What Kind of Soil Do Chinese Elm Bonsai Need?

The Chinese elm can grow as a decidous or semi-evergreen bonsai.

The Chinese elm is a fast-growing, adaptable tree that thrives best in loamy, well-drained soil. A tolerant tree, the Chinese elm responds well to all levels of sunlight, from full sun to partial shade. It is highly drought tolerant and adapts to its climate by being deciduous or semi-evergreen. As a bonsai, the Chinese elm requires the same loamy, well-drained environment that has the ability to retain water and nutrients without promoting saturation and rot.

Soil Requirements

The Chinese elm bonsai is a highly drought-tolerant tree that responds poorly to saturated soils and wet feet. Long periods of saturation cause this elm bonsai to develop canker and root rot diseases, which result in progressive dieback and growth stunt. To ensure the Chinese elm’s healthy development, this bonsai’s soil must be fast draining and promote good air circulation for the root system.

Composition

The ideal soil for the Chinese elm bonsai is actually soil free. General potting soil can harden and limit the airflow through the soil. This limited aeration reduces the development of the Chinese elm bonsai’s fine root system. The ideal bonsai soil for this tree consists of a combination of inert aggregates and organic material. The aggregate materials can rocks, gravel or sand -- or a combination of the three -- while the organic materials consist of naturally decomposing materials such as pine bark or leaf mulch. In general, the aggregate material makes up about 60 to 75 percent of the bonsai soil, and the organic materials account for 25 to 40 percent.

Nutrients

The ideal soil mixture of aggregate and organic materials results in a relatively nutrient-free soil environment with a neutral pH balance. This nutrient-void material allows you to control the soil environment’s nutrient levels with proper fertilization. The Chinese elm bonsai requires regular fertilization applications throughout the growing season, from early spring through mid-fall. It requires higher levels of nitrogen feed during the spring, with slightly lower levels throughout the rest of the growing season. For instance, choose a 10-10-10 fertilizer during the spring, with an 8-8-8 combination during the rest of the year.

Irrigation

The Chinese elm bonsai cannot benefit from the ideal soil mixture unless it is properly watered. As a drought-tolerant bonsai, the Chinese elm requires deep and infrequent irrigation. This bonsai should be watered at soil level with tepid water until the excess water runs evenly from the container’s drainage holes. Once it is deeply irrigated, the Chinese elm’s soil should be allowed to dry slightly before the next irrigation. Rather than watering the Chinese elm bonsai on a schedule, water the bonsai only when the soil begins to feel dry. This will prevent overwatering and reduce the potential for infectious diseases and root rot.

References

• Bonsai4me: Ulmus Species/Elms
• University of Florida IFAS Extension: Ulmus Parvifolia -- Chinese Elm
• Bonsai Learning Center: Guidelines for Creating Bonsai Soil
• New England Bonsai Gardens: Chinese Elm Bonsai