Repotting guide

When & how to repot Bok Choy 'Black Summer' (Brassica rapa var. chinensis 'Black Summer')

Also called Black Summer bok choy, dark bok choy.

More about bok choy 'black summer'

About Bok Choy 'Black Summer'

Brassica rapa var. chinensis 'Black Summer' · also called Black Summer bok choy, dark bok choy · edible

'Black Summer' is a fast, uniform bok choy with very dark green leaves and crisp pale stalks, bred for slow bolting and heat tolerance so it crops reliably through warmer weather. A cool-season Asian green, it matures in roughly six to eight weeks and is ideal for successional sowing in spring, summer, and autumn for stir-fries and steaming.

Mature size: About 20-30 cm (8-12 inches) tall and wide at harvest; baby leaves can be cut earlier.

Watch for — Bolting: Heat, long days, and root stress make plants run to flower prematurely. Use this heat-tolerant variety, sow in cooler windows, and keep moisture even.

How to tell bok choy 'black summer' needs repotting

Repotting on a calendar is less reliable than reading the plant. For bok choy 'black summer', 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 bok choy 'black summer' 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 bok choy 'black summer'

Pot on seedlings as they grow; not a perennial repot. Bok Choy 'Black Summer'is grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Upright, vase-shaped rosette of dark green blades on crisp white-green petioles; a biennial grown as an annual that bolts to a yellow flower stalk under stress or heat..

What size pot to step bok choy 'black summer' up to

Pot bok choy 'black summer' 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 bok choy 'black summer'

Pot bok choy 'black summer' 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 bok choy 'black summer'

Pot on before it is root-bound. Check bok choy 'black summer' 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 bok choy 'black summer' 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 bok choy 'black summer'

Bok Choy 'Black Summer' wants fertile, moisture-retentive loam. Rich in organic matter with good drainage and a near-neutral pH of 6.0-7.5. Work in compost before sowing; thin, dry soils encourage premature flowering. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting bok choy 'black summer' — frequently asked questions

How often should you repot bok choy 'black summer'?

Pot on seedlings as they grow; not a perennial repot for bok choy 'black summer'. Bok Choy 'Black Summer' 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 bok choy 'black summer' need?

When is the best time of year to repot bok choy 'black summer'?

Can you put bok choy 'black summer' straight into a much bigger pot?

No. Even a fast-growing bok choy 'black summer' 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 bok choy 'black summer' after repotting?

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