Magnolia bushes are used as a specimen planting in landscape design. They are known for their beautiful spring blossoms, which open in late winter to early spring (before the leaves appear). A late frost, however, can damage the flowers. This ornamental tree or shrub features 80 species in a range heights up to 80 feet. Depending on species and hybrid, there are magnolias suited to USDA hardness zones 3 through 9. Flower colors include white, pink and rose, as well as yellow, wine-red and purple.
One of the most popular species is the saucer magnolia, which can reach a height of 20 to 25 feet and a spread of 20 to 30 feet and is hardy in zones 5 to 9. The 'Lilliputian' saucer magnolia cultivar reaches a height of 12 to 15 feet and a spread of 10 to 18 feet. The crown shape of the saucer magnolia is round and irregular; the tree's growth rate is medium. Its saucer-shaped flowers--pink and creamy/gray white--are harbingers of spring. In autumn, its leaves turn yellow.
Magnolias do well in a site that receives full sun. where the soil is well-drained, organically rich loam or sand with a pH on the acidic side. It will grow in partial shade, but growth will not be as vigorous as in full sun. Magnolias should be planted in spring before new growth begins.
The magnolia tree/bush can be attacked by 15 different species of fungi that cause leaf spot. In most instances chemicals will not need to be applied. Symptoms of leaf spot are brown, yellow or black dead spots on the leaves. Spots may grow together--forming a larger dead spot on the foliage. The leaves will fall off; they should be raked up and destroyed (not put in your compost bin).
Verticillium wilt--another disease to which the magnolia is susceptible--is caused by the fungus Verticillium dahliae. The fungus survives in the soil and roots of an infected tree. The disease is spread when the soil is tilled or cultivated, by watering or rain, and by infected pruning tools. Symptoms are wilted leaves sticking on one or several branches. Symptoms progress to other branches of the tree--verticillium wilt can kill a magnolia bush; there is no known treatment.
Cankers are another fungal disease that can attack the magnolia bush. Cankers, or lesions, appear on the branches and stems of the bush. The branches die, and they should be pruned out. To avoid fungal disease, maintain a healthy tree by following a fertilization program and watering the tree when necessary. Also, avoid injuring the tree in any way, as wounds provide an entryway for bacterial/fungal diseases.
The most common pest to be found on the magnolia is various types of scale that infest the twigs of the bush. Magnolia scale--which appears as brown bumps--is quite common. According to the United States Department of Agriculture, "Overwintering scales are usually controlled with horticultural oil applied in the spring."