Common name: Burrflower

Burrflower is a timber and landscape tree native to a wide geographic area. Its natural range extends from the Himalayan foothills, south to Sri Lanka, and through Burma, Thailand, Malaysia, Vietnam and Indonesia, to Papua New Guinea.

It is fast-growing in its early years and may attain a height of up to 35 m (115 ft) in closely spaced forests, though it is more commonly 15 to 20 m (50 to 65 ft) tall. The trunk is usually straight, uniform, sometimes with a slight buttress in large trees and supports a wide-spreading, rounded or umbrella-shaped crown. The bark is grey and smooth on young trees becoming slightly cracked as the tree ages.

The leaves are oval, 15 to 30 cm (6 to 12 in) long, light glossy green, prominently veined above, lightly haired underneath and alternately arranged and grouped at the ends of the branches. They remain on the tree in areas where the dry season is short but detach and fall to conserve water where it is long or pronounced. 

The flowers are tiny, funnel-shaped, orange and tightly packed in a round, pom-pom-like flower-head 4 to 6 cm (1.6 to 2.4 in) in diameter. 

These are followed by compound fruit made up of numerous small fruit compressed together in a ball that retains the shape of the flower-head and are fleshy, with many small seed inside.

Use

Burrflower produces a lightweight wood averaging around 350 kilograms per cubic meter (22 lbs per cubic ft), with low natural resistance to decay and rot. This places it in the non-durable softwood class, making it unsuitable for outdoor use or heavy construction generally.

The sawn timber is used mainly in light construction, indoor joinery and for making furniture, cabinets, boxes and crates. Selected logs are sliced into thin sheets for decorative veneer and plywood. The small-diameter and misshapen logs are pulped for making paper and composite woods such as particleboard.

Burrflower trees are occasionally cultivated as ornamentals for their shapely form, glossy green foliage and showy flowers.

Climate

Grows naturally and achieves its best development in humid subtropical and tropical climates, generally areas with annual lows of 16 to 25°C, annual highs of 27 to 35°C, annual rainfall of 1500 to 5000 mm and a dry season of 5 months or less. 

Although also known to grow and flower in sub-humid areas with annual rainfall as low as 500 mm and a dry season of up to 8 months, the trees tend to be severely stunted.

Growing

New plants are usually started from seed, which remain viable for three to five months if stored under cold, dry, airtight conditions. The seed are extracted from ripe fruit that have turned yellow to orange.

The ripe fruit are left to soak in water for three to four days, then are drained and heaped under shade for about one week to allow them to ferment and soften. They are then mashed and sieved to extract the fine seed, which are first sown in trays and then transplanted to individual containers when the seedlings are large enough to handle. The seedlings need shade for the first three to four months before they are ready for planting out.

It performs best on nutrient-rich, free- to slow-draining clay, loam or sand soils of a moderately acid to mildly alkaline nature, generally with a pH of 5.0 to 7.5, and on sites with full sun exposure.

Problem features

The fruit are reportedly eaten by bats, which disperse the seed. Burrflower is listed as a weed in at least one reference publication and is reported to have naturalised in Australia and Puerto Rico. Still, there does not appear to be any record of it as a serious weed anywhere in the world.

Books

• Champion, H. G. & Seth, S. K. 1968, A revised survey of the forest types of India, Natraj Publishers, Dehradun, India

• Chudnoff, M. 1984, Tropical timbers of the world, Forest Service, U.S. Department of Agriculture (USDA), Washington, D.C.

• Dey, S.C. 1996, Fragrant flowers for homes and gardens, trade and industry, Abhinav Publications, New Delhi, India

• Francis, J. K. 1998, Tree species for planting in forest, rural, and urban areas of Puerto Rico, U.S. Department of Agriculture, Forest Service, International Institute of Tropical Forestry, Río Piedras, Puerto Rico

• Francis, J. K. and Liogier, H. A. 1991, Naturalized exotic tree species in Puerto Rico, General technical report SO-82, USDA Forest Service, Southern Forest Experiment Station, New Orleans

• Francis, J. K. et al. 2000, Silvics of Native and Exotic Trees of Puerto Rico and the Caribbean Islands, Technical Report IITF-15, USDA Forest Service, Rio Piedras, Puerto Rico

• Krishen, P. 2006, Trees of Delhi : a field guide, Dorling Kindersley Publishers, Delhi

• Liegel, L. H. 1987. A technical guide for forest nursery management in the Caribbean and Latin America, U.S. Dept. of Agriculture, Forest Service, Southern Forest Experiment Station, New Orleans

• Little, E. L. 1974, Trees of Puerto Rico and the Virgin Islands, Vol. 2, United States Department of Agriculture (USDA), Washington D.C.

• Luna, R. K 1996, Plantation trees, International Book Distributors, Dehradun, Uttarakhand

• Randall, R. P. 2002, A global compendium of weeds, R.G. and F.J. Richardson Press, Melbourne

• Randall, R. P. 2007, The introduced flora of Australia and its weed status, Cooperative Research Centre for Australian Weed Management, Glen Osmond, South Australia

• Reyes, G. 1992, Wood densities of tropical tree species, U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station, New Orleans, Louisiana

• Scheffer, T. C & Morrell, J. J. 1998, Natural durability of wood : a worldwide checklist of species, Forest Research Laboratory, Oregon State University, Corvallis, Oregon

• Webb, D. B. 1984, A Guide to species selection for tropical and sub-tropical plantations, 2nd ed., Unit of Tropical Silviculture, Commonwealth Forestry Institute, University of Oxford, Oxfordshire