Fertilising guide
How to fertilise Water Spinach 'Pak Boong' (Ipomoea aquatica 'Pak Boong')— schedule & NPK
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.
Growth habit: 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 fertiliser water spinach 'pak boong' actually wants — and why
Water Spinach 'Pak Boong' is grown entirely for its leaves, so nitrogen is the priority — steady, nitrogen-leaning feeding keeps it growing fast, tender and unbolted.
A nitrogen-leaning feed (higher first number) or compost-rich soil — nitrogen drives the fast, tender leafy growth this crop is grown for. Phosphorus and potassium matter far less here than for fruiting crops.
For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for water spinach 'pak boong': match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.
How often to feed water spinach 'pak boong', and which months
Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For water spinach 'pak boong':
Feed generously with nitrogen-rich liquid fertiliser throughout growth to fuel the fast regrowth of stems and leaves after cutting. In practice: a balanced or compost-rich start, then a nitrogen side-dress or liquid feed every 3-4 weeks through the cropping period in the main season (spring through early autumn).
The dormant-season rule matters more than the exact interval: skip feeding entirely when water spinach 'pak boong' is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.
What strength to mix for water spinach 'pak boong'
Use the vegetable-feed label rate for water spinach 'pak boong'. Steady availability matters more than a strong dose — a check in growth makes leaves tough and can trigger bolting.
Feeding always goes onto already-damp soil, never dry roots — water water spinach 'pak boong' first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the water spinach 'pak boong' watering schedule.
Signs you are over-feeding water spinach 'pak boong'
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for water spinach 'pak boong':
- Very soft, floppy, dark-green growth that attracts aphids.
- Excess leafy growth at the expense of hearts/heads in cabbage and the like.
- Salt crust and scorched leaf edges in containers; nitrate-heavy leaves.
Signs you are under-feeding water spinach 'pak boong'
- Pale, yellow-green leaves, oldest first, and slow growth.
- Small, tough, bitter leaves and premature bolting.
- Weak, stunted heads in cabbage, broccoli and cauliflower.
If the symptoms point at watering, light or roots rather than nutrition, the full water spinach 'pak boong' care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
For container-grown water spinach 'pak boong', water until it drains freely each time and flush pots monthly with plain water to stop nitrogen salts accumulating; in the ground, good compost levels naturally buffer this.
Organic vs synthetic feeds for water spinach 'pak boong'
Organic options
Well-rotted manure or compost dug in, plus nitrogen-rich liquid feeds like diluted chicken-manure pellets or nettle feed. UK: pelleted chicken manure or Westland; US: Espoma Garden-tone or blood meal. Steady and soil-building.
Synthetic / liquid feeds
A balanced feed at planting then a high-nitrogen liquid or granular side-dress — UK: Growmore then a nitrogen feed or Phostrogen; US: a 10-10-10 then a high-N (e.g. 21-0-0) side-dress or Miracle-Gro.
Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.
Fertilising water spinach 'pak boong' — frequently asked questions
What fertiliser does water spinach 'pak boong' need?
A nitrogen-leaning feed (higher first number) or compost-rich soil — nitrogen drives the fast, tender leafy growth this crop is grown for. Phosphorus and potassium matter far less here than for fruiting crops. Water Spinach 'Pak Boong' is grown entirely for its leaves, so nitrogen is the priority — steady, nitrogen-leaning feeding keeps it growing fast, tender and unbolted.
How often should I feed water spinach 'pak boong'?
Feed generously with nitrogen-rich liquid fertiliser throughout growth to fuel the fast regrowth of stems and leaves after cutting. Feed generously with nitrogen-rich liquid fertiliser throughout growth to fuel the fast regrowth of stems and leaves after cutting. In practice: a balanced or compost-rich start, then a nitrogen side-dress or liquid feed every 3-4 weeks through the cropping period in the main season (spring through early autumn).
What strength of feed for water spinach 'pak boong'?
Use the vegetable-feed label rate for water spinach 'pak boong'. Steady availability matters more than a strong dose — a check in growth makes leaves tough and can trigger bolting.
What does over-feeding water spinach 'pak boong' look like?
Very soft, floppy, dark-green growth that attracts aphids. Excess leafy growth at the expense of hearts/heads in cabbage and the like. Salt crust and scorched leaf edges in containers; nitrate-heavy leaves. Letting water spinach 'pak boong' run short of nitrogen mid-crop is the main mistake — growth checks, leaves toughen and brassicas/leafy greens bolt or turn bitter. Keep nitrogen steadily available.
Should I flush the soil of water spinach 'pak boong'?
For container-grown water spinach 'pak boong', water until it drains freely each time and flush pots monthly with plain water to stop nitrogen salts accumulating; in the ground, good compost levels naturally buffer this.
Keep reading
- Water Spinach 'Pak Boong' care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water water spinach 'pak boong' — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise tomato
- How to fertilise pepper
- How to fertilise cucumber
- All 5561 fertilising guides in the Growli library