Picrasma excelsa aka Bitter Ash

Picrasma excelsa, or Jamaican quassia, is a tropical tree. It sheds its leaves and belongs to the Simaroubaceae family. Its native range spans Central America and the Caribbean. It also spans the north of South America. Kew also records it in Ecuador and eastern Bolivia. It grows in tropical regions with a dry season. Wild trees grow in hill pastures and small, remaining woods. They also grow by roads, in tropical forests, and near water.

Grown trees reach about 66 feet [20 metres] in height. Their spread can reach 49 feet [15 metres]. The tree grows at a moderate rate. Broader accounts give heights of 20–82 feet [6–25 metres]. It does not keep its leaves year-round. Its wood ranges from white to pale yellow. The wood is light and soft, and splits with ease. The supplied accounts give no clear details about flowers or fruit. They give no details on leaf shape or bark texture.

This tree needs sun and does not grow in shade. It prefers fertile sandy loam with plenty of humus. The soil should hold moisture but also drain well. Sandy and loamy soils both suit it. It accepts soil that is slightly acid or slightly alkaline. Neutral soil suits it too. PFAF lists USDA hardiness zones 10–12. Growers can sow seed as soon as it ripens. They can also grow new trees from semi-ripe cuttings.

People have long used Jamaican quassia as medicine. They have also used it to kill insects. In South America, growers raise it chiefly for medical use. Past uses include treating fever, poor appetite, and gut complaints. These uses do not prove that home treatments are safe. The bark has quassin and other bitter compounds. In studies, some compounds have shown toxic effects on cells. A bitter bark extract adds flavour to drinks. It also flavours baked foods and sweets. PFAF names the inner bark as the edible part. Large doses can irritate the stomach and cause vomiting.

Bark products also kill insects or keep them away. Reported targets include flies, aphids, woolly aphids, and red spider mites. These are bark uses, not records of this tree's pests. The sources give no details of the tree's own diseases. PFAF reports no weed potential. Loss of forests and heavy harvests threaten wild trees. Useful Tropical Plants cites a Vulnerable listing from 2011. That old finding does not confirm its current status.