Mulga Trees for Desert Landscaping

Mulga trees (Acacia aneura) are native to Australia but can thrive in a desert landscape in the United States. Hardy in U.S. Department of Agriculture plant hardiness zones 8 through 11, mulgas tolerate extreme heat and survive temperatures as low as 15 degrees Fahrenheit. Sandy desert soils typically contain few nutrients and little water, but mulga trees thrive with minimal amounts of both.

Growing best in areas that receive full, all-day sunlight, mulga trees tolerate a large range of soil types, as long as the soil drains well and does not hold standing water. Sandy desert soils and sandy loam drain the best and usually result in optimum tree health and growth. Mulga trees grow up to 25 feet tall and have an almost equal spread. So plant them where they will have enough space at maturity. Each mulga's upright trunk and branches are stiff and brittle, making wind damage a possibility. A planting site protected by walls, fences or buildings can help buffer the prevailing wind and prevent damage from it.

Tall mulga trees can provide much needed shade in a desert landscape, with the shade protecting people, a home or less sun-tolerant small plant species. The trees can be used as specimen plants in a xeriscaped lawn, growing well in fast-draining sandy soil covered with landscape rocks. Bushier forms of the trees thrive in areas where irrigation isn't possible, such as certain desert environments. When planting a mulga tree, put it in the spot that will be its permanent location because a mulga almost 4 inches tall can have a taproot almost 10 feet long, making the tree difficult to move with its entire taproot.

Mulga trees can live more than 50 years and require almost no maintenance after they are established in their locations. Although drought-resistant, the trees grow more quickly and flower more abundantly when irrigated. During their first year of growth in a desert landscape, irrigate mulga trees every 10 days when the weather is dry, providing 2 to 3 inches of water per irrigation session. This initial irrigation program ensures healthy root establishment. No watering is necessary after the trees are established, but water runoff from nearby landscape areas won't harm the trees and may improve their growth. Mulga trees don't require pruning or fertilization, and they do not suffer from pest or disease problems.

Yellow flowers emerge from the trees periodically when the weather is warm, adding a touch of color to the landscape. Mulga foliage remains evergreen, and so the trees provide year-round interest in a desert garden. After flowering, the trees produce 1 1/2-inch-long, reddish brown seedpods. The trees' narrow leaves measure no more than 3 inches long and are silver-gray when mature and brown when young. Most mulgas develop a single trunk and dense canopy of branches and leaves. If the trees receive no extra irrigation and live in drought conditions primarily, then they may develop multiple trunks and be shorter and bushier than normal.