Thamnochortus spicigerus (Thunb.) Spreng.
Common names: large thatching reed (Engl.); duineriet, olifantsriet, dekriet (Afr.)
Thamnochortus spicigerus is a striking, tufted- or tussock-forming perennial that will make a lovely feature in your garden. The dark brown spikelets will add an excellent contrast to your garden. Female and male plants are separate and look very similar when they are young.
Thamnochortus spicigerus is a giant, wide, unbranched restio, up to 2 m in height, with a base and crown diameter of 1–4 m, with well-developed rhizomes. The culms (stems) are unbranched, stout, and often with a slight curve, 5–20 mm apart, with a diameter of 4–8 mm.
The male inflorescence is similar to the female inflorescence, often more than 100 mm in length, with many spikelets and small spathe, 17–30 mm long. The male spikelet is pendulous (erect when young), dark brown with many flowers. Female spikelets are stiffly erect, egg-shaped, dark brown and with many flowers. Bracts for male and female are papery and much longer than the flowers.
Small brown flowers appear within the inflorescencein winter, from June to August.
Fruit is a nutlet, shed with the perianth attached; the winged sepals aid in wind dispersal of the fruit. The brown winged seeds, ± 1.77 mm in diameter, are released in early summer (November).
This species is Red Listed as Least Concern (LC); it is widespread and appears not to be threatened in the wild.
Distribution and habitat
Thamnochortus spicigerus is found on deep sand of the West Coast and on the Cape Flats north of False Bay, 1–130 m above sea level. Its distribution covers an area from Langebaan, Malmesbury to Cape Point. It is typically a strandveld species, and is common on sand flats. Growing conditions include well-drained, alkaline coastal sand, with most rain falling in winter.
Derivation of name and historical aspects
The Restionaceae family contains about 28 genera and 400 species. Members of the Restionaceae family are largely confined to the southern hemisphere. There are about 33 species of Thamnochortus with most of them occurring in the Cape Floristic Region, and a few in the Eastern Cape. Restionaceae comes from Latin word, restis, meaning ‘a rope’ or ‘cord’, alluding to the use of the plant.
The genus Thamnochortus originates from the Greek words, thamno, meaning ‘bush’, and chortus meaning ‘green herbage’. The Latin word spicigerus means ‘bearing flower spikes’, a reference to their large inflorescences.
Thamnochortus spicigerus is adapted to be pollinated by wind, like most members of the Restionaceae. The male inflorescences sway in the wind, releasing pollen, whereas, the female flowers catch the pollen from the air in their bracts, and funnel it towards the styles. Large amount of small, winged seeds are produced in October–November (early summer); many seeds that are produced are not viable. Once ripe, the bracts open and the seeds readily fall out, and are dispersed by wind.
The duine riet has adapted to survive fires in the wild by dispersing their seeds; the seed is stored in the upper layer of the soil and after fire and smoke, seeds germinate as the smoke break down the seed dormancy. Thamnochortus spicigerus is a resprouter and will send up shoots from the base of the plant (rhizomes) after fire.
Thamnochortus spicigerus is used as an excellent thatching material. The duine riet has a good horticultural potential as a landscape plant for low maintenance gardens. Flowers are used as cut flowers and they are long lasting.
Growing Thamnochortus spicigerus
Propagate Thamnochortus spicigerus by seed or vegetatively by division. Plants grown from division will take up to a year to grow, and do not look as vigorous as plants raised from seed.
Sow seeds in autumn, when the days are still warm, between 20–25°C and the nights are cool, between 8–10°C. Seeds require smoke treatment in a smoke tent for 30 minutes or soaked in a smoke water solution before sowing, in order to enhance their germination. Sow seeds into a seed tray using a sowing medium consisting of 1 part bark and 2 parts sand; firm down and cover with a layer of milled bark and water lightly. Keep the trays damp, and place them in a warm light area. Germination could be erratic but should begin after three to four weeks, and after six to eight weeks seedlings can be pricked out into 6 packs or larger containers using a well-drained fynbos mix.
Divide Thamnochortus spicigerus just before the crop of the new shoot emerges from the ground, in early or midwinter, from May to August. The plant should be divided into fairly large pieces. Care should be taken for the roots not to be disturbed, and plant out immediately in the ground or in containers. Keep the plant well watered after transplanting, until the new shoots are growing. Plants will take up to a year to grow and be ready for planting in the garden.
Thamnochortus spicigerus is best suited to fynbos gardens that have a well-drained soil, and grows in deep sand on the coastal foreland in the wild. The plant should be planted in a sunny position with good air circulation. Do not plant very close to a wall.
Before planting apply well-rotted compost to the soil. The best time to plant in the garden is at the beginning of the rainy season (May to August), so that the plants can be established before the dry, hot, windy summer arrives or water regularly during the first three months after planting. Once they are growing well, they need very little water. Plant in groups of four or more with other fynbos plants, to create a spectacular display. Good companion plants will include Erica multumbellifera, Protea burchellii, Helichrysum cymosum and Geranium incanum.
Thamnochortus spicigerus is relatively free from pests and diseases in the garden. It is subject to damping off as seedlings, if it is over watered, or if there is little or no air movement.
- Brown, N., Jamieson, H. & Botha, P. 1998. Grow restios. Kirstenbosch Gardening Series. National Botanical Institute, Cape Town.
- Daydon Jackson, B. 1928. A glossary of botanic terms Edition 4. Gerald Duckworth, London.
- Haaksma, E.D. & Linder, H.P. 2000. Restios of the Fynbos. Botanical Society of South Africa, Cape Town.
- Raimondo, D. et al. 2009. Red list of South African plants. Strelitzia 25. SANBI (South African National Biodiversity Institute), Pretoria.
- Smith, C.A 1966. Common names of South African plants. Memoirs of the Botanical Survey of South Africa No. 35.
Kirstenbosch National Botanical Garden
Plant Type: Restio
SA Distribution: Western Cape
Soil type: Sandy
Flowering season: Spring
PH: Alkaline, Neutral
Flower colour: Brown
Aspect: Full Sun
Gardening skill: Average