Bigleaf Magnolia Plant Profile

Bigleaf Magnolia (Magnolia macrophylla)

60548141@N00 / Flickr / CC BY 2.0

The bigleaf magnolia (Magnolia macrophylla) is a stunning addition to any native garden. A deciduous magnolia tree species, the leaves are the largest simple leaves found in North America, measuring up to three feet long and one foot wide. Its fragrant white flowers are equally impressive––and equally massive with a length of 12 inches. You may also know the bigleaf magnolia by its other names: the great-leaved magnolia or the large-leaved cucumber tree.

Botanical Name Magnolia macrophylla
Common Name Large-leaved cucumber tree
Plant Type Tree
Mature Size 30–40 feet tall and 20–30 feet wide
Sun Exposure Full sun to part shade
Soil Type Moist, well-drained
Soil pH Acidic to neutral
Bloom Time Late spring to early summer
Flower Color Creamy white with purple petal bases
Hardiness Zones 5–8
Native Area Caribbean, eastern Mexico, southeastern United States

How to Grow Bigleaf Magnolias

Despite their showy nature, bigleaf magnolias are easy to care for when grown in optimal conditions. They do not suffer from any serious pests or diseases, nor do bigleaf magnolia trees require any regular pruning to maintain their shape. To prevent sap from bleeding, some growers opt to prune their bigleaf magnolias in late winter or late summer.

Bigleaf magnolias only begin to produce blooms once they reach 12 years of age. When pollinated, the flowers produce elongated red fruits measuring one to three inches. This fruit is popular with birds and other wildlife.

The extraordinary leaves and blossoms on the bigleaf magnolia make it a show-stopper when planted in a yard, but because the leaves are so large, raking can be quite a chore in the fall.

Light

Magnolia macrophylla needs a site that has full sun to part shade. Two to five hours of direct sunlight each day is ideal.

Soil

Bigleaf magnolia trees prefer conditions that mimic their native habitat in alluvial woods and piedmont. Loamy, rich soil that drains well is ideal. If your soil does not meet these requirements, consider using mulch. Bigleaf magnolias grow best in soil that is slightly acidic to neutral.

Water

Bigleaf magnolias do not like soil that is too dry or too wet. Always let the soil to dry out between waterings, but never allow it to stay dry for too long. Using a water ring to water the tree is ideal as it establishes itself; once the tree is well-rooted, water only when the top inch of soil is dry to the touch. Bigleaf magnolias grown in exceptionally well-draining soil will need more frequent watering than trees grown in more slow-draining soil types.

Temperature and Humidity

The bigleaf magnolia is originally from the southeastern United States, eastern Mexico, and the Caribbean. It prefers climates that have similar conditions, doing best in zones five to eight.

One unique requirement of bigleaf magnolia trees is a location that does not experience much wind or, failing that, being planted in a place that shields them from strong winds. Because the leaves of this tree are so large, they are easily damaged and torn by strong gusts of wind.

Fertilizer

When grown in the rich soil they prefer, bigleaf magnolias may not need fertilizer. Signs that fertilizer is needed include weak new growth in the spring and significant dieback. Use a slow-release fertilizer with a balanced formulation and apply it during late spring or early summer

Propagating Bigleaf Magnolias

Most growers prefer buying bigleaf magnolia trees from nurseries, but they can also be grown from seed. Collect ripe, fallen fruit from the ground; remove the flesh, leaving only the seed. Cleaned seeds can be stored in an airtight container in the refrigerator. Sow the seeds in the fall, but be aware that bigleaf magnolia seeds are known for having low seed viability.

If you're not keen on trying your luck with the seeds, bigleaf magnolias can also be propagated via rooting softwood cuttings in the summer, grafting, and layering.

Varieties of Bigleaf Magnolias

This tree has been classified as Magnolia macrophylla. The species name of macrophylla comes from the Latin words meaning "large leaves." It is in the Magnoliaceae family.

The bigleaf magnolia has been further split into three different subgenera. They are Magnolia macrophylla subsp. ashei (Ashe magnolia), M. macrophylla subsp. macrophylla (bigleaf magnolia) and M. macrophylla subsp. dealbata (Mexican bigleaf magnolia).

History of Bigleaf Magnolias

The bigleaf magnolia was first described by Andre Michaux, a French naturalist who encountered the tree near Charlotte, North Carolina. Both illegal and legal collection has decreased the natural population of bigleaf magnolias, making it a threatened species in North Carolina and endangered in Ohio and Arkansas.