Saucer Magnolia Trees

Growing Information, Picture

Alexandrina is a saucer magnolia (image). It is one of the many trees on the Smith college campus.
Magnolia x soulangiana 'Alexandrina' is one of the saucer magnolias. David Beaulieu

Botanical Information for Saucer Magnolia Trees

The plant taxonomy of saucer magnolia trees is Magnolia x soulangiana. These magnolias are hybrids, derived from crossing M. denudata with M. liliiflora. They are grouped with the deciduous flowering trees.

Plant Traits

These magnolia trees reach a height of 20 to 25 feet, with a similar breadth. The mildly-fragrant, pinkish-white blooms, which appear before the leaves, are large (up to 10 inches across).

They open up from furry buds and are among the most popular spring flowers in North America. The size and shape of the blooms are what suggested the common name for these magnolia trees. The flowers bloom in April in USDA plant hardiness zone 5, for example. Popular cultivars of this plant are:

  • 'Alexandrina' (15 to 18 feet tall, with pink flowers), which is also called "Alexander's magnolia"
  • 'Bronzzonii' (20 to 30 feet, with white flowers)

Growing Information for Saucer Magnolia Trees

These highly-valued plants can, unhappily, be subject to a number of problems, depending on where you live. This means that they may not be the best choice if you desire low-maintenance landscaping above all else, because you may need to give them some care once in while (beyond the usual jobs such as watering and cleaning up plant debris in the fall). The following are examples of some of the plant-care issues that you may face with them:

One aspect of magnolia care is more about looks than plant health. Saucer magnolia trees can sometimes produce multiple stems. For the grower who wants a "tree look" rather than a "shrub look," this is a problem. You can correct it through pruning so as to favor one, dominant trunk. Such drastic pruning may be done while the tree is still young.

You may also shape the crown in later years by pruning lightly after the flowering period.

Saucer magnolia's tendency to lose flowers to early spring frosts can also be a problem. Sometimes, the flower buds never open, due to frost damage. But if you avoid giving these magnolia trees a southern exposure, you may delay blooming long enough to get past the period of frost danger. To avoid southern exposure, plant on the North side of your house or to the North of established pines, for example. As a bonus, the blooms look great against a green background of Eastern white pines.

Seeing brown leaves on a plant when it should be bearing nice, lush, green leaves is a nightmare for gardeners. When saucer magnolia trees get brown leaves at a time of year when they should have a green color, the reason can be frost, dry conditions, or poor nutrition.

Sun and Soil Needs, Growing Zones

Grow this plant in a fertile, well-drained soil in full sun to partial shade, and keep the ground evenly moist. The soil pH of the ground in which they are growing should be 4.5 to 6.0, but err on the acidic side. This means that, if you do fertilize your tree, you may want to use a fertilizer that will make the soil somewhat more acidic, such as Holly-Tone.

The best time to fertilize is in spring. But if the ground is already acidic and reasonably fertile, you may be able to get by with not feeding this plant at all.

Saucer magnolias are best grown in USDA plant hardiness zones 4 to 9.

Uses for Saucer Magnolia Trees in Landscaping, Other Types

These trees make fine specimen plants, but they do not make good street trees, because they do not hold up well to road pollution. "Saucer magnolia" is a common name that is often used somewhat loosely. While it technically refers to M. x soulangiana, it is often used, as well, to refer to similar trees in the genus that also have large flowers. Examples include (with height, zone information, and flower color in parentheses):

  • 'Betty' (12 to 15 feet, zones 4 to 8, pink)
  • 'Forrest's Pink' (20 to 30 feet, zones 5-9, pink)

    Other kinds of magnolia trees include star magnolia tree (M. stellata, which may bloom a bit earlier), 'Jane' (another hybrid), sweet bay ( M. virginiana), and Southern (M. grandiflora). There are great differences between the varieties, not the least of which is seen in the range of sizes. The biggest of them is M. grandiflora, an evergreen type which grows to be 60 to 80 feet tall.