How to Grow Magnolia Grandiflora (Southern Magnolia Trees)

Close up of the flowers of the Magnolia grandiflora, commonly called Southern magnolia or Bull bay

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The southern magnolia (Magnolia Grandiflora) is a beautiful, adaptable evergreen tree known for its large, fragrant, white flowers and lustrous dark green leaves that grow on the conical crown. The fall fruit will attract birds to your landscape.

It isn't the largest species, typically growing up to 50 feet tall, but it has a dense canopy and a shallow root system. The tree needs plenty of space, requires mulch to prevent erosion problems, and it isn't a good choice if you want to grow underneath it. Plant these trees in late spring or early fall, and be aware it can take 10 to 20 years for them to reach their full size.

 Botanical Name Magnolia grandiflora
Common Name Southern Magnolia, Bull Bay, Big Laurel
 Family Magnoliaceae
 Plant Type Perennial, Tree
 Mature Size 60-80 ft. tall, 20 - 40 ft. wide
 Sun Exposure Full sun, Partial Shade
 Soil Type Moist, Well-drained
 Soil pH Acid, Neutral, Alkaline
 Bloom Time Spring, Summer
 Flower Color White, Cream
Hardiness Zones 6-10, USA
 Native Area Southeastern United States

Magnolia Grandiflora Care

Southern magnolias are attractive and relatively easy-to-grow specimen trees—just be sure to select a site that is sheltered from strong winds and offers them ample room to grow. They are often planted in rows to act as a privacy screen or to define property lines. Because of their messy leaf drop in the spring and fall, they aren't always a good choice for a lawn. Planting in an ornamental bed means you can use the robust leaf debris can as a natural mulching material.

You can plant container-grown trees at any time, and those bought balled and burlapped are usually transplanted sometime between August and October. Transplant shock is common with this species, so don't worry if the tree sheds many leaves during its first growing season.

Light

Southern Magnolias do best in partial shade, particularly if soil conditions aren't all that moist. Once established, they can do well in a full sun position in moist, rich soils. Ideally, your tree should receive at least four hours of unfiltered sunlight a day. In the winter months, in northern states, it will need protection from too much direct sunlight.

Soil

Southern magnolias do best in moist, well-drained, loamy, acidic, and fertile soils. However, they can tolerate a wide range of conditions and pH levels. Overly dry or prolonged waterlogged conditions and high alkalinity aren't appreciated.

Water

Providing your southern magnolia has ample room for root expansion and the soil is not a poor, dry type, it will demonstrate drought tolerance.

When first planted, the tree will need daily watering and then weekly after the first couple of months. Once established, water frequency will depend on soil drainage and regional rainfall. Mulching around the planting area is beneficial—just avoid allowing the mulch to touch the tree's trunk.

Temperature and Humidity

Southern magnolias prefer temperate and humid semitropical climes. Extremes of temperatures are not good, and even a light frost easily damages seedlings.

Fertilizer

Fertilizing three times a year—in spring, summer, and fall—is beneficial once your southern magnolia starts to produce new growth. By the fourth or fifth year, unless your tree is in particularly infertile soil, its sprawling roots should be able to find sufficient nutrients themselves.

Types of Magnolia Grandiflora

The southern magnolias popularity means there are many cultivars, with some that flower early and others with a smaller growth habit or thicker canopy. Some popular examples include:

  • Magnolia grandiflora 'Edith Bougue': One of the most cold-hardy cultivars, it has a pyramidal form that grows tighter and denser as it ages, and it typically reaches up to 30 feet tall.
  • Magnolia grandiflora 'Hasse': With its tight, columnar form, this cultivar works well for use in smaller spaces or in rows for screening. It typically reaches up to 40 feet tall.
  • Magnolia grandiflora 'Little Gem': This award winner is an excellent option if you are looking for a dwarf magnolia. One of the smallest cultivars, it is typically grown as a shrub and doesn't often grow higher than 25 feet. Although the leaves and flowers are small, they are still attractive, and the tree blooms abundantly from a young age.

Pruning

If you want to tidy up your southern magnolia and encourage a tight, compact form, you can prune it after the blooming season is over. Do this before winter—dormant magnolia branches don't heal easily. Avoid pruning the lower limbs to allow a more open and natural form and to prevent disease-inducing stress and suckers from forming.

Propagating Magnolia Grandiflora

It is possible, but sometimes tricky, to propagate southern magnolia from cuttings. If you plan to try this, there is some general guidance to be aware of:

  1. Select a six-inch semi-hardwood cutting with at least a few leaves from young stock during the summer months
  2. Apply a rooting hormone to improve success rates
  3. Place in a moist, well-drained rooting medium that is at least 4 inches deep
  4. When transplanting the cutting, take care not to damage the fleshy and delicate roots

How to Grow Magnolia Grandiflora From Seed

If you want to grow a southern magnolia from seed, try these tips:

  • If you are collecting seeds from an existing tree, look for red, oily, fleshy, ripe ones
  • Clean and store seeds in a cold, moist storage space. Stratifying the seeds for at least 60 days is beneficial.
  • Sow in a cold frame in late winter. Germination can take up to 18 months.
  • When the seedlings are large enough to handle, move them into a light shade position. Keeping them in a cold frame or greenhouse for their first full winter is beneficial.
  • Plant out when the seedlings are at least 6 inches tall, mulch well, and protect for the first couple of winters.

Common Problems With Magnolia Grandiflora

Southern magnolia are known for being relatively pest and disease-free. However, if conditions are not right, problems are possible.

Leaf Spot

Certain fungi and bacterium can cause leaf spots and blights. These include Septoria spp, Cladosporium spp, and Coniothyrium spp. Although it can look unsightly, they don't often cause any major damage. Promptly clearing away infected fallen leaves can help to control the problem.

Dying Branches

Canker diseases and Verticillium wilt can kill off branches. Manage this by pruning out the problematic branches and ensuring the tree is healthy, well-nourished, and watered.

FAQ
  • How fast does Magnolia Grandiflora grow?

    Depending on conditions, this species has a slow to medium growth rate. Typical annual growth is from around 12 to 24 inches.

  • Are southern magnolias easy to grow?

    Part of the popularity of this species is that they are adaptable to a wide range of conditions. Southern magnolias are relatively low maintenance, providing they are not growing in a region with extremes in temperatures or prolonged droughts.

  • Are southern magnolias a good choice for small yards?

    Magnolias have a shallow but spreading root system and higher than average leaf drop. This makes them a poor choice for yards with limited space. If you are keen to grow this species in a small garden, select a narrow, small cultivar like 'Little Gem'.