Fertilising guide
How to fertilise Green Shiso (Perilla frutescens var. crispa f. viridis)— schedule & NPK
Also called Green Shiso, Green Perilla, Ao Shiso, Japanese Basil, Green Beefsteak Plant.
More about green shiso
About Green Shiso
Perilla frutescens var. crispa f. viridis · also called Green Shiso, Green Perilla · edible
An aromatic annual culinary herb essential to Japanese and Korean cuisines, prized for its bright green, frilly-edged leaves with a complex flavour blending mint, basil, anise, and citrus. Used fresh in sushi, salads, tempura, and as a garnish. Thrives in warm, humid conditions with regular harvesting to prevent premature bolting. Grows quickly from seed.
Growth habit: Fast-growing bushy annual; self-seeds prolifically
What fertiliser green shiso actually wants — and why
Green Shiso 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 green shiso: 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 green shiso, 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 green shiso:
Apply a nitrogen-rich balanced liquid fertiliser every 2–3 weeks during the growing season to support lush leafy growth. In rich garden soil, monthly feeding is sufficient. Reduce feeding once flower spikes appear (or remove spikes to prolong leaf harvest). 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 green shiso 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 green shiso
Follow the crop-feed label rate for green shiso — 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 green shiso first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the green shiso watering schedule.
Signs you are over-feeding green shiso
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for green shiso:
- 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 green shiso
- 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 green shiso 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 green shiso 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 green shiso
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 green shiso — frequently asked questions
What fertiliser does green shiso 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. Green Shiso 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 green shiso?
Apply a nitrogen-rich balanced liquid fertiliser every 2–3 weeks during the growing season to support lush leafy growth. In rich garden soil, monthly feeding is sufficient. Reduce feeding once flower spikes appear (or remove spikes to prolong leaf harvest). Apply a nitrogen-rich balanced liquid fertiliser every 2–3 weeks during the growing season to support lush leafy growth. In rich garden soil, monthly feeding is sufficient. Reduce feeding once flower spikes appear (or remove spikes to prolong leaf harvest). 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 green shiso?
Follow the crop-feed label rate for green shiso — 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 green shiso 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 green shiso 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 green shiso?
In containers, fertiliser salts build up fast — water green shiso 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
- Green Shiso care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water green shiso — 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 golden kiwi
- How to fertilise wonderful pomegranate
- How to fertilise dwarf pomegranate
- All 8452 fertilising guides in the Growli library