Repotting guide
When & how to repot Tatsoi (Brassica rapa var. narinosa)
Also called tatsoi, spinach mustard, rosette bok choy.
More about tatsoi
About Tatsoi
Brassica rapa var. narinosa · also called tatsoi, spinach mustard · edible
Tatsoi forms a low, flat rosette of spoon-shaped, glossy dark green leaves with a mild, mustardy-spinach flavour. One of the most cold-hardy Asian greens, it sweetens after frost and can crop into winter under cover. Quick from seed and excellent as baby leaf or full rosettes, it shines in salads, soups, and quick stir-fries.
Mature size: About 15-25 cm (6-10 inches) across and 10-20 cm (4-8 inches) tall; cut as baby leaf much smaller.
How to tell tatsoi needs repotting
Repotting on a calendar is less reliable than reading the plant. For tatsoi, 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 tatsoi 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 tatsoi
Pot on seedlings as they grow; not a perennial repot. Tatsoiis grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Low, flat rosette of spoon-shaped dark green leaves hugging the ground; a biennial grown as an annual that bolts upward to a flower stalk in heat or long days..
What size pot to step tatsoi up to
Pot tatsoi 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 tatsoi
Pot tatsoi 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 tatsoi
- Pot on before it is root-bound. Check tatsoi 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 fertile, moisture-retentive loam 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 tatsoi 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 tatsoi
Tatsoi wants fertile, moisture-retentive loam. Rich in organic matter with good drainage, pH 6.0-7.5. Compost-improved beds support its fast leafy growth; avoid waterlogging beneath the ground-hugging rosette. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.
Repotting tatsoi — frequently asked questions
How often should you repot tatsoi?
Pot on seedlings as they grow; not a perennial repot for tatsoi. Tatsoi is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into fertile, moisture-retentive loam 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 tatsoi need?
Pot tatsoi 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 tatsoi?
Pot tatsoi 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 tatsoi straight into a much bigger pot?
No. Even a fast-growing tatsoi 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 tatsoi after repotting?
Not immediately. Wait about 1 week after repotting tatsoi. 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
- Tatsoi care — light, water, soil and common problems
- How often to water tatsoi — 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 tomato
- When & how to repot pepper
- When & how to repot cucumber
- All 5561 repotting guides in the Growli library