Guaiacum sanctum aka Guaiacum

Guaiacum sanctum is an evergreen tree, also called lignum vitae or holywood. It belongs to the Zygophyllaceae family. Its native range covers Florida, Mexico, Central America, and the Caribbean. It grows in lowland tropical woods, often on dry, exposed ground. Some sites dry out for part of the year. Harvesting and land clearance have reduced wild populations. Useful Tropical Plants cites an Endangered listing from 2011.

This slow-growing tree often forms several trunks near the ground. In gardens, it usually stands 8–12 feet [2.4–3.7 metres] tall. Its spread reaches 8–12 feet [2.4–3.7 metres]. Larger trees can reach 30–35 feet [9.1–10.7 metres]. Useful Tropical Plants reports rare trees reaching 66 feet [20 metres]. The crown may be rounded and dense, or open and spreading. Branches can droop, and the tree has no thorns. Bark varies from brown with gray patches to pale gray. It peels in patches as the tree ages.

The dark green leaves feel leathery and have a glossy surface. Each pinnate leaf carries three to five pairs of leaflets. Leaves sit opposite, or nearly opposite, along the stems. They stay green rather than taking on fall colors. Blue to violet flowers form clusters at the branch tips. Older flowers fade to a paler blue. Bloom peaks in spring, but flowers can appear year-round. Small yellow-orange fruits follow, with five wings around each capsule. Fruit peaks in summer, though some can appear year-round. Flowers and fruit may share the tree at once.

Grow it in full sun or part shade. Missouri Botanical Garden gives USDA zones 10–11 for outdoor growing. Useful Tropical Plants warns that temperatures near freezing can kill it. It accepts sand, loam, or clay, and acid or alkaline soils. Good drainage matters, despite its tolerance of wet and dry ground. Moderate, steady watering suits garden plants, while established trees tolerate drought. Wind and salt spray cause few problems. These traits suit coastal gardens, lawns, patios, and containers. Slow growth also allows use as bonsai. Pruning helps build a strong branch structure. The cited garden sources report no major pest or disease problems. Roots and fallen leaves or fruit cause few problems.

The heavy wood sinks in water and has served many practical uses. These include mallets, gears, bowling balls, and ship parts. Sources record medicinal uses for the wood and resin. Leaves have also served as a soap substitute. Plants For A Future lists no known edible uses. It and Useful Tropical Plants report no known hazards. That does not establish safety for people or pets.