Common name: Spanish elm

Spanish elm or Salmwood is a timber and honey tree native to tropical America, its natural range extending from Mexico, through Panama and the Caribbean, to northern parts of South America.

It is highly variable in its flowering habit, timber quality and climate adaptation, as revealed in African trials using propagation material sourced from different areas within its native range. Based on these trials, the most promising selections for high-value timber come from seasonally dry regions.

It may attain a height of up to 40 m (130 ft) in forests habitats, though it is more commonly 15 to 20 m (50 to 65 ft) tall on open sites and develops a slim, straight trunk, sometimes with a small buttress on large trees supporting a compact crown.

Leaves are oblong or elongated oval, 15 to 18 cm (6 to 7 in) long, thin, yellow-green and slightly glossy on top, paler and finely haired underneath. They give off a smell of garlic when crushed and are semi-evergreen to deciduous, with leaf-fall in the dry season followed by new leaf growth in the rainy season.

Flowers are creamy-white and small but sweetly fragrant and showy when abundant. Flowering is induced by short days, with blooms in late autumn, winter, and early spring in most tropical regions. The flowers open at night to be pollinated by nocturnal insects. 

Fruit develop and mature with the flower petals intact, which later dry and become papery wings that aid seed dispersal.

Use

Spanish elm produces a medium-weight wood, averaging 600 kilograms per cubic meter, with moderate to high natural resistance to rot and decay. This puts it in the moderately durable hardwood category, fit for indoor and outdoor use. The heartwood is pale green- to olive-brown with dark streaking, becoming pale golden-brown to brown on exposure and is fairly easy to work.

The logs are sawn into beams and planks used in light construction, interior joinery, flooring and for making furniture and cabinets. Selected logs are sliced for decorative veneer or are used for manufacturing plywood. The small-diameter roundwood and branchwood pieces are used mostly for making charcoal.

Spanish Elm is a major nectar source for honeybees in Belize and a moderate to minor source in the Dominican Republic and Trinidad, with honey production averaging around 165 lbs (75 kg) per colony per season.

In its native range, it is sometimes planted to shade coffee (Coffea arabica) because of its fast growth and light, open branching habit, allowing sunlight to filter through the canopy. It is also commonly cultivated as an ornamental because of the showy display of its white flowers in winter.

Climate

It grows naturally in humid tropical lowland to mid-elevation climates, generally in frost-free areas with annual lows of 16 to 25°C, annual highs of 26 to 35°C, annual rainfall of 1200 to 3500 mm and a dry season of 5 months or less. Trees reach their best development in areas with annual rainfall of 1800 mm or more.

Growing

New plants are usually started from seed, which lose their viability quickly and should be sown soon after extracting from the fruit. They can be kept for longer under cold, dry, air-tight conditions. Performs best on free-draining clay and loam soils of a slightly acid to alkaline nature, generally with a pH of 6.5 to 8.0, and on sites with full sun exposure. It is intolerant of saturated soils and shade conditions.

Problem features

Spanish elm is listed as a weed in at least one reference publication. It is a major weed in Tonga and Vanuatu, in the Pacific. A successful coloniser of disturbed sites, it produces many wind-dispersed seed that can travel afar and germinate readily.

It is also known for having vigorous roots, surface roots, particularly on shallow soils, and for sending up root suckers.