Repotting guide

When & how to repot Water Spinach 'Pak Boong' (Ipomoea aquatica 'Pak Boong')

Also called pak boong, Thai water spinach, swamp morning glory.

More about water spinach 'pak boong'

About Water Spinach 'Pak Boong'

Ipomoea aquatica 'Pak Boong' · also called pak boong, Thai water spinach · edible

'Pak Boong' is the classic Thai water spinach, a slender-leaved kangkong grown for its crisp hollow stems and tender tips used in stir-fries. A heat-loving semi-aquatic vine, it grows explosively in warm, wet conditions, cropping within 4-6 weeks and regrowing after each cut for repeated harvests right through summer.

Mature size: Trailing stems 1-3 m; leaves slender, 10-15 cm; harvested as 20-30 cm shoots

Watch for — Wilting from dryness: Loses turgor and toughens if roots dry out even briefly. Maintain standing water or constantly saturated soil.

How to tell water spinach 'pak boong' needs repotting

Repotting on a calendar is less reliable than reading the plant. For water spinach 'pak boong', 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 water spinach 'pak boong' 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 water spinach 'pak boong'

Pot on seedlings as they grow; not a perennial repot. Water Spinach 'Pak Boong'is grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Vigorous trailing semi-aquatic vine with hollow, jointed stems and narrow arrow-shaped leaves; roots at the nodes and resprouts strongly from cut stems..

What size pot to step water spinach 'pak boong' up to

Pot water spinach 'pak boong' 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 water spinach 'pak boong'

Pot water spinach 'pak boong' 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 water spinach 'pak boong'

Pot on before it is root-bound. Check water spinach 'pak boong' 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, moisture-retentive loam or mud, ph 6.0-7.0 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 water spinach 'pak boong' 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 water spinach 'pak boong'

Water Spinach 'Pak Boong' wants rich, moisture-retentive loam or mud, ph 6.0-7.0. Fertile, heavy, water-holding soil is ideal; it also grows hydroponically. Permanent saturation rather than drainage is what it needs. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting water spinach 'pak boong' — frequently asked questions

How often should you repot water spinach 'pak boong'?

Pot on seedlings as they grow; not a perennial repot for water spinach 'pak boong'. Water Spinach 'Pak Boong' is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into rich, moisture-retentive loam or mud, ph 6.0-7.0 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 water spinach 'pak boong' need?

When is the best time of year to repot water spinach 'pak boong'?

Can you put water spinach 'pak boong' straight into a much bigger pot?

No. Even a fast-growing water spinach 'pak boong' 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 water spinach 'pak boong' after repotting?

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