Krugiodendron ferreum

Common name: Black ironwood

Other common names: Axe master, Ironwood, Leadwood

Names in non-English languages: French Spanish

Description

Black Ironwood is small landscape and minor fruit tree originating in the Caribbean, where it occurs in coastal as well as hilly areas. Its natural range extends from Melbourne, in Central Florida, south through the Florida Keys to the Eastern and Southern Caribbean, as far south as Bonaire and Curacao, and to Mexico and Honduras in Central America.

In coastal areas, it is typically a small tree 3 to 5 m (10 to 15 ft) tall with a slender trunk up to 15 cm (6 in) in diameter supporting a densely leaflet rounded crown. Inland and in the moist, hilly parts of its range, it may reach up to 17 m (56 ft) tall with a trunk 50 cm (20 in) in diameter. The bark is grey, smooth or lightly fissured, becoming scaly on mature trees.

Leaves oval, up to 6 cm (2.5 in) long, slightly notched at the tip, when young copper-red, with age becoming dark glossy green on top, dull green underneath and have a thin leathery texture. They are arranged near opposite along the ends of the branches and remain on the tree throughout the year.

Flowers small, greenish-yellow, borne in clusters of only a few arising at the sides of the branches. They bloom on and off throughout the year but are at their fullest from spring to summer and give-off a strong almond odour.

The flowers are followed by small roundish fruit up to 1 cm (0.4 in) long. These are green when young, becoming dark purple or near black when ripe and have thin, juicy pulp surrounding a single seed.

Use

The tree's small size, shapely form and lush green foliage make it an excellent candidate for a specimen or landscape tree, especially in tropical coastal areas on account of its tolerance to salt spray, drought and limestone soils. As a bonus, the fruit attract and sustain native birds and the flowers are actively worked by honeybees. 

The fruit are edible and the pulp, although scant, is juicy with a sweet grape and blackberry flavour, made more appealing by its dark purple colour. They can be eaten fresh out-of-hand, made into jam or jelly or soaked in alcohol, usually in white rum infused with spices such as clove and cinnamon, to make a potent and spicy local liquor. 

The wood, one of the hardest and heaviest known, is in the 1340 to 1420 kgs per cubic meter (84 to 89 lbs per cubic ft) range and has good natural resistance to rot and decay. However, it is brittle and the logs are in diameters too small to make sawing them into lumber practical. They are instead mostly used for posts and poles.

General interest

The second part of the botanical name, 'ferreum', comes from the the Latin word for iron, 'ferrum', 'in reference to the hardness of the wood.

Climate

Grows naturally in sub-humid to moderately humid subtropical and tropical climates, generally in areas with annual lows of 17 to 25 °C, annual highs of 26 to 35 °C, annual rainfall of 600 to 2000 mm and a dry season of 2 to 8 months. In Jamaica, it is found growing at elevations from near sea level up to 900 meters (3000 feet).

Growing

New plants are usually started from seed. Performs best on free-draining loam, sand and limestone soils of a slightly acid to alkaline nature, generally with a pH of 6.0 to 8.0 and on sites with full to partial sun exposure.

Problem features

Birds eat the fruit and disperse the seed, which germinate readily. However, there does not appear to be any record of it anywhere as a problem weed or invasive species.

The dark juice can permanently stain clothes and other fabric, as well as concrete surfaces such as driveways or sidewalks.

Where it will grow


References

Books

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

  • Little, E. L. et al. 1964 and 1974, Common trees of Puerto Rico and the Virgin Islands (2 volumes), Forest Service, U.S. Department of Agriculture (USDA), Washington D.C.

  • Record, S. J. & Hess, R. W., 1972, Timbers of the New World, Yale University Press, New Haven, Connecticut & Arno Press, New York

  • Thompson, R.S. et al. 2015, Atlas of relations between climatic parameters and distributions of important trees and shrubs in North America - Revisions for all taxa from the United States and Canada and new taxa from the western United States: U.S. Geological Survey Professional Paper 1650–G

Articles, Journals, Reports and Working Papers

  • Meerow, A.W. 1996, Native Trees for South Florida, University of Florida-IFAS Publication EES-57, Gainesville

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