Japanese Maples, Fall Fireworks

Mary Robson (Ret.) Area Extension Agent
Regional Garden Column July 28, 2002

Japanese Maples have been cultivated since the 1600's. Hundreds of named cultivars have been bred, propagated and sold to eager gardeners. Even the taller upright varieties rarely grow to more than 25' in 50 years. They fit in even the smallest gardens. Given a well drained soil mix they live happily in deck or patio containers with otherwise minimal care. Whether container grown or planted in the landscape, maintaining consistent soil moisture is the key. Soggy poorly drained soil can be fatal.

Japanese Maples are not greedy and most will grow well in our area with little or no fertilizer. Over fertilized plants may lack the very characteristics they were grown for. For example variegated cultivars where the leaves will "revert" to a solid green. Then return to the variegated form when less nitrogen is available.

Pruning is another case where less is more. Major pruning should be done during the winter when the tree is dormant. Minor corrective pruning and training can be done almost any time. My particular pet peeve is the lace-leaf varieties pruned into umbrella shapes. They look like dumpy dowagers in hoop-skirts. The twiggy inner growth should be removed since it may invite insect and disease problems by holding soggy leaves next to healthy bark. More importantly much of the beauty of these plants is in the graceful curves of the trunk and limbs. I like to see the branches pruned so that the natural structure is enhanced and revealed. A well shaped lace leaf maple is as beautiful in winter as it is clothed in leaves the rest of the year. Think Salome and the Dance of the Seven Veils as you catch tantalizing glimpses of sinuous limbs through the cascading leaves.

Some of my other favorites are:

• A. japonicum f. acontifolium or Fern Leaf maple. A splendid tree with striking maroon and white flowers in the spring, deep green foliage in the summer and spectacular fall color. It may reach a height of 15'.
• A. palmatum atropurpureum 'Oshio beni' a widely sold and popular deep red leafed cultivar. It's an upright growing tree with a spreading canopy. It may eventually reach 20-25' tall. The new growth is very bright in spring, becomes a bronze during the summer and bright scarlet in the fall.
• A. palmatum 'Sango kaku' The common name is Coral Bark maple. It's outstanding feature is the brilliant color of the bark, particularly the younger wood. It can get up to 20' feet. The summer leaf color is a pleasant green with a showy yellow gold fall color.
• A. palmatum 'Shishagashira' The common name is lion's head or lion's mane. It has a closely spaced crinkled leaves on the twigs. The fall color is a tawny gold that looks very much like a lions mane. To keep the growth shrubby and compact avoid over-fertilizing. Slow growing and compact it is suitable for smaller gardens.

• A. griseum or Paper Bark maple. A hardy tree that originated in China rather than Japan. The outer bark curls back to expose a smooth cinnamon color inner bark which provides winter interest as well as contrasting beautifully with the rich green summer foliage. It has brilliant red fall color that persists until late in the season.

Visit the Washington Park Arboretum in Seattle to see the largest collection of Acer palmatum in any public garden in the country. Grounds and trails are open daily from 7am to dusk. Drive gates are locked at dusk. Donald G. Graham Visitors Center open seven days a week from 10:00 am - 4:00 pm. For more information call 206-543-8800 or visit their website.

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