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Saturday, September 8, 2012

Blue-bells (Trichodesma angustifolium)

Family Boraginaceae
Dainty pale blue flowers, turning pink with age, cover bushes of Trichodesma angustifolium subsp. angustifolium in springtime, especially after fire. These blue-bells with much smaller flowers than their well-known sister species, the chocolate-bells, T. physaloides, are delicate and attractive.


Description


Trichodesma angustifolium subsp. angustifolium is a perennial herb with annual stems from a woody rootstock. Rounded bushes up to 0.5 m high and 2.0 m in diameter and a roughly appressed indumentum (covering of hairs) characterize the species.


The leaves are narrowly linear, ± 20-50 x 3-6 mm. The inflorescences are borne terminally. The calyx of the flowers is winged, enlarging in fruit and the corolla is ± 9-15 mm long, the lobes triangular, long acuminate, often twisted, and deep blue. Flowering time: from October to May.


The fruit consists of 4 nutlets.
 Conservation status

Currently Trichodesma angustifolium subsp. angustifolium is not threatened. However, the grasslands are threatened by human impact and this may change its status in future.

Distribution and habitat

The genus is widespread in southern Africa and is represented in various vegetation types ranging from grassland and savanna to succulent shrubland, mainly in the Grassland and Savanna Biomes. All southern African species extend further north into Africa. Trichodesma angustifolium subsp. angustifolium is disjunct in its distribution in southern Africa and is found in Namibia, Botswana, South Africa (Northern Province, North-West, Gauteng, Free State, northern KwaZulu-Natal and Northern Cape) and Mozambique. Blue-bells grow on red, sandy loam and stony soils. This species is essentially found in the moist summer rainfall areas of southern Africa.
Derivation of name and historical aspects
The name Trichodesma is derived from the Greek words, thrix or trikhos (hair), and desme (band or bundle), alluding to the twisted hairs or awns that terminate the anthers. The species name is a reference to the relatively narrow leaves.

The genus Trichodesma is a member of the family Boraginaceae (forget-me-nots), comprising about 45 species from the tropical and subtropical regions of Africa, Asia and Australia. In southern Africa, five species and three subspecies are recognized. The related T. physaloides occurs in the same area as this species.

The related T. physaloides (Chocolate Bells) occurs in the same area as this species.
 T. angustifolium subsp. angustifolium is closely related to T. africanum from the drier western parts of southern Africa.


T. angustifolium subsp. argenteum differs from the typical subspecies in its silver-grey appearance due to a dense covering of hair and its distribution in northern Namibia.

Ecology

With sturdy, often very old, fire-resistant rootstocks and mass seed production after fire-stimulated flowering, this species is well adapted to survive unfavourable conditions. Most fire-stimulated plants do flower in the absence of fire, but not as profusely as they would after a fire. Plants reach a considerable age and large rootstocks may be more than a century old.

A prominent feature of the flower is the calyx, which is strongly enlarged in fruit. The plant sheds the nutlet(s) with the calyx and style attached. The entire floral structure is relatively light and serves as a dispersal unit. Blue-bells are subject to winter drought, regular natural fires and frost.
 Uses and cultural aspects

It is used medicinally by grinding the dried root into a fine powder and adding it to cold water for treating diarrhoea.

Growing Trichodesma angustifolium subsp. angustifolium

This plant is not in general cultivation, probably because it does not flower well unless subjected to fire (intense heat). It presents a challenge to the keen gardener to create a suitable environment for it.