Japanese spiraea is a native of Southwest China and has spread over much of China, Korea and Japan. Its habitat is streams edges and other boggy areas. It prefers a full sun location but can tolerate shade. It is a deciduous shrub with clusters of rosy-pink flowers at the tips of the branches. It makes lovely small to medium Bonsai, full of year-round character.
The Japanese Spiraeas make lovely small to medium Clump style bonsai. They prefer a full sun location but can tolerate shade. It is best placed in a full sun position to enjoy a full blush of flowers and excellent autumn colour.
Watering: Water generously is a very thirsty plant but hates to be waterlogged for too long.
Feeding: Feed with balanced low availability fertiliser. Slow-release organic fertilisers are best suited to it. For example, if using a liquid feed every two weeks between March and Jun and then again between Aug and October.
Repotting: The Spirea prefer moist soil, so best to repot in a well-drained soil mix with good moisture retention abilities. I use two parts Akadama, one part Pumice and one part Sphagnum moss or Coconut Coir.
Pruning: Prune in Autumn after flowering has completed. Reduce or remove long runners and suckers. Deadhead flowers and remove all corymbs. It will encourage more delicate branching.
Wiring: Shaping usually is carried out with pruning, but if required, it is best to wire in Autumn, but be careful as branches are stiff and could snap easily.
Propagation: Spirea can be multiplied from Ground layering, Semi-hardwood and Hardwood cuttings. Semi-hardwood cutting between 10-15 cm long can be taken in Mid to late summer. Hardwood cuttings about pencil thick can be taken in Autumn. Use a rooting agent for best results.