Serissa japonica
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Zones 11 to 12, indoor. A small evergreen or semi-evergreen shrub from southern China and Taiwan, the native range Kew gives.
Rubiaceae (the coffee family) · Subtropical evergreen to semi-evergreen flowering shrub, kept as an indoor bonsai
Compare your tree against these to confirm the species and spot problems early.
| USDA zones | 11 to 12 in a pot: zone 12's winter lows of 50 to 60°F (10 to 16°C) stay above the bonsai floor of 45 to 50°F (7 to 10°C) [10] [11], zone 11's lows of 40 to 50°F (4 to 10°C) come close to it, so bring it in on colder nights there [15] [16]. In the ground NC State gives 7 to 11 [2] and UF/IFAS 7 to 9 [3] |
|---|---|
| Indoor / outdoor | Indoor: indoors from fall to spring [10], ideally all year per Yorkshire Bonsai [12]; outside in summer only while nights stay above 50°F (10°C) [10] |
| Light | Sources differ: a sunny, wind-protected place outside [10]; indoors bright but not too sunny, such as an east or west window [11]; as a garden shrub, partial sun to partial shade with morning sun [2] |
| Water | Keep the rootball moist without overwatering [10] [12] and never let it dry out completely [10]; Bonsai4Me waits until the compost has nearly dried [11]; it rots in waterlogged soil [6] |
| Soil | A standard bonsai mix [10]; Mistral uses pure akadama or akadama with 20% volcanic clay [13]; it must drain well [6] |
| Repot | Every 2 years [10] [13]; every 2 to 3 years [11] [12]; retailer Brussel's, in general indoor bonsai advice, every 4 to 5 years, only when pot-bound [14] |
| Frost | None: does not tolerate frost [10] [12]; Bonsai4Me protects it below about 45°F (7°C) [11] |
| Mature height | About 1.5 to 2 ft (45 to 60 cm) [9]; 1.6 to 3.3 ft (0.5 to 1 m) [6]; 2 to 4 ft in a garden [2] |
| Growth rate | Moderate: NParks' rating for the garden shrub [6]; the bonsai sources give no rating |
| Season of interest | Tiny white flowers from spring through summer [10]; NC State says spring to fall [2] |
| Leaf reduction | Not rated by the sources we checked; the leaves are small to begin with, 1/4 to 1/2 in [2] |
| Main risks | Main risks, not ranked by any source: watering errors (root rot or drying out) [10], change and moves [10] [11], cold [10], dry indoor air [11] |
Serissa is a small evergreen or semi-evergreen shrub [9] from southern China and Taiwan, the native range Kew gives [1]. Kew places it in the Rubiaceae [1], which NC State calls the coffee family [2]. Kew accepts the name Serissa japonica and treats Serissa foetida as a synonym [1]; Bonsai Empire notes that most people still use the old name Serissa foetida [10], and the RHS lists it as tree of a thousand stars with that synonym [8]. UF/IFAS and NParks also call it Japanese serissa [3] [6].
Wikipedia counts it among the bonsai most often sold in America and Europe [9], and NC State says it is valued for its gnarled trunk, glossy leaves and frequent flowers [2].
It is a fussy tree. Bonsai Empire says it is not easy to care for, suits experienced growers better, and reacts badly to changes in location and temperature [10]. Bonsai4Me calls it notoriously hard to keep, for skilled hobbyists and newcomers alike [11]. Wikipedia is milder: not difficult to maintain, but very fussy, dropping leaves when watered wrongly, kept too hot or cold, or moved [9].
Foliage. Small, leathery, glossy leaves in opposite pairs [2] [6], 1/4 to 1/2 in long per NC State [2], about 1/4 to 7/8 in (0.6 to 2.2 cm) per NParks [6]. Variegated forms have yellow [2] [3] or whitish margins [7]. Bruised leaves smell unpleasant [5] [9], as do cut bark and roots [11].
Bark & trunk. A gnarled trunk, one reason it is valued in bonsai [2].
Growth habit / form. A dense, dome-shaped shrub [2] that suckers from the base [3].
Flowers / fruit. White, star-shaped flowers about 1/3 in across with 4 to 6 petals [2]; about 3/8 in (1 cm) per NParks and Wikipedia [6] [9]. Pink buds turn white [9]; double-flowered cultivars exist [9]. The fruit is a drupe 0.08 to 0.12 in (2 to 3 mm) long [6].
