Common name: Yokewood

Yokewood or French oak is a flowering and timber tree originating from the Caribbean, where it occurs in natural forests on the islands of Jamaica and Hispaniola.

A medium-sized tree, it may reach heights of up to 30 m (98 ft) in its natural habitat, though it is more commonly 10 to 20 m (33 to 66 ft) tall and grows at a slow to moderate rate, depending on the growing conditions. 

The trunk is usually straight, with a small buttress in large trees, and supports a moderately branched, rounded crown. The bark is pale grey to brown, with vertical furrows and narrow, roughened ridges. 

The leaves are oblong to lance-shaped, up to 13 cm (5 in) long, on top glossy green, underneath dull light green. They are semi-evergreen to deciduous, with leaf-fall in the dry season to minimise water loss, followed by new leaf growth at the transition from the dry to the rainy season.

The flowers are trumpet-shaped, white tinted pink or solid pink with a pale yellow throat. They bloom in showy clusters at the beginning of the rainy season, coinciding with new leaf growth. 

Fertilised flowers are followed by thin seed capsules up to 50 cm (1.6 ft) long that hang dangling on the tree for months before turning brown and splitting lengthwise to release their seed. The small, lightweight seed are papery and winged, making them easily dispersed by wind.

Use

It is occasionally cultivated as a flowering tree in gardens and landscapes in its native range, particularly in low rainfall areas, because of its good tolerance to drought conditions.

Yokewood trees produce medium-weight to heavy wood in the 600 to 800 kg per cubic meter range. It is easy to work and has moderate to high natural resistance to rot, decay and termites. This classes it as a durable hardwood, suitable for both indoor and outdoor construction.

Although considered only a minor timber in its native range, the heartwood resembles that of Oak (Quercus) from temperate climates, being light- to pink-brown with darker streaks. Well-formed logs are sawn into planks used for making furniture, cabinets and floorboards. Small diameter or misshapen logs are split to make roof shingles or, together with the branchwood, cut-up for firewood and charcoal.

Climate

Grows naturally in sub-humid to humid tropical lowland climates, generally in areas with annual lows of 18 to 25°C, annual highs of 27 to 35°C, annual rainfall of 600 to 2500 mm and a dry season of 2 to 6 months. However, it has its best development in areas with annual rainfall of 1400 mm or more.

Growing

New plants are usually started from seed, which can be stored for up to twelve months under cold, dry, airtight conditions. They germinate within one to two weeks of being sown, without any pre-treatment needed. Seedlings should be exposed to full or near full sun when around a month old and can be planted out when only four to five months old.

Performs best on well-drained clay, loam and sand soils of a moderately acid to alkaline nature, generally with a pH of 5.5 to 8.0, and on sites with full to partial sun exposure. It has good tolerance to limestone soils, wind, drought and seasonal flooding.

Problem features

Yokewood trees start to flower and produce seed at an early age, with reports of flowering and fruiting in seedlings that are less than twelve months old. The young and mature trees produce abundant, viable, small, winged seed that gets carried by wind over long distances.

It is listed as a weed in at least one reference publication. However, there does not appear to be any reference of it anywhere as a serious weed. It was assessed to be a low weed risk species for Hawaii by the Hawaii Pacific Weed Risk Assessment (HPWRA) project.

Books

• Adams, C. D. 1972, Flowering plants of Jamaica, University of the West Indies, Mona, Greater Kingston

• Barwick, M., et al. 2004, Tropical & subtropical trees : a worldwide encyclopaedic guide, Thames and Hudson, London

• Cassidy, F. G. & Le Page, R. B. 1980, Dictionary of Jamaican English, 2nd ed., Cambridge University Press, Cambridgeshire

• Fawcett, W. 1891, Economic plants, An index to economic products of the vegetable kingdom in Jamaica, Jamaica Government Printing Establishment, Kingston

• 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. 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

• Jacobson, M. 1958, Insecticides from plants : a review of the literature, United States Department of Agriculture (USDA), Washington D.C.

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

• Longwood, F. R. 1962, Present and potential commercial timbers of the Caribbean: with special reference to the West Indies, the Guianas, and British Honduras, U.S. Dept. of Agriculture Forest Service, Washington, D.C.

• 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