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 to street tree medians. 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 a woody, evergreen 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: Silver blue lanceolate sickle-shaped leaves when young, blue-green lanceolate to ovate leaves when mature, 4 to 6 inches in length, trunk variable from smooth white to chocolate brown, usually with gray mottled 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: Silver blue foliage all year creates feeling of space. Clusters of white flowers in the summer.

Temperature: Very hardy!!!! from 10oF to 125oF or hotter, even tolerant of high air and 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 endeavor to remove stakes no later than 12 months after transplanting from nursery container.

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, 'Blue Ghost', is an outstanding locally available cultivated selection from Desert Tree Farm in Phoenix, AZ, 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.

E. microtheca is one of many eucalypts with medicinal value.