Look-alikes & how to tell them apart: No source we checked names a look-alike. It is also called Japanese boxthorn [6] [9], so check the botanical name on a label. Tiny opposite leaves, white star flowers [2] and the smell of bruised leaves [5] [9] are typical of serissa.
In the ground. NC State gives USDA zones 7 to 11, noting it is not evergreen below 40°F (about 4°C) [2]; UF/IFAS in north Florida gives zones 7 to 9 [3]. These are garden figures, not bonsai figures. UF/IFAS rates it not a problem species in Florida [4]. The zones row gives zones 11 to 12 for a potted tree: USDA zones are bands of the average annual extreme minimum winter temperature, 10°F wide [15]; zone 11's band is 40 to 50°F and zone 12's is 50 to 60°F [16], the only ones that meet or come near the bonsai sources' floor below.
In a pot. The bonsai sources want it much warmer:
Keep conditions stable: avoid needless moves [10], which stress the tree until it settles [11].
The sources differ. Bonsai Empire wants a sunny, wind-protected place outside in the growing season; indoors, the warmer the spot, the more light it needs, and grow lights help [10]. Bonsai4Me prefers a bright but not too sunny permanent spot, such as an east or west windowsill [11]. Brussel's gives outdoor trees morning sun and afternoon shade [14], as NC State does for the garden shrub [2]. Pick one spot and leave the tree there [10] [11].
Evenly moist, never soggy, never bone dry. Keep the rootball moist without overwatering, and never let it dry out completely [10] [12]. Bonsai4Me waits until the compost has nearly dried before watering again [11]. It rots in waterlogged soil, and too much or too little water, or low humidity, can yellow the leaves and make them drop [6]; Mistral also links excess water to leaf drop [13].
Bonsai Empire avoids very calcareous water and mists the foliage with lime-free water when the tree is not in flower [10]. Bonsai4Me stands the pot on a gravel tray kept wet, never in water [11]. If leaves drop after a change, water a little less [10]. The University of North Florida says the garden shrub tolerates drought [5]; no bonsai source says that of a potted serissa.
Bonsai Empire uses a standard soil mix [10]; Mistral uses pure akadama, or akadama with 20% volcanic clay [13]. Good drainage matters [6].
Repotting intervals vary: every 2 years [10] [13], 2 to 3 years [11] [12], or 4 to 5 years, only when pot-bound, in retailer Brussel's general indoor bonsai advice [14]. Bonsai4Me and Mistral repot in spring [11] [13]. It dislikes root pruning [11], so cut the roots only moderately [10]; they smell bad when cut [10] [13].
The sources differ on timing:
Feeding matters most during the long flowering period [9]. Do not feed a tree that has dropped its leaves or is not growing [10] [11].
Serissa takes hard pruning, in early spring for Bonsai Empire [10], at any time of year for Mistral [13]. It buds back even on old wood [13] and branches densely from old and new wood [7] [11].
Wiring. Bonsai Empire wires at any time, with great care because the branches are delicate, and removes the wire after about six months [10]; Mistral wires in spring [13].
Styles. All forms except formal upright, in extra-small to medium sizes [11].
Ease: Bonsai Empire says it propagates easily from semi-hardwood cuttings [10]. Best methods: cuttings [6] [10] [11].
Bonsai4Me takes softwood cuttings in spring or early summer and semi-ripe cuttings in late summer, with bottom heat to help rooting [11]. NC State recommends root cuttings [2].
Aphids, root aphids and spider mites; use a suitable pesticide and raise the humidity [10] [12]. Scale insects [7] [11]. NC State adds woolly aphids on the garden shrub [2].
Root rot. From overwatering or poor soil [10]; it rots in waterlogged soil [6]. Treat by repotting into fresh soil after removing damaged roots [10].
Mildew. Listed by NC State [2].
Yellowing and leaf drop. Usually caused by placement, low humidity or watering [11], not disease. UF/IFAS reports no serious disease on the garden shrub unless it is overfed or overwatered [3].
No source we checked ranks these. They are the main risks the sources describe, in no particular order:
Trees from our own bench, filmed while we worked on them.
Play video (0:29)I cut this variegated serissa back hard in one session. The hard cut looks alarming, and it is not the part that matters: serissa back-buds readily, even on old wood. What actually kills serissa is watering. It wants moist but well-drained soil, and it dies from both root rot and drying out completely.
