Zelkova Serrata, A Replacement For American Elm

Zelkova is often listed as a replacement for American Elm since it has roughly the same vase shape and grows 90 to 100 feet tall with a 60 to 80- foot spread. But no tree will truly match the grace and elegance of the American elm. Zelkova is massive, with the trunk capable of growing to four feet or more in diameter. It has a moderate growth rate and likes a sunny exposure. Branches are more numerous and smaller in diameter than American Elm.

Scientific name: Zelkova serrata
Pronunciation: zell-KOE-vuh sair-AY-tuh
Common name(s): Japanese Zelkova, Saw-Leaf Zelkova
Family: Ulmaceae
USDA hardiness zones: 5 through 8
Origin: not native to North America

Height: 55 to 80 feet
Spread: 50 to 75 feet
Crown shape: vase shape
Crown density: moderate
Growth rate: medium
Texture: fine

Uses: Bonsai; large parking lot islands; wide tree lawns; medium-sized parking lot islands; medium-sized tree lawns; recommended for buffer strips around parking lots or for median strip plantings in the highway; shade tree; sidewalk cutout; residential street tree; tree has been successfully grown in urban areas where air pollution, poor drainage, compacted soil, and drought are common.

Leaf arrangement: alternate
Leaf type: simple
Leaf margin: serrate
Leaf shape: oblong; ovate
Leaf venation: pinnate
Leaf type and persistence: deciduous
Leaf blade length: less than 2 inches
Leaf color: green
Fall color: copper; orange; red; yellow
Fall characteristic: showy

Trunk/bark/branches: grow mostly upright and will not droop; showy trunk; should be grown with a single leader; no thorns
Pruning requirement: requires pruning to develop strong structure
Breakage: susceptible to breakage either at the crotch due to poor collar formation, or the wood itself is weak and tends to break
Current year twig color: brown Current year twig thickness: thin

Zelkova serrata forms heavy, spreading but mostly erect branches so keeping the leader intact and maintaining a clear trunk (6' to 8')is about all you need to do. Z. carpinifolia especially needs training to form the head as high as you can reach and pruning limbs off the lower trunk.

Unfortunately, the branches on Zelkova are often clumped together on the trunk at one point (head). Double and multiple trunks or leaders with embedded bark are also common. This is not a desirable form for planting in urban areas and needs to be prevented, or corrected, on existing trees. Purchase trees with branches spaced along the trunk so they can develop a secure hold onto the trunk. These will be hard to find but insist on it! Be sure that branches remain less than about half the diameter of the trunk to maintain a strong, durable form. Encourage nurserymen to grow trees with good trunk and branch structure.

The tree will tolerate most soil types, including those with a pH to about 7.5, but prefers a moist deep loam. It is reportedly risky to transplant in the fall. Established trees are fairly drought-tolerant, requiring little irrigation unless located in sandy soil. It makes a wonderful street tree even in restricted-soil tree pits, and is almost pest free. The crowns will eventually grow together if trees are planted on 30-foot-centers, forming a wonderful shaded street. This is a tough, urban tree which is often planted along streets in downtown and residential areas.

Cultivars include: ‘Green Vase’ somewhat resembles the vase shape of American Elms, is more upright in habit and tolerant of pollution, makes a great city street tree and produces a taller and narrower tree than ‘Village Green;’ ‘Village Green’ also resembles the shape of the American Elm and is more winter hardy than ‘Green Vase’, and may have a straighter trunk.