Guaiacum coulteri is a slow-growing, evergreen, crooked branching shrub. It is rarely seen taller than 5 feet in residential gardens, and it usually takes over 60 years to reach that height, although it is known to grow over 25' tall in its native region if left undisturbed. The wood of the Guaiacum species is one of the hardest, toughest, densest woods known, and is heavier than water. The leaves are dark green, small, oval, and pinnately compound, with 2 to 6 pairs of leaflets. With insufficient water, the leaflets rotate their stems in high temperatures so that they catch the sun on their edges to minimize heat stress (see picture). The flowers have five vivid blue to purple petals, with a primary bloom of clustered flowers in spring followed by sporadic single blooms until fall. The ripe fruit are yellow-orange to brown, winged capsules containing seeds coated with a bright red aril.
