Desmodium uncinatum (Jacq.) DC.
Hedysarum uncinatum Jacq. [basionym]
Meibomia uncinata (Jacq.) Kuntze
Family: Fabaceae (alt. Leguminosae) subfamily: Faboideae tribe: Desmodieae subtribe: Desmodiinae. Also placed in: Papilionaceae.
silverleaf desmodium; Spanish tick-clover (English); spanischer Klee (German); desmodio plateado (Spanish); pega pega (Spanish).
D. uncinatum is a large perennial legume with stems that may grow several metres long and trail over surrounding vegetation. These cylindrical or angular stems are covered with short, hooked hairs that stick to hair or clothing. The stems can root at the nodes if they touch moist soil. The trifoliate leaves have pointed leaflets (up to 10 cm long x 5 cm wide); the upper side is dark green with an irregular generally pyriform silvering about the midrib, the lower side lighter green and uniform in colour, both covered with whitish hairs. Flowering stems may be up to 1 m high ending in fairly open racemes on a long peduncle with paired pink to bluish flowers; curved pods may break into up to 8 segments when mature. Pod segments are covered with short hooked hairs that stick to animals and clothing. Seeds mainly light brown with mixture of olive-green to cream, 200,000–220,000/kg.
South America: Argentina (subtropical), Bolivia, Brazil, Paraguay, Peru, Uruguay, Venezuela (west).
Now locally naturalised elsewhere in the highland tropics and humid subtropics.
Sown in permanent grazing pastures but also used for cut-and-carry, for green or conserved feed, for ground cover and in cropping for intercropping and mulch. Abundant leaf fall and runner decay provide a deep duff layer under the plants.
Generally grows best on lighter and more friable soils of moderate fertility, but not on heavy clays. ‘Silverleaf’ is more tolerant of low pH , high Al and Mn than ‘Greenleaf’ (D. intortum ) but cannot stand salinity. More tolerant of poor drainage and high water tables than ‘Greenleaf’.
‘Silverleaf’ needs rainfall exceeding 1,000 mm with good distribution throughout the year. Although not productive during the dry season, it will persist in regions with dry seasons of 3 months. With its stronger taproot , D. uncinatum proved decidedly more drought -tolerant than D. intortum in Zimbabwe. It will grow in wet soils and tolerate short term flooding.
It is a warm season plant but with good tolerance of cooler conditions. Peaks of growth occur in spring and autumn with a slight depression in the heat of mid-summer. Generally grown at moderate altitudes (to 2,000 m) in the tropics and lower altitudes in the subtropics. It is one of the most cool-tolerant tropical legumes although leaves are damaged or killed by frost.
It is moderately tolerant of shaded conditions.
‘Silverleaf’ requires fairly lenient grazing; it regresses to a small plant or dies out under constant heavy defoliation below 10 cm. ‘Silverleaf’ pastures tend to decline even under good management.
Pastures containing D. uncinatum are not normally burned, but the plants can recover after a fire.
Guidelines for the establishment and management of sown pastures.
D. uncinatum is usually planted from seed into a well-prepared seed bed, but has been sod-seeded into herbicide-treated pasture. Seed should be inoculated with specific ‘Desmodium’ group rhizobium (CB 627 in Australia), and Mo may be beneficial. Seedling establishment is initially slow, but the established legume starts to grow soon after the cool season.
High levels of fertility are needed for satisfactory growth and P, S, K may need to be applied before planting and as maintenance.
Compatibility (with other species)
‘Silverleaf’ is usually grown with grasses that are also cold-tolerant, for example Setaria, although it can combine with other tussock species. It has be grown with creeping grasses but does not persist under heavy grazing.
Pests and diseases
‘Silverleaf’ in Australia suffers from the root-chewing larvae of the weevils Amenmus quadrituberculatus and Leptopius spp. Mycoplasma-like organisms can develop ‘little-leaf’ symptoms on individual plants but this is not important in a pasture .
Ability to spread
Seed pod segments of D. uncinatum adhering to animal coats can facilitate spread. The legume can also spread through its trailing stems that root in moist soils at the nodes; however, it will only spread into suitably fertile soils.
D. uncinatum can spread into forest margins trailing over shrubs but does not climb into trees.
Nutritional value is high although tannin levels can exceed 3%. This can act as ‘by-pass’ protein increasing the efficiency of digestion, but also slows nitrogen cycling from leaf drop.
The high tannin levels reduce palatability until stock acquire the taste for it.
No toxicity has been recorded.
Legume yields of 4–7 t/ha and legume/grass yields of 15 t/ha DM have been recorded, with increases of 90–150 kg/ha in soil nitrogen.
Self-fertile; diploid . Will cross with D. intortum .
Flowering occurs in response to short days in mid-April when vegetative growth ceases. Selfing of the flowers can take place, but cross-pollination is important for satisfactory seed set. Seed matures about mid-June when the branches die back. The seed crop is mowed when 50 percent of the seed is ripe, allowed to dry in a swath for 10–14 days before threshing for seed yields of 330 kg/ha. In Queensland, commercial yields are 220–275 kg/ha using direct heading in the field. Slow drum speed (200 rpm) reduced seed cracking.
Some tolerance to 2,4-D.
- For cooler regions.
- Long growing season .
- Poor persistence especially under heavy grazing.
- Needs fertile soils.
- Hacker, J.B. (1992) Desmodium uncinatum (Jacq.) DC. In: 't Mannetje, L. and Jones, R.M. (eds) Plant Resources of South-East Asia No. 4. Forages. pp. 116–118. (Pudoc Scientific Publishers, Wageningen, the Netherlands).
- Sweeney, F.C. and Hopkinson, J.M. (1975) Vegetative growth of nineteen tropical and sub-tropical pasture grasses and legumes in relation to temperature . Tropical Grasslands, 9, 209-217.
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