In Bloom: An Ancient Genus with Lovely Tulip-shaped Blooms

By Corinne Kennedy

Magnolia x soulangeana in Area H, near the pond’s southern end. (photo: Chie Iida)

The Seattle Japanese Garden is home to several plants of prehistoric lineage, including six trees in the genus Magnolia.   Magnolias belong to the relatively ancient botanical order Magnoliales, until recent decades considered to be the oldest order of flowering plants (angiosperms).  The fossil record reveals that this order emerged about 95 million years ago, and that magnolia trees and shrubs were native over a wide area for millions of years.  They remained relatively unchanged for much of that time.  Having evolved before most flying insects, they’re pollinated by beetles – and perhaps also by bees.  Their native range, much contracted, is now limited to eastern Asia and the Americas.   

All but one of the magnolias in our garden are the very showy spring-blooming hybrid, Magnolia x soulangeana (saucer magnolia, sometimes spelled Magnolia soulangiana), a vigorous, multi-stemmed small tree.  Created in early 19th century France by the deliberate crossing of two magnolia species, it’s deservedly popular for its ease of cultivation and its large, attractive, often fragrant spring blooms.  The parents, Magnolia denudata (Yulan magnolia) and M. liliiflora (lily-flowered magnolia), are both natives of China and were used in traditional Chinese medicine.  The former has long been revered in China as a symbol of purity and truthfulness, and both were planted in Japanese temple gardens.  Thus, it’s probable that naturally-occuring hybrids of the two species existed in Japan long before the French cross was made.  Vigorous and long-lived, Magnolia x soulangeana is not susceptible to the propagation and disease issues that affect its parents.

The beautiful tulip-shaped flowers of saucer magnolia. (photo: Aleks Monk)

The flower buds of saucer magnolia are large and fuzzy, winter’s showy promise of the flowers soon to emerge.  They open on bare branches, before the foliage.  Leaves are large, oval, untoothed, medium to dark green, and arranged alternately on the stems.  Fall color is yellow-brown.  Low-branched, this relatively small tree reaches about 25 feet tall at maturity (about 25 years), and usually spreads wider with age.  Its branches sweep upwards.  Brown seed pods containing small red seeds are sometimes formed.

Unlike many other magnolias, Magnolia x soulangeana begins blooming when very young, often when less than four feet tall.  Numerous cultivars (named forms, grown from cuttings, not seeds) have been developed throughout the world.  All have large spring flowers in various shades of white, pink & reddish-purple – usually more colorful on the outer sides of each petal.  Flowers are shaped like tulips, goblets, or cups and saucers, and spread widely when open.  Some cultivars are more fragrant than others.

Easy to grow, Magnolia x soulangeana is cold hardy to USDA Zone 4 (minimum temperature -30 degrees F) and rarely suffers from insect or disease problems.  Trees thrive and flower best in full sun or light shade – and in moist, fertile, well-drained, slightly acid soil.  However, with adequate drainage they tolerate less than ideal conditions, including urban pollution.  Somewhat drought-tolerant when established, they do best with occasional watering during our summer droughts.  To protect flowers and foliage from damaging late frosts, trees should be planted in areas without strong winds and out of early morning sun.  And because the fleshy roots are easily damaged, they should be planted in their permanent location. 

Our Seattle Japanese Garden has three unnamed hybrids (referred to simply as Magnolia x soulangeana) – one each in Areas D, H & Q.  Two additional trees (in Areas V & Z) are the named form M. x soulangeana ‘Grace McDade.’  Developed in Alabama, it has a loose, shrubby habit and very large flowers – white inside and lavender-pink on the outside.  It’s said to have the largest blooms of any cultivar – over 12 inches wide when open.  Most were planted in 1960, when our garden was created, or during its first decade.

Flowers and foliage of Magnolia kobus. (image: 1912 lithograph, M. Smith and J.N. Fitch, in Curtis’s Botanical Magazine, Vol 138)

The only other magnolia in our garden is the Japanese native, Magnolia kobus, known by the common name kobus magnolia – kobushi in Japanese.  It grows much taller than saucer magnolia, with an upright habit and a mature height of 30-40 feet.  It has slightly fragrant, star-shaped white flowers – but unlike saucer magnolia, doesn’t flower well when young.  It may take up to 30 years to achieve its full flowering.  Historically, the wood was used in construction and for making tools, and the flowers and foliage were used to make foods, flavorings and teas.  We have just one tree, over 50 feet in height, in the mountain area, ZZE.  According to Arboretum records, it was planted in 1960.

Magnolia x soulangeana is the most widely planted magnolia in the Seattle area.  Despite its commonness, I treasure the lush beauty of its spring flowers and the striking architecture of its branches.  And I’m in awe of how long this remarkable genus, Magnolia, has survived on our planet.

Corinne Kennedy is a Garden Guide, frequent contributor to the Seattle Japanese Garden blog, and retired garden designer.