Forget the image of magnolias as a tree suitable only for warm, southern climes. The magnolia tree family includes over 150 species, many of them hardy to U.S. Department of Agriculture plant hardiness zone 4. Almost all species are native to Asia and may range in size from small shrubs to huge, long-lived trees growing to 50 feet tall or more. The key to successfully growing magnolias is to choose a species adapted to your climate and give it the right growing conditions.
Types of Magnolias
Evergreen magnolias (Magnolia grandiflora) are truly spectacular in the right climate and location. Hardy in USDA zones 8 through 10 only, these trees have large, glossy leaves and creamy flowers. They bloom almost year round. The trees can grow up to 50 feet tall with wide-reaching limbs and roots. If you live in the South and have the space, consider growing one of these trees. Evergreen magnolias do have some drawbacks, of course. The leaves drop year-round, creating a constant chore. The roots are shallow and have been known to lift or crack pavement and patios. Because of their size, evergreen magnolias are difficult to prune or spray for disease. The trees create a dense shade, under which no grass and few plants will grow. Try Sweet Bay (M. virginiana) for a smaller tree with greater cold hardiness.
In cold climates, try the popular saucer magnolias (Magnolia × soulangeana). These trees are generally hardy in USDA zones 5 through 9 and produce lovely pink, white, mauve or purple blooms that resemble tulips. Saucer magnolias prefer moist, but well-draining, acidic soil and partial sun. They are sensitive to late spring frosts and cold, harsh winters. Plant saucer magnolias in an area protected from winds and cold pockets. Saucer magnolias can grow up to 30 feet tall, but most stay under 25 feet, especially at the northern extremes of their hardiness zones.
Star magnolias (Magnolia stellata) have a shrub-like form and generally grow 8 to 15 feet tall. Of all the magnolia species, star magnolias are the most cold hardy (zones 4-8) and the most adaptable to soil conditions. Star magnolias have open, star-shaped blooms in a variety of colors that usually appear in early spring before the leaves unfurl.
No matter which species you choose, select the planting site carefully. Magnolias resent being moved. Choose a site with plenty of room for large species. Dig a hole as deep and twice as wide as the root ball. Stake single-trunk species, especially if you live in an area with cold, windy areas. Place the stake in the planting hole before you add the tree. Make sure the top of the root ball is sitting at soil level, not lower. Fill the hole halfway and add some water. Allow it to drain and fill it with the remaining soil, tamping down very gently.
Magnolias have soft, delicate roots that are easily damaged. Keep an area under the tree grass-free and don’t plant anything there. Spread a 2 to 3 inch mulch over the area instead. Water magnolia trees once a week in dry, hot conditions. Magnolias need reasonably moist conditions, but they don’t like wet feet.
Prune magnolias in late summer or early winter. The trees tend to bleed sap in spring. Magnolias don’t need a lot of pruning and pruning wounds tend to heal slowly. Prune magnolias only to remove dead or diseased branches, or branches that are rubbing together. Prune minimally to shape the tree and control its size.
Fertilize magnolias in spring as new growth appears with a balanced fertilizer. Apply ½ to 1 cup of 10-10-10 fertilizer around the base of the tree, depending on the age and size of the tree. Larger trees need more fertilizer.
Potential Pests and Problems
Magnolias can be afflicted with a host of problems, including powdery mildew, leaf spot, root rot, anthracnose, canker, weevils, thrips, snails and scale. Keeping the tree healthy is the best defense against these problems. Make sure the soil is rich, slightly moist and well-draining to support vigorous growth. Prune minimally since pruning cuts can serve as an entrance point for disease.
Varieties Worth Considering
- ‘Alexandrina’ is a saucer magnolia with blooms that are rose-colored on the outside and white on the inside.
- ‘Rustic Rubra,’ also a saucer magnolia, has pink blooms with a reddish tint.
- ‘Leonard Messel’ is a hybrid star variety that grows taller than most other star varieties.
- Magnolia macrophylia is grown as much for its foliage as its flowers. Hardy in USDA zones 5 through 9, the tree grows 30 feet tall with leaves that can grow to 3 feet long.
To learn more about magnolias, visit the following links:
Growing Southern Magnolia from the University of Georgia.
Magnolias are Worth the Effort from Utah State University Extension