of the growing season and withheld completely when they are dormant. The young corms should be lifted at the end of their first season and stored in dry peat in a cool, dry place to prevent rotting, then replanted in March at a depth of one-and-a-half times their size, and spaced 3 cm apart in order to allow sufficient space for the development of the corms. The young plants should flower in their third season.
Although Watsonia marginata does produce offsets (daughter bulbs) it does not produce them as abundantly as other species of Watsonia. When the corms are being lifted for replanting every 3 to 5 years, the corm clusters can be broken apart and replanted. This should be done during the dormant period (December to April) with replanting done in autumn (March to April).

Watsonia is grown as a garden plant in many countries, but it must be noted that it is a declared invasive weed in Australia. Gardeners that are concerned about growing potentially invasive species should contact their local conservation authority for advice or a list of species to avoid.

· Du Plessis, N., & Duncan, G., 1989, Bulbous Plants of Southern Africa, A guide to their Cultivation and Propagation, Tafelberg, Cape Town
· Duncan, Graham, personal communication
· Goldblatt, P., 1989, The Genus Watsonia, National Botanic Gardens, Cape Town.
· Jackson, W.P.U., 1990, Origins and Meanings of Names of South African Plant Genera, U.C.T. Printing Dept., Cape Town.
· Smith, C.A., 1699, Common Names of South African Plants, Dept. of Agricultural Technical Services, Botanical Survey Memoir No 35, Government Printer.
· Leistner, O.A. (ed.), 2000, Seed plants of southern Africa: families and genera, Strelitzia 10., National Botanical Institute, Pretoria.

Alice Notten
Kirstenbosch NBG
October 2001

To find out if SANBI has seed of this or other SA species, please email our seedroom.

This page forms part of the South African National Biodiversity Institute's plant information website www.plantzafrica.com.