Forsythia

Fertilizing

Apply a specialized bonsai fertilizer every two weeks during the growing season (spring through autumn). After flowering, use a general-purpose fertilizer, then switch to a low-nitrogen feed towards late summer to promote next year's flower buds. Pause fertilization during flowering and immediately after repotting. This varying fertilizer schedule helps maintain vigorous growth while encouraging abundant blooming.

During winter dormancy, reduce fertilization frequency to once monthly. The balanced feeding schedule throughout the year ensures proper nutrient uptake for both vegetative growth and flower production.

Placement

Place your forsythia bonsai outdoors in full sun to partial shade, with at least 4-6 hours of direct sunlight daily for optimal flowering. While hardy down to -10°C (15°F), protect from extreme cold by moving to a sheltered location or coldframe during harsh winters. Consider adding a layer of mulch or peat around the pot for additional insulation.

Light conditions should be adjusted seasonally - provide some afternoon shade during peak summer heat to prevent leaf scorch. Though adaptable to various conditions, consistent placement is key for maintaining health and encouraging proper dormancy cycles.

Pruning

Prune branches hard after flowering to maintain shape and encourage new growth. Focus initial pruning on removing dead, damaged, or crossing branches. Continue maintenance pruning through mid-summer, but avoid heavy pruning once flower buds begin forming for next spring. Remove older branches that have already flowered to promote young, vigorous growth.

The flexible nature of forsythia branches makes them ideal for wiring and shaping. Apply aluminum wire carefully, matching wire thickness to branch diameter, and remove after a few months before it cuts into the bark. When wiring new shoots, wrap gently and monitor closely as branches thicken rapidly.

Repotting

Repot every 2-3 years in early spring following the flowering period. Use a well-draining soil mix combining organic matter (humus, peat moss, or pine bark) with inorganic components (akadama, lava grit) maintaining a slightly acidic to neutral pH (5-7). The repotting process provides an opportunity to prune the root ball, encouraging better branching and maintaining the tree's compact form.

When repotting, avoid excessive root pruning - trim conservatively to maintain tree health. Choose a pot slightly larger than the previous one to accommodate growth while maintaining proper proportion to the tree's size.

Watering

Water thoroughly when the top layer of soil begins to dry, maintaining consistent moisture without waterlogging. This is particularly crucial during autumn when next year's buds are forming. Check soil moisture daily by inserting your finger about an inch deep - if it feels dry, water until it drains freely from the bottom.

Adjust watering frequency based on weather conditions and season. During active growth periods, water more frequently, while reducing frequency during winter dormancy. Remember that while forsythia bonsai are relatively drought-tolerant, consistent moisture is key for maintaining health and promoting strong flowering.

References

Hobby Gardeners - Forsythia Bonsai Care Guide Miyagi Bonsai - Forsythia Care Guide Green Zen Bonsai - Forsythia Guide