Repotting guide

When & how to repot Mustard Greens 'Osaka Purple' (Brassica juncea 'Osaka Purple')

Also called Osaka Purple mustard, Japanese purple mustard.

More about mustard greens 'osaka purple'

About Mustard Greens 'Osaka Purple'

Brassica juncea 'Osaka Purple' · also called Osaka Purple mustard, Japanese purple mustard · edible

Mustard greens 'Osaka Purple' is a Japanese mustard with rounded, purple-tinged green leaves and a warm, garlicky-mustard heat that is mild as baby leaf and stronger when mature, cropping in about 40-50 days. Cold-tolerant and good for cut-and-come-again, it shines in autumn and spring. Cool conditions, rich soil and steady water keep its leaves tender.

Mature size: Leaves about 20-40 cm long; plant roughly 30-40 cm tall and 25-30 cm wide.

How to tell mustard greens 'osaka purple' needs repotting

Repotting on a calendar is less reliable than reading the plant. For mustard greens 'osaka purple', 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 mustard greens 'osaka purple' 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 mustard greens 'osaka purple'

Pot on seedlings as they grow; not a perennial repot. Mustard Greens 'Osaka Purple'is grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Upright rosette of rounded, smooth-to-lightly-savoyed green leaves washed with purple; quick-growing and bolts to a flowering stalk in heat and long days..

What size pot to step mustard greens 'osaka purple' up to

Pot mustard greens 'osaka purple' 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 mustard greens 'osaka purple'

Pot mustard greens 'osaka purple' 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 mustard greens 'osaka purple'

Pot on before it is root-bound. Check mustard greens 'osaka purple' 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, well-drained loam, ph 6.0-7.5 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 mustard greens 'osaka purple' 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 mustard greens 'osaka purple'

Mustard Greens 'Osaka Purple' wants fertile, moisture-retentive, well-drained loam, ph 6.0-7.5. Prefers rich, nitrogen-rich soil with good organic matter. Keep pH near neutral to deter clubroot common to brassicas. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting mustard greens 'osaka purple' — frequently asked questions

How often should you repot mustard greens 'osaka purple'?

Pot on seedlings as they grow; not a perennial repot for mustard greens 'osaka purple'. Mustard Greens 'Osaka Purple' 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, well-drained loam, ph 6.0-7.5 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 mustard greens 'osaka purple' need?

When is the best time of year to repot mustard greens 'osaka purple'?

Can you put mustard greens 'osaka purple' straight into a much bigger pot?

No. Even a fast-growing mustard greens 'osaka purple' 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 mustard greens 'osaka purple' after repotting?

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