Repotting guide

When & how to repot Choy Sum 'Green Lance' (Brassica rapa var. parachinensis 'Green Lance')

Also called Green Lance choy sum, Chinese flowering cabbage.

More about choy sum 'green lance'

About Choy Sum 'Green Lance'

Brassica rapa var. parachinensis 'Green Lance' · also called Green Lance choy sum, Chinese flowering cabbage · edible

Choy Sum 'Green Lance' is a fast Chinese flowering cabbage grown for sweet, tender flowering stems, leaves, and small yellow buds harvested before full bloom. Quick to mature in 35-50 days, it crops productively in cool seasons and tolerates some heat, regrowing side shoots after the main stem is cut for repeated stir-fry harvests.

Mature size: 25-40 cm tall and 15-25 cm wide at harvest.

Watch for — Clubroot: Distorted, swollen roots and wilting in infected brassica soils. Rotate crops, lime to near-neutral pH, and improve drainage.

How to tell choy sum 'green lance' needs repotting

Repotting on a calendar is less reliable than reading the plant. For choy sum 'green lance', 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 choy sum 'green lance' 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 choy sum 'green lance'

Pot on seedlings as they grow; not a perennial repot. Choy Sum 'Green Lance'is grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Upright, loosely branching plant producing a central flowering stem with green leaves and yellow buds; cutting the main stem stimulates tender side shoots..

What size pot to step choy sum 'green lance' up to

Pot choy sum 'green lance' 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 choy sum 'green lance'

Pot choy sum 'green lance' 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 choy sum 'green lance'

Pot on before it is root-bound. Check choy sum 'green lance' 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, free-draining 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 choy sum 'green lance' 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 choy sum 'green lance'

Choy Sum 'Green Lance' wants rich, free-draining loam. Fertile, organic-rich, well-drained soil, pH 6.0-7.5. Lime acidic soils toward neutral to deter clubroot. Suits deep containers with nutrient-rich potting mix. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting choy sum 'green lance' — frequently asked questions

How often should you repot choy sum 'green lance'?

Pot on seedlings as they grow; not a perennial repot for choy sum 'green lance'. Choy Sum 'Green Lance' is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into rich, free-draining 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 choy sum 'green lance' need?

When is the best time of year to repot choy sum 'green lance'?

Can you put choy sum 'green lance' straight into a much bigger pot?

No. Even a fast-growing choy sum 'green lance' 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 choy sum 'green lance' after repotting?

Not immediately. Wait about 1 week after repotting choy sum 'green lance'. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.