Chinese elm is a fast growing, deciduous or evergreen depending on its location. It forms a graceful, upright, rounded canopy with shiny, dark green leathery leaves. Elm is moderately salt tolerant. Several dwarf varieties, sports of Ulmus parvifolia, exist which grow slower than the ordinary Chinese elm but it produces a much finer network of twigs and branches. It is these sports which are used for bonsai.
Lighting: Will grow in full sun to partial shade.
Temperature: Zones 5B – 10A. More restricted zones may apply to some of the dwarf varieties.
Watering: Needs higher volumes of water
Fertilizing: To retain and produce small leaves, do not feed high nitrogen fast-acting fertilizers. Feeding three times a year is sufficient to maintain good color and healthy growth without enlarging the size of the leaves.
Pruning & Wiring: Most shaping can be done by pruning. The bark is thin and may be damaged easily.
Propagation: Because these dwarf varieties are sports of another plant, they can only be propagated by cuttings or layering. Cuttings may be made from new tip growth taken in early summer.
Repotting: They transplant well. Any type of soil with good drainage works well. They have heavy root growth so much have root room.
Pests & Diseases: Borers and chewing insects seems to be the only pests that affect this plant. Cankers may develop on young trunks where the soil is excessively wet.
Some species suitable for bonsai:
Ulmus parvifolia, var ‘Catlin,’ is a sport of the common Chinese elm. It is partly evergreen in mild climate and evergreen in the south. Its leaves are a 1/4 to 3/4 inches long and are a shiny, dark green, lanceolate and small than zelkova. John Catlin, a landscape designer in California, found this sport on an Ulmus parvifolia in a nursey around 1953. Jim Barrett named it Catlin Elm to honor the man who found it and to separate it from the Chinese Elm.
Ulmus parvifolia, var ‘Drake,’ USDA Hardiness zone 7 to 9, has small, dark green leaves and sweeping upright branches which form a rounded crown and greater leaf retention being almost evergreen in California and Florida.
Ulmus parvifolia, var ‘Dynasty,’ has smooth, dark grey bark, smaller leaves, and is vase-shaped. Change to a red color in the fall in northern climates.
Ulmus parvifolia, var ‘Frosty,’ has a small (.75 inch long) white-margined leaf which may revert back to green.