Fertilising guide
How to fertilise Green Shiso (Perilla frutescens var. frutescens)— schedule & NPK
Also called Green Shiso, Ao Shiso, Green Perilla.
More about green shiso
About Green Shiso
Perilla frutescens var. frutescens · also called Green Shiso, Ao Shiso · herb
Green shiso is a fragrant mint-family annual prized in Japanese cooking for its bright green, frilly, basil-and-anise-scented leaves used with sashimi and tempura. It grows fast in warm conditions, prefers moist, fertile soil and gentle afternoon shade in hot regions, and self-seeds readily. Pinch flower spikes to keep leaves tender and prolong harvest.
Growth habit: Upright, branching aromatic annual with square stems and large, broad, serrated, frilly green leaves; produces slender flower spikes of tiny white flowers in late summer.
What fertiliser green shiso actually wants — and why
Green Shiso is a soft, fast leafy herb that you harvest hard — a modest balanced feed keeps tender growth coming without tipping it into bland or bolting.
A balanced general feed (even N-P-K) at modest strength — enough nitrogen to keep replacing the leaves you pick, but not so much that flavour thins or it bolts to seed.
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:
Moderate feeder grown for leaf. Work compost in at planting and give a balanced or nitrogen-leaning liquid feed every 3-4 weeks to keep new growth tender. In practice: a balanced liquid feed every few weeks through the main growing and harvesting season (spring through early autumn), more often the harder you are picking it.
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
Half strength is a sensible default for green shiso — enough to fuel regrowth after cutting, gentle enough that the leaves stay aromatic rather than watery.
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:
- Fast, soft, pale growth with diluted, less aromatic flavour.
- Early bolting (running to flower) and a bitter edge.
- Salt crust and scorched tips on container plants.
Signs you are under-feeding green shiso
- Pale, slow regrowth after cutting and small leaves.
- A tired, stalled plant that cannot keep up with harvesting.
- Yellowing older leaