Kobus Magnolia – Magnolia kobus

Commonly called Northern Japanese Magnolia. USDA hardiness zones: 5 through 8A

Kobus magnolia is a striking tree in summer or winter. Dropping its large, six-inch leaves in fall without any spectacular display of color, Kobus Magnolia forms an attractive winter specimen with its rounded silhouette and multiple trunks originating close to the ground. Supposedly grows 30 to 40 feet tall but is most often 25 feet or less in an open, sunny landscape site and is capable of reaching 75 feet in height in its native forest habitat. In an open site, spread is often greater than height with 25-foot-tall trees 35 feet wide if given the room to grow unobstructed. Branches gracefully touch the ground on older specimens as the tree spreads, in a manner not unlike open-grown Live Oaks [1].

This Kobus magnolia, grown from seed, is 46 years old

Leaf blade length: 4 to 8 inches. Flower color: pink; white. Flower characteristics: pleasant fragrance; spring flowering; very showy. Fruit shape: elongated; irregular. Fruit length: 1 to 3 inches. Fruit covering: dry or hard. Fruit color: pink; red. Fruit attracts birds; no significant litter problem; showy. Bark is thin and easily damaged from mechanical impact, Branches droop as the tree grows, and will require pruning for vehicular or pedestrian clearance beneath the canopy. Can be grown with, or trainable to be grown with, multiple trunks. Needs little pruning to develop.

Image: Kobus Magnolia

Drought tolerance: moderate / Aerosol salt tolerance: low / Soil salt tolerance: poor
Roots: surface roots are usually not a problem. Kobus Magnolia has winter interest due to its unusual form and persistent fruits. The lightly-fragrant blooms which appear in spring before the new leaves unfold are ivory-colored to pale pink and four inches in diameter. Young trees flower poorly. The pink fruits which develop split open to reveal bright red seeds, which sway from slender threads before dropping to the ground.

Kobus Magnolia should be grown in full sun or partial shade on any well-drained soil. Probably not for poorly-drained areas but supposedly tolerant of soil with an alkaline pH. The cultivar ‘Wada’s Memory’ has black-green leaves, large, six-inch blooms and an upright or columnar growth habit (at least in youth). It will be available at selected nurseries. Propagation is easily done by cuttings. No pests or diseases are of major concern but occasionally bothered by scale as are other Magnolias [1].

References:
1. USDA NRCS Fact Sheet ST-379
2. USDA, ARS, National Genetic Resources Program. Germplasm Resources Information Network
3. Northern Japanese Magnolia, Morton Arboretum acc. 532-52-1 & 798-54-2 photos by Bruce Marlin

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