Fertilising guide
How to fertilise Pak Choi (Brassica rapa subsp. chinensis)— schedule & NPK
Also called Bok choy, Chinese cabbage, Pak choy.
More about pak choi
About Pak Choi
Brassica rapa subsp. chinensis · also called Bok choy, Chinese cabbage · edible
Pak choi is a fast, succulent Asian brassica grown for its crisp white or green leaf stalks and tender dark leaves in a loose, non-heading rosette. It crops in as little as 4-8 weeks and is ideal for stir-fries. Quick and easy, it suits spring and late-summer sowings; hot, dry conditions and long days readily trigger bolting, so cool, moist growing is key.
Growth habit: Compact, non-heading rosette of upright, spoon-shaped leaves on thick, fleshy, overlapping leaf stalks that flare from a short central base.
What fertiliser pak choi actually wants — and why
Pak Choi feeds in two distinct phases — balanced to build the plant, then high-potassium the moment flowering starts to set and fill a heavy crop.
Balanced (even N-P-K) at planting for roots and frame, then switch to a high-potassium ("high-potash") tomato-style feed once the first flowers open — potassium is what sizes and ripens fruit, not nitrogen.
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 pak choi: 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 pak choi, 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 pak choi:
Light-to-moderate feeder grown fast and young. Fertile soil enriched with compost usually suffices; on poorer ground, a nitrogen-rich liquid feed every couple of weeks keeps growth rapid and leaves tender. Avoid stalling growth, which toughens the crop. So: a balanced feed or compost at planting, then a high-potash liquid every 1-2 weeks from first flower through harvest across the main season (spring through early autumn).
The dormant-season rule matters more than the exact interval: skip feeding entirely when pak choi 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 pak choi
Follow the crop-feed label rate for pak choi — these are calibrated for hungry vegetables. Consistency through fruiting matters more than strength; erratic feeding causes problems like blossom-end rot.
Feeding always goes onto already-damp soil, never dry roots — water pak choi first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the pak choi watering schedule.
Signs you are over-feeding pak choi
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for pak choi:
- Vigorous dark-green leafy growth but few flowers or fruit (excess nitrogen).
- Lush foliage hiding the crop; soft growth prone to pests and disease.
- Salt crust on the soil and scorched leaf edges in containers.
Signs you are under-feeding pak choi
- Pale, yellowing lower leaves and stunted growth.
- Small fruit, poor set, and a quickly exhausted plant.
- Blossom-end rot and weak cropping from erratic or insufficient feeding.
If the symptoms point at watering, light or roots rather than nutrition, the full pak choi care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
In containers, fertiliser salts build up fast — water pak choi thoroughly so excess drains from the base each time, and flush pots with plain water every few weeks to prevent a damaging salt build-up.
Organic vs synthetic feeds for pak choi
Organic options
Garden compost or well-rotted manure dug in before planting, plus a liquid comfrey or seaweed feed once fruiting starts. UK: comfrey feed or organic Tomorite; US: Espoma Tomato-tone or Neptune's Harvest. Builds soil and feeds in one.
Synthetic / liquid feeds
A balanced feed at planting then a high-potash tomato feed in fruiting — UK: Growmore at planting then Tomorite (Levington) or Phostrogen; US: a balanced 10-10-10 then Miracle-Gro Tomato or a bloom booster.
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 pak choi — frequently asked questions
What fertiliser does pak choi need?
Balanced (even N-P-K) at planting for roots and frame, then switch to a high-potassium ("high-potash") tomato-style feed once the first flowers open — potassium is what sizes and ripens fruit, not nitrogen. Pak Choi feeds in two distinct phases — balanced to build the plant, then high-potassium the moment flowering starts to set and fill a heavy crop.
How often should I feed pak choi?
Light-to-moderate feeder grown fast and young. Fertile soil enriched with compost usually suffices; on poorer ground, a nitrogen-rich liquid feed every couple of weeks keeps growth rapid and leaves tender. Avoid stalling growth, which toughens the crop. Light-to-moderate feeder grown fast and young. Fertile soil enriched with compost usually suffices; on poorer ground, a nitrogen-rich liquid feed every couple of weeks keeps growth rapid and leaves tender. Avoid stalling growth, which toughens the crop. So: a balanced feed or compost at planting, then a high-potash liquid every 1-2 weeks from first flower through harvest across the main season (spring through early autumn).
What strength of feed for pak choi?
Follow the crop-feed label rate for pak choi — these are calibrated for hungry vegetables. Consistency through fruiting matters more than strength; erratic feeding causes problems like blossom-end rot.
What does over-feeding pak choi look like?
Vigorous dark-green leafy growth but few flowers or fruit (excess nitrogen). Lush foliage hiding the crop; soft growth prone to pests and disease. Salt crust on the soil and scorched leaf edges in containers. Staying on a high-nitrogen feed once pak choi starts flowering is the classic error — you get a huge leafy plant and a disappointing crop. Switch to high-potash the moment flowers appear.
Should I flush the soil of pak choi?
In containers, fertiliser salts build up fast — water pak choi thoroughly so excess drains from the base each time, and flush pots with plain water every few weeks to prevent a damaging salt build-up.
Keep reading
- Pak Choi care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water pak choi — 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 1284 fertilising guides in the Growli library