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Scientific: Eucalyptus coolabah (closely related to Eucalyptus microtheca)
Common: coolabah
Family: Myrtaceae
Origin: Widely distributed across Australia in riparian zones

Pronounciation: Ewe-ka-LIP-tus COO-la-bah

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

Landscape Use: Moderate-sized tree for many Phoenix landscape uses from lawns and green spaces to urban street and parking lot tree.

Form & Character: Variably upright and spreading, often irregular in its spread, rugged.

Growth Habit: Evergreen, woody, broadleaf perennial tree, moderate growth rate to 30- to 40-feet tall with usually greater spread.

Foliage/texture: Juvenile leaves are disjunctly lanceolate to broadly lanceolate, dull grey-green to glaucous in color. Adult leaves are disjunct, narrowly lanceolate, 3-to 6-inches long to 1-inch wide, a dull grey-green in color. Coolabah's bark on its trunk is persistent, dark grey, thick, roughened and furrowed; medium texture.

Flowers & fruits: Umbellated, small, creamy white flowers, typically up to 7 per umbel on 1/2-inch long peduncles; fruits are pedicellate (pedicels to 1/4-inch long), valved capsule, small hemispherical or obconical (1/4-inch width and length), valves 3 or 4, strongly exserted.

Seasonal color: Glaucous blue green foliage all year creates feeling of space. Clustered white flowers in the summer.

Temperature: Very cold hardy to 6o to 10oF. Also, tolerant of high temperatures, even those associated with parking lot exposures.

Light: Full sun

Soil: Very tolerant

Watering: Infrequent deep summer irrigation.

Pruning: Prune and stake all eucalyptus vigorously when young, especially collabah as its habit is prone to be spreading, irregular and not strongly upright.

Propagation: Seed, difficult, requires a flooding pre-treatment for rapid germiniation.

Disease and pests: None

Additional comments: Eucalyptus coolabah is quite similar in apearance to Eucalyptus microtheca and for the most part in the Phoenix area they are landscape functional equivalents, though Eucalyptus microtheca is more commonly seen. The main external difference between these two landscape trees is that Eucalyptus coolabah is often more wide spreading and has a more roughened phellum (bark) on its lower trunk.

Obscure taxonomic tidbit: The species name, coolabah, was first recorded by Australian European settlers in 1885-90, either from the Aboriginal words, “gulaba” or “gulabaa”.