A shrub, or with pruning, a multi-trunked, spreading to weeping tree.
Evergreen, but drought and freeze deciduous.
Very slow, possibly only 2.5"/year in the wild.
Usually 6' high and wide, but may eventually reach 16-20' high and 20-50 wide under
Five vividly dark blue to purple curved petals surround prominent yellow anthers. The flowers
may occur singly or in clusters.
Primary bloom occurs mid to late spring. Sparse blooms appear sporadically throughout the
rest of spring and summer.
Small, greenish-reddish-brown, narrowly winged capsules with 2-4 lobes, containing bright
Small green, oval leaflets grouped in pairs of 3-8. With insufficient water the leaflets
rotate their stems in high temperatures to so that they catch the sun on their edges to
minimize light and heat exposure.
Grey, crooked, no thorns. The branches on top of the shrub can be sparsely leaved with
insufficient water. The wood of Guaiacum genus plants is called Lignum vitae and is one of
the hardest, toughest, densest woods known, being heavier than water.
The flowers attract bees. The red seeds attract birds. The leaves are browsed by deer and
livestock. The plant is a host to the larvae of at least one species of sulphur butterfly.
Toxic / Danger:
Regions within Mexico, and possibly Guatemala, that have high summer rainfall and dry winters.
Cultivation and Uses
USDA hardiness zones:
9b-11. This plant is damaged below 25°F when mature. It is frost-sensitive when young and
should be protected from freezing in its first three years.
Yes, but this plant may lose its leaves in severe summer drought.
Full sun. Part shade causes the plant to grow leggy and sparsely leaved.
Locate this plant in all day full sun in well draining soil. The site should be large enough
to accommodate an eventual 6x6' size, with small shrubs or perennials used to fill in the
sides until this plant becomes large enough to spur their removal. It will grow in a
Well drained, gravelly, dry, low in organic content. Apply composted manure in winter to
Water after becoming established:
every 4-6 weeks in winter. Deep water
every 1-2 weeks in spring and summer for improved growth.
In its first three years, mulch the root zone in winter in regions with freezing temperatures.
First Year Care:
Do not fertilize. Do not prune. Protect from freezes.
Trim lightly in winter to control shape. This plant grows very slowly. Remove weeds by hand
under and within one foot of the canopy.
Seed, less than one month old and soaked in water; woody cuttings. Dried seed over one month
old is non-viable.
This plant is a member of the Caltrop family (Zygophyllaceae). Its slow growth does not
compete well with faster growing species. Other related species are Guaiacum officinale and
G. sanctum, both small, slow-growing trees valued for their wood, and like G. coulteri and
all other species in this genus, harvested to endangered status in their native region.
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Latest update: June, 2021.