Serissa japonica 'Kowloon'

Common Name: snowrose 
Type: Broadleaf evergreen
Family: Rubiaceae
Zone: 7 to 9
Height: 2.00 to 4.00 feet
Spread: 3.00 to 5.00 feet
Bloom Time: April to September
Bloom Description: White
Sun: Part shade
Water: Medium
Maintenance: Medium
Suggested Use: Hedge
Flower: Showy
Leaf: Colorful, Evergreen
Other: Winter Interest

Culture

Winter hardy to USDA Zones 7-9, but possibly Zone 6 if sited in a protected location and mulched. Grow in consistently moist, moderately fertile, well-drained soils in part shade (best with morning sun and afternoon shade). Avoid overly moist soils and drought. This shrub dislikes varied growing conditions. It may drop its leaves if soils dry out too much, at which point watering should be significantly reduced to avoid the possible development of root rot. Deadhead flowers after bloom to extend the bloom period. Prune after flowering is completed to maintain dense form.

This shrub only remains evergreen in frost-free winter climates (Zones 9b-11). It will not retain foliage in colder locations where it typically begins losing leaves in autumn as soon as temperatures drop below 40 degrees F. Branches usually die to the ground when temperatures dip into the low 20's F. as the plant begins to take on the habit of an herbaceous perennial rather than evergreen shrub.

This is a popular bonsai plant (especially in Japan). It will usually thrive when placed in a location featuring stable year-round growing conditions (adequate sun, little temperature fluctuation, consistent and even moisture and no relocation to other sites in the home). But as a bonsai plant, it is considered to be very temperamental in large part because it tends to drop leaves if roots get too moist or too dry or if temperatures get too hot or too cold, or if the growing environment is significantly changed.

Best propagated from cuttings which usually root easily.

Noteworthy Characteristics

Serissa japonica, commonly known as snowbush, snowrose or tree of a thousand stars, is a small, stiffly-branched, evergreen to semi-evergreen to deciduous shrub that typically grows to 2-4’ tall with a slightly wider spread. It is native to moist open woodlands, wet meadows, streambanks and forested slopes in subtropical areas of India, China and Japan. This genus has only one species, namely S. japonica, which was formerly known as S. foetida (now a synonym). This shrub is grown for its dense foliage, rough gray bark and long spring to fall bloom of star-shaped white flowers.

Branching wiry stems form a bushy dome. Stems are clad with tiny, opposite, densely crowded, somewhat leathery, pointed, ovate, deep green leaves (to 1/4 to 1/2” long). Leaves emit a fetid smell when bruised or crushed as described by the prior specific epithet of foetida. Funnel-shaped, star-like, white flowers (to 1/3” across) emerge from pink buds in a long spring to fall bloom. Flowers have tubular bases and 4-6 spreading petal-like lobes. Flowers appear singly or in clusters from the leaf axils and branch ends, often covering the entire shrub with bloom as suggested by the sometimes used common name of tree of a thousand stars.

Genus name is derived from the name used in India for this shrub.

Specific epithet of japonica is in reference to its Japanese native territory.

‘Kowloon’ is a variegated cultivar that features green leaves with pale yellow margins which cover 1/ 3 to 1/ 2 of the leaf surface. Foliage appearance has given rise to the common name of yellow-rim for this plant.

Problems

No serious insect or disease problems.

Garden Uses

Compact hedge. Border fronts. Foundations. Path edgings. Containers. Popular bonsai subject (gnarled trunk, evergreen leaves and frequent bloom).