Japanese Zelkova or Zelkova

(Ulmaceae - Elm Family)

Form

• large shade tree
• maturing at about 60' tall by 60' wide
• upright vased growth habit
• rapid growth rate in youth, slowing to a medium growth rate during middle age and at maturity

Culture

• full sun to partial sun
• prefers moist, well-drained, deep soils in full sun, but is very adaptable and urban tolerant (especially to heat, drought, pollution, poor soils, and soils of various pH)
• propagated by seeds, rooted stem cuttings, and grafting cultivars onto seedling rootstock
• Elm Family, with no disease or pest problems of significance, including resistance to Dutch Elm Disease
• commonly available in ball and burlap form
• may be the best replacement for the American Elm (Ulmus americana), in terms of Japanese Zelkova's resistance to Dutch Elm Disease and its vased growth habit (although it is not nearly as tall or arching as American Elm)
• due to its very dense canopy when young, it should be periodically thinned to allow light flow into the interior canopy and to reduce the number of branches originating at the vase branch point
• Japanese Zelkova is very sensitive to being transplanted in Autumn, and care should be taken to amend the soil, fertilize, water thoroughly, mulch adequately, and avoid Winter salt spray, to enhance survival chances during the first Winter, if transplanting cannot be delayed until Spring

Foliage

• alternate, ovate, serrated to crenate margins, with a short acuminate tip and a base that is equal on both sides of the petiole
• dark green and clean Summer foliage transitions to a very appealing mixture of yellow, gold, orange, burgandy, red, and wine fall color, in October and early November

Flowers

• monoecious and ornamentally insignificant, in April

Fruits

• ornamentally insignificant drupes ripen in October, being hidden by the foliage

Twigs

• thin, fine-textured, reddish-brown to gray-brown, slightly pubescent, and zig-zag, having buds that diverge at wide angles from the stems
• twigs and small branchlets usually grow within a single plane for an entire young branch, gradually becoming three-dimensional in their branching as the limb matures

Trunk

• young bark is shining reddish-brown, relatively smooth, and with prominent horizontal lenticels, changing to medium gray or blue-gray branches that are also relatively smooth and lenticeled
• maturing as a slightly exfoliating, mottled combination of gray, peach, and orange ornamental bark on the larger branches and trunk
• ascending branches of young trees are usually much-branched at about 6 to 10 feet above the ground, with all of the major branches that diverge from the top of the basal trunk usually originating within 4' of each other to yield a sudden but graceful vased growth habit
• fortunately, the strong wood and semi-wide crotch angles are not prone to shearing off during heavy winds or ice loads

ID Summary

• strongly vased growth habit, with many fine-textured, zig-zag twigs having serrated, ovate, dark green leaves that have either a mixed or burgandy-wine fall color, with a rapid growth rate in youth and ornamental bark with age

USAGE

Function

• shade, specimen, or focal point tree

Texture

• medium-fine texture in foliage and when bare
• thick density in foliage and when bare

Assets

• graceful and stately vased growth habit above a straight basal trunk
• rapid growth and establishment
• excellent dark green and clean Summer foliage
• excellent fall color
• ornamental bark with age

Liabilities

• marginally hardy in severe zone 5 Winters
• branching can become so thick after about ten to fifteen years of rapid growth that some canopy thinning is necessary in youth

Habitat

• zones 5 to 8
• native to China

SELECTIONS

Alternates

• vase-shaped large shade trees (Ulmus americana 'Delaware', Ulmus parvifolia [in some cases]) or ornamental trees (Cornus kousa, Crataegus viridis 'Winter King', Prunus serrulata 'Kwanzan', etc.)
• shade trees with excellent fall color(Acer rubrum, Acer saccharum, Fraxinus americana, Nyssa sylvatica, Ulmus parvifolia, etc.)
• trees with ornamental bark (Acer griseum, Acer pensylvanicum, Betula nigra, Carya ovata, Fagus sylvatica, Ulmus parvifolia, etc.)

Variants

• Zelkova serrata 'Green Vase' - more upright-vased in growth habit with strongly ascending branches, rapidly growing, to 65' tall by 55' wide, with yellow-orange to bronze-red fall color
• Zelkova serrata 'Village Green' - more round-vased at maturity, to 45' tall by 40' wide, with wine-red fall color

NOTES

Translation

• Zelkova is the European name for another species of the genus.
• serrata translates as "saw-toothed" or "serrated", in reference to the leaf margins.

Purpose

• Japanese Zelkova is a large vase-shaped shade tree, with several other ornamental features (ornamental bark, clean Summer foliage, fall color, fine-textured twigs) that make it an excellent substitute for the American Elm.

Summary

• Zelkova serrata is one of the two best large shade trees with a vase shape, with a rapid growth rate and stately appearance that, coupled with its other ornamental features of Summer/Autumn foliage, fine texture, and attractive bark, make it a truly underutilized tree in modern landscapes.