Fertilising guide
How to fertilise Choy Sum 'Green Lance' (Brassica rapa var. parachinensis 'Green Lance')— schedule & NPK
Also called Green Lance choy sum, Chinese flowering cabbage.
More about choy sum 'green lance'
About Choy Sum 'Green Lance'
Brassica rapa var. parachinensis 'Green Lance' · also called Green Lance choy sum, Chinese flowering cabbage · edible
Choy Sum 'Green Lance' is a fast Chinese flowering cabbage grown for sweet, tender flowering stems, leaves, and small yellow buds harvested before full bloom. Quick to mature in 35-50 days, it crops productively in cool seasons and tolerates some heat, regrowing side shoots after the main stem is cut for repeated stir-fry harvests.
Growth habit: Upright, loosely branching plant producing a central flowering stem with green leaves and yellow buds; cutting the main stem stimulates tender side shoots.
What fertiliser choy sum 'green lance' actually wants — and why
Choy Sum 'Green Lance' 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 choy sum 'green lance': 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 choy sum 'green lance', 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 choy sum 'green lance':
Fast, hungry crop: prepare beds with compost or balanced fertiliser, then feed with a nitrogen-rich liquid feed every 2 weeks for lush stems, easing off slightly as flower buds form. 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 choy sum 'green lance' 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 choy sum 'green lance'
Follow the crop-feed label rate for choy sum 'green lance' — 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 choy sum 'green lance' first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the choy sum 'green lance' watering schedule.
Signs you are over-feeding choy sum 'green lance'
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for choy sum 'green lance':
- 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 choy sum 'green lance'
- 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 choy sum 'green lance' 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 choy sum 'green lance' 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 choy sum 'green lance'
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 choy sum 'green lance' — frequently asked questions
What fertiliser does choy sum 'green lance' 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. Choy Sum 'Green Lance' 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 choy sum 'green lance'?
Fast, hungry crop: prepare beds with compost or balanced fertiliser, then feed with a nitrogen-rich liquid feed every 2 weeks for lush stems, easing off slightly as flower buds form. Fast, hungry crop: prepare beds with compost or balanced fertiliser, then feed with a nitrogen-rich liquid feed every 2 weeks for lush stems, easing off slightly as flower buds form. 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 choy sum 'green lance'?
Follow the crop-feed label rate for choy sum 'green lance' — 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 choy sum 'green lance' 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 choy sum 'green lance' 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 choy sum 'green lance'?
In containers, fertiliser salts build up fast — water choy sum 'green lance' 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
- Choy Sum 'Green Lance' care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water choy sum 'green lance' — 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