Spiraea vanhouttei is a dense, deciduous shrub that typically matures to 8-10 tall and to 12-15 wide. It is native to China and Japan. This shrub features oval to obovate, sharply-toothed, glossy, dark green leaves (to 4 long) that turn attractive shades of yellow, orange and red in fall. Five-petaled, white flowers in flat-topped, terminal clusters (corymbs) bloom in June.
Related plant:
Spiraea Grefsheim
Related plant:
Spiraea Arguta
About soil condition, Spiraea vanhouttei prefers moist to wet conditions, and can tolerate short periods of drought. It grows best in rich, loamy soils, but will also do well in sandy or clay soils as long as they are well-drained. It is not particular about pH, and will grow in soils with a pH range of 4.5 to 7.5.
Similar to other shrubs in the Spiraea genus, the Vanhouttei spirea prefers full sun but will tolerate some shade. This deciduous shrub will also do well in average to poor soil as long as it is well-drained. As far as watering goes, the Vanhouttei spirea is drought resistant once established, but will appreciate occasional deep watering during prolonged periods of drought.
The temperature condition of Spiraea vanhouttei is that it should be kept in cool to cold conditions. It should be kept moist but not saturated. In the spring, it should be kept in cool conditions with high humidity. In the summer, it should be kept in a cool, shady place. In the fall and winter, it should be kept in cool to cold conditions with low humidity.
Ideal humidity condition for this plant is between 40 to 60%. The plant does not like to be in waterlogged or soggy soil, and will start to show signs of stress, such as wilting leaves, if the roots are constantly wet. If the air is too dry, the leaves will start to turn brown and drop off.
About fertilizer, this kind of plant need full sun and does best in moist, well-drained, slightly acidic soils. Add a general purpose fertilizer before new growth begins in spring. For optimal growth, fertilizer should be applied monthly during the growing season. As far as the roots go, they are fibrous and spreading, so be sure to provide them plenty of room to grow when planting. If you're growing them in containers, make sure the pots are big enough. They're not overly fussy about soil, but do best in moist, well-drained, slightly acidic soils.
Pruning your spiraea vanhouttei (bridal wreath spirea) is an important part of keeping this beautiful shrub healthy and happy. You should prune it in late winter or early spring, before new growth begins. Cut back the plant by about one-third its overall size. This will encourage new growth and help keep the plant from getting too leggy.
Propagation is by softwood cuttings taken in spring or early summer. The cuttings should be taken from young, healthy shoots that have not flowered. Cuttings should be about 10cm (4in) long and inserted into pots of moistened propagating sand. The pots should be placed in a cool propagator or sheltered spot outdoors and kept moist. Rooting should occur within 2-3 weeks. Once rooted, the young plants can be potted on and grown on in a cold greenhouse or outdoors in a sheltered spot.
Usually, the plant growth rate during the growing season is fast. They can grow 2 to 3 feet in a single season. Once they have reached their mature height, their growth slows down. They may only grow a few inches each year after that.
Common problems for this kind of plant are powdery mildew, leaf spots, and rust. These can all be controlled with fungicides. Spider mites can also be a problem, but they can be controlled with insecticides.
Source:
Vanhoutte Spirea (Spiraea x vanhouttei)-Hort Answers
Spiraea x vanhouttei habit: UIPLANTS - University of Illinois
Vanhoutte Spirea (Spiraea x vanhouttei) - Virginia Tech
