Scientific: Eucalyptus microtheca
Common: Coolibah
Family: Myrtaceae
Origin: Widely distributed in northern Australia in open woodlands, floodplains, seasonally flooded areas, and the edges of swamps. Coolibah has been introduced and possibly naturalized in Egypt, Iran, Iraq, Nigeria, Pakistan, Sudan, and Tanzania.

Pronounciation: Ewe-ka-LIP-tus my-crow-THEE-ka

Hardiness zones:
Sunset 5, 6, 8-24
USDA 8-11 (arid and semi arid regions are best)

Landscape Use: Coolibah is a medium to large tree for many Phoenix landscape uses from xeric gardens, urban parks to street tree medians. However, it becomes too large for most residential landscapes. This wonderful tree is arguably one of the most heat tolerant trees that can be grown in the Phoenix area. Our research has shown that planting it in street or parking lot medians results in limited loss of overall productivity (unlike most other landscape tree taxa).

Form & Character: Variably upright, rugged to rounded with age, majestic and reserved because of its glaucous tint.

Growth Habit: Coolibah is an evergreen, woody broadleaf perennial tree that is a moderate fast grower to 30 to 60 feet with somewhat lesser spread. It is upright and narrow when young to more spreading with age.

Foliage/Texture: Leaves are glaucous gray-green to blue-green, lanceolate to ovate leaves when young, gray to silver-blue, sharply lanceolate, slightly falcate (sickle-shaped), 4 to 6 inches in length when mature, trunk variable from smooth white to chocolate brown, usually with gray mottled transitional patches; medium texture.

Flowers & Fruits: Many clusters of very small creamy white flowers, insignificant because of size, seed capsules in clusters, 3 to 5, small (ergo, the latin name microtheca or small cap).

Seasonal Color: Glaucous foliage all year creates feeling of space. Clusters of white flowers in the summer.

Temperature: Very cold and heat tolerant, from 10^oF to 125^oF or hotter, even tolerant of high root-zone temperatures associated with parking lot exposures.

Light: Full sun, any exposure.

Soil: Very tolerant.

Watering: Infrequent deep summer irrigation is best.

Pruning: Young trees should be pruned and staked vigorously, though one should always endeavor to remove stakes no later than 12 to 18 months after transplanting from nursery containers.

Propagation: Seed

Disease and Pests: None

Additional comments: Coolibah is an absolutely superb eucalypt for the Phoenix area that is able to endure and even flourish in the most difficult locations (such as an asphalt-covered parking lot); however, its form is variable because of seed propagation. Select only the most upright, silver-blue leaved forms for urban use. One example, the cultivar 'Blue Ghost', is an outstanding locally available cultivated selection from Desert Tree Farm in Phoenix, Arizona, that has striking silver blue foliage and a mostly upright form. As with all eucalypts, be careful and avoid transplanting container grown specimens that have deformed or pot-bound root systems.