The Japanese Zelkova (Zelkova serrata), often called the Japanese gray-bark elm, is a highly prized species in bonsai due to its elegant, fine branches, smooth gray bark, and small, serrated leaves that turn vibrant shades of orange and yellow in autumn. With proper care, it can develop a graceful, natural appearance. This species is highly favored for broom style bonsai, (hokidachi), but is suitable for many other style as well.

General Care Overview:

• Light: Thrives in full sunlight, which encourages healthy growth and vibrant leaf color. Provide some shade in summer to avoid leaf scorch.

• Watering: Keep the soil consistently moist but avoid waterlogging. Never let the soil dry out completely.

• Soil: Use a well-draining bonsai soil mix, such as akadama.

• Fertilizer: Feed with a balanced bonsai fertilizer every 2-4 weeks during the growing season.

• Pruning: Regular pruning is necessary to maintain shape and promote fine branching.

• Repotting: Repot every 2-3 years in early spring, using fresh, well-draining soil.

Spring Care (March to May):

• Repotting: Repot the tree in early spring as buds begin to swell but before leaves emerge. Trim roots moderately and take care to expose the nebari (surface roots) slowly over time.

• Pruning: Perform structural pruning to shape the tree, remove crossing branches, and enhance ramification.

• Defoliation: If the tree is vigorous, you can perform partial defoliation later in spring, after leaves have hardened off, to encourage smaller leaves and finer branching.

• Wiring: Wire branches in early spring when they are more flexible, but monitor for wire marks as the tree grows. Wiring is best carried out in fall, as wire scarring on this species is practically permanent.

• Fertilizing: Begin fertilizing with a balanced or slightly nitrogen-rich fertilizer as new growth appears.

• Watering: Increase watering frequency as temperatures rise, keeping the soil moist but not waterlogged.

Summer Care (June to August):

• Sun Protection: Protect the tree from intense afternoon sunlight, particularly in hot climates, to prevent leaf scorch. Use partial shade or a mesh screen if necessary.

• Watering: Increase watering frequency during hot weather to prevent the soil from drying out.

• Pruning: Perform light pruning to maintain the tree’s shape and remove overly vigorous shoots.

• Pest Management: Watch for pests like aphids, spider mites, and scale, and treat infestations promptly with insecticidal soap or neem oil.

• Fertilizing: Continue feeding every 2-4 weeks with a balanced fertilizer, reducing the nitrogen content in mid to late summer to prepare the tree for autumn.

• Humidity: Mist the foliage occasionally during dry periods to maintain humidity levels and prevent leaf desiccation.

Autumn Care (September to November):

• Foliage Display: Enjoy the beautiful autumn colors as the leaves turn golden, orange, or red before dropping.

• Pruning: After leaf fall, perform structural pruning to refine the tree’s shape, remove unwanted branches, and enhance branch structure.

• Wiring: Autumn is an excellent time for wiring, as the risk of scarring is minimal. Take care to check the wire in the following spring before leaves emerge.

• Fertilizing: Stop fertilizing after leaf drop.

• Watering: Gradually reduce watering frequency as the tree’s growth slows, but do not let the soil dry out completely.

Winter Care (December to February):

• Dormancy: The Zelkova serrata is deciduous and requires a proper dormancy period. Place it in a protected outdoor location or cold frame where it can experience cool temperatures without being exposed to extreme frost.

• Frost Protection: Protect roots from freezing by wrapping the pot in insulating material or mulching around the container. In very cold climates, place the tree in an unheated garage or greenhouse.

• Watering: Water sparingly during dormancy, ensuring the soil remains slightly moist but not soggy.

• Pest and Disease Check: Inspect for overwintering pests or fungal issues and treat as necessary.

• No Pruning or Fertilizing: Avoid heavy work during winter, as the tree is not actively growing.