Chapter 136 Zelkova serrata
136.2 Soil: General Deciduous / Rich Conifer Mix
Ratio: 3 parts bark, 1 part grit
Add-ins: dolomitic limestone (~5 lbs/yd), Tree-Tone (15 lbs/yd)
pH: ~6.5 (slightly below neutral)
Moisture: Average. This tree prefers moist, well-drained soils.
136.3 Light
Routine: full to partial sun.
Summer: Mid-day shade is helpful but not essential.
It is adaptable and tolerant of heat, little water, nutrient-poor soils and various pH. It should be periodically thinned to allow light into the inner canopy. Zelkova is propagated by seeds, that germinate without pretreatment, though the percentage is better when stratified at 5 °C (41 °F) for 60 days.
136.4 Cultivation Notes
Zelkova serrata is a medium-sized deciduous tree usually growing to 30 m (98 ft) tall. It is characterized by a short trunk dividing into many upright and erect spreading stems forming a broad, round-topped head. The tree grows rapidly when young though the growth rate slows to medium upon middle age and maturity.
Fall leaf color ranges from brown/copper or golden yellow to orange, red, or burgundy.
136.4.1 Potting & Root Pruning
Repot in early spring.
136.4.1.1 Top & Branch Management
Zelkova has very hard wood. Keep this in mind when pruning branches.
Heavy pruning: remove branches in spring.
Fine pruning: prune extension growth in summer as needed. Leave 1-2 pairs of leaves when pruning.
Leaf pruning: can be leaf pruned in summer.
136.4.2 Feeding
Zelkova likes a fertilizer richer in potassium and nitrogen which encourages new vegetation and floral buds. Do not use liquid feed in late fall or early spring. Liquid fertilizers encourage tender growth that can be damaged by early freezes in fall and late freezes in spring.
136.4.3 Pests & Problems
The threats to this tree include colder windy conditions, which often result in twig dieback. It is highly resistant to Dutch elm disease, which makes it a good replacement tree for American elm. Zelkova serrata also shows good resistance to elm leaf beetle and Japanese beetle.
Chemical Warnings
136.4.4 Winter Storage
Store in mulch outdoors. Try to place in a shaded area so buds do not break in a mid-winter warm spell. Protect from wind.
136.5 Propagation Notes
A large, well-developed zelkova in the National Arboretum collection. Link to original image.
Because germination requires stratification, the seed is best sown early in the year. To ensure survival it may be necessary to pot the tree and grow it in a greenhouse for its first winter. It may be reintroduced into its permanent habitat after the final frost.
136.6 Artistic & Styling Notes
A Japanese zelkova in the National Arboretum collection, starting to develop its autumn colors. This tree has been in training for over 100 years. Link to original image.
Zelkovas are particularly well suited for broom styles.
136.7 Additional Information
136.7.1 Natural History
Zelkova is a group of 6 species that are native to southern Europe, and southwest and eastern Asia. Zelkova serrata or Japanese zelkova is found in Japan, Korea, Kuril Islands in Russia, Taiwan, and China. Zelkovas are similar to elms in their native habitats and growing conditions. However they are resistant to most elm diseases.