Repotting guide
When & how to repot Duku (Lansium domesticum)
Also called Langsat, Longkong, Duku Langsat.
More about duku
About Duku
Lansium domesticum · also called Langsat, Longkong · edible
Duku is a prized Southeast Asian fruit tree producing clusters of pale yellow, grape-like fruits with translucent sweet flesh and a mild, tangy flavour. It requires humid tropical conditions and a distinct dry season to trigger flowering. A slow-growing, long-lived tree that demands patience but rewards with delicious harvests. Toxicity to pets is not established; treat with caution.
Mature size: 10–30 m in native habitat; 2–4 m in container or managed tropical garden
Watch for — Root rot: Occurs in poorly drained or waterlogged soils; improve drainage and avoid overwatering.
How to tell duku needs repotting
Repotting on a calendar is less reliable than reading the plant. For duku, watch for these signs:
- Roots circling the bottom of the module or pot, or poking out of the drainage holes.
- The seedling dries out within a day and growth has visibly stalled.
- Roots are white and matted in a tight spiral when you tip the plant out.
- It has outgrown its current container for the stage of the season — pot duku on before it becomes hard root-bound.
For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.
How often to repot duku
Pot on seedlings as they grow; not a perennial repot. Dukuis grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Slow-growing evergreen tree with a spreading crown.
What size pot to step duku up to
Pot duku on gradually — a seedling jumped straight into a huge pot sits in cold, wet, airless soil and stalls. Step up one or two sizes at a time as the roots fill each container, finishing in a large final pot or the ground. The aim is roots that never circle and never check.
Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.
The best time of year to repot duku
Pot duku on through the active growing season, whenever roots fill the current container — there is no single date, just "before it becomes root-bound". Avoid potting on during a cold snap.
Step-by-step: repotting duku
- Pot on before it is root-bound. Check duku regularly; move it up as soon as roots reach the edge of the cell or pot, not after they have circled.
- Step up one or two sizes. Choose the next container up — not a giant one. Cold, wet, unused soil around a small root system stalls seedlings.
- Knock it out gently. Support the stem, tip the pot, and ease the rootball out without breaking it. A little teasing of circled roots at the base is fine.
- Pot into rich mix. Set it into fresh rich, well-drained, slightly acidic clay loam or loam; ph 5.5–6.5 at the same depth (tomatoes are the exception — they can go deeper to root along the stem).
- Water in and grow on. Water well, keep it in good light, and resume feeding once it is established and growing again.
Aftercare
Water duku in well and keep it in bright light; a freshly potted-on seedling can wilt for a day while roots settle, so do not overcompensate by drowning it. Do not fertilise for about 1 week — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.
The right soil mix for duku
Duku wants rich, well-drained, slightly acidic clay loam or loam; ph 5.5–6.5. Deep, fertile, moisture-retentive but well-drained soil is ideal. Amend with generous compost. Does not tolerate alkaline soils or waterlogging. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.
Repotting duku — frequently asked questions
How often should you repot duku?
Pot on seedlings as they grow; not a perennial repot for duku. Duku is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into rich, well-drained, slightly acidic clay loam or loam; ph 5.5–6.5 so the roots never circle the cell, ending in a large final container. A root-bound transplant stalls and never fully recovers.
What size pot does duku need?
Pot duku on gradually — a seedling jumped straight into a huge pot sits in cold, wet, airless soil and stalls. Step up one or two sizes at a time as the roots fill each container, finishing in a large final pot or the ground. The aim is roots that never circle and never check. Use our pot size calculator to size it from the plant's current pot and root spread.
When is the best time of year to repot duku?
Pot duku on through the active growing season, whenever roots fill the current container — there is no single date, just "before it becomes root-bound". Avoid potting on during a cold snap.
Can you put duku straight into a much bigger pot?
No. Even a fast-growing duku should only go up one pot size at a time. A vastly oversized pot holds a reservoir of wet soil the roots cannot reach, which stays cold and soggy and rots the roots — the opposite of what you wanted.
Should you fertilise duku after repotting?
Not immediately. Wait about 1 week after repotting duku. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.
Related guides
- Duku care — light, water, soil and common problems
- How often to water duku — the watering brief
- How to repot a plant — the complete step-by-step method
- Root-bound plant — how to spot and fix it
- Pot size calculator — size the next pot correctly
- When & how to repot black mission fig
- When & how to repot plantain
- When & how to repot lady finger banana
- All 11687 repotting guides in the Growli library