Guaiacum officinale aka Guaiacum

Guaiacum officinale, or lignum vitae, is a small evergreen tree. It belongs to the Zygophyllaceae family and grows slowly. Kew lists its native range from Florida through the Caribbean. The range also runs from Panama to Venezuela and Peru. It grows in both dry and damp coastal woods. It also grows on soil laid down near the coast. Heavy harvests have reduced wild stocks across its range. Useful Tropical Plants cites an Endangered listing from 2011.

Garden references give heights of about 30–33 feet [9–10 metres]. Wider accounts give 10–39 feet [3–12 metres] as the range. Its crown can spread to 33 feet [10 metres]. The trunk and limbs bend, forming a dense crown. Young bark is smooth, with a grey and brown tone. It grows darker and rougher as the tree ages. Thin twigs bear many short shoots with a knotted look. The leathery leaves stay on the tree year-round. They grow in opposite pairs and have a pinnate form. Each leaf has rounded or oval leaflets in green shades.

Flowers appear from spring into the early part of summer. Small groups grow where leaves meet the stems. Each flower has five broad petals and spans half an inch. The blue-purple blooms lose colour as they age. Some turn almost white while newer blooms remain blue. The mix of shades gives the crown much of its appeal. Sources describe yellow to orange fruits, but differ on details. Virginia Tech describes capsules that split to show shiny red seeds. PFAF describes heart-shaped fruit with red flesh and black seeds.

This tree needs sun and a warm, frost-free site. PFAF places it in USDA zones 10–12. Temperatures near 1°C or below may kill it. It grows in sand, loam, or clay with good drainage. Fertile soil that holds moisture suits it well. It accepts acid, neutral, and mildly alkaline soils. Once rooted well, it can cope with long dry spells. It also tolerates salt spray and some salt in soil. These traits suit warm gardens near the sea.

People value its hard, dense wood and its resin. The resin flavours cakes and chewing gum. It also helps keep edible oils from becoming acidic. Wood and resin have a long history of medicinal use. Useful Tropical Plants says those treatments are now largely obsolete. The sources report no known hazards, rather than proven safety.