Jooni

An exemplary photo of a Serissa bonsai

Serissa

2 Species

Species

Serissa foetida Serissa japonica

Serissa (Serissa japonica, also sold as Serissa foetida), also called snow rose or tree of a thousand stars, is a small evergreen shrub from East and Southeast Asia. A Serissa bonsai is loved for its tiny leaves, gnarled pale bark and masses of small white star-shaped flowers that can appear from spring into autumn.

In temperate climates it is grown indoors in a very bright spot, with an optional summer outside in light shade. Although it is often sold as a beginner tree, Serissa is temperamental: it reacts to being moved and to changes in temperature or watering by dropping leaves, so it suits patient beginners who can give it a stable spot.

At a glance Serissa japonica

Difficulty
Intermediate
Placement
Indoors
Light
Sun to partial shade
Watering
Moderate
Min. temperature
10°C (50°F)
Foliage
Evergreen

Fertilizing

Feed every two weeks with a balanced liquid fertilizer during the growing season, from spring to autumn. In winter, feed only once a month, and only if the tree is still growing in a warm room.

  • Water the tree before feeding so the fertilizer does not burn dry roots.
  • Do not feed a sick or freshly repotted tree; wait about a month after repotting.
  • A fertilizer for acid-loving plants used now and then helps if your water is hard.

Placement

Serissa needs a lot of light and reacts badly to being moved. Indoors, give it the sunniest window you have, where it gets some direct morning or late-afternoon sun, but shield it from harsh midday sun in summer.

  • Keep it at a stable 10–25°C (50–77°F) and never below 10°C (50°F).
  • Avoid radiators, air conditioners and drafty windows, since sudden temperature changes cause leaf drop.
  • In summer it can go outdoors in a bright spot with light shade at midday, sheltered from strong wind and heavy rain; move it in one step and leave it there.

Pruning

Do structural pruning in spring, as vigorous growth begins. During the growing season, let shoots grow four to five leaves and cut them back to two.

  • Trim right after a flush of flowers fades, not while buds are forming, so you do not cut off the next flowers.
  • Leave some foliage on every branch and remove only a little at a time.
  • The bark is thin, so wire carefully and check often; young branches bend easily.

Repotting

Repot every 2 years in spring; older trees can wait 3 years. Use a well-draining bonsai mix that holds some moisture, such as akadama with some pumice, and a slightly acidic pH.

  • Trim no more than about a third of the roots; cut roots give off an unpleasant smell, which is normal.
  • Use a pot of the same size, or slightly larger for a tree still in development, with mesh over the drainage holes.
  • Keep the soil evenly moist and out of strong sun for a few weeks, and wait a month before feeding.

Watering

Keep the soil evenly moist but never waterlogged. Check the top of the soil daily and water thoroughly when it feels dry to the touch, until water runs from the drainage holes.

  • Never let the pot stand in water, and never let the rootball dry out completely.
  • Water less in winter, when growth slows, but keep the soil slightly moist.
  • Use rainwater or soft water if you can; letting tap water stand overnight removes chlorine but not lime.

Seasonal care

  • Spring: Repot every two years and do structural pruning as vigorous growth begins. Resume feeding every two weeks, but wait a month after repotting.
  • Summer: Once nights are reliably warm, the tree can go outside into a bright spot with light shade at midday, sheltered from strong wind and rain. Keep the soil evenly moist and trim shoots after each flush of flowers fades.
  • Autumn: Bring it indoors before nights drop towards 10°C (50°F), in one move to the sunniest spot it can stay in all winter. Keep feeding every two weeks until growth slows.
  • Winter: Keep it at a stable 10–25°C (50–77°F), never below 10°C (50°F), as bright as possible and away from radiators, air conditioners and drafty windows. Water less often and feed only once a month if it is still growing.

Common problems

Serissa is quick to show stress, so most problems can be traced back to a recent change.

  • Sudden leaf drop: The classic Serissa reaction to being moved, low light, cold drafts, temperature swings or a change in watering. Choose one bright, stable spot, avoid moving the tree and correct watering gradually; it usually recovers within a few weeks.
  • Yellowing leaves and root rot: Waterlogged soil or a pot standing in water suffocates the fine roots. Keep the soil moist but never soggy, empty saucers and use a well-draining bonsai mix.
  • Aphids, spider mites and scale: Aphids gather on soft shoots, while spider mites and scale thrive in warm, dry indoor air. Rinse the foliage, raise humidity and treat with insecticidal soap or horticultural oil.
  • Unpleasant smell when pruning: Cut roots and branches give off a foul odor, which is why the plant is also called foetida. This is normal and not a sign of disease.
  • Few or no flowers: Usually caused by too little light or trimming off developing buds. Give the brightest spot available and prune right after flowering rather than before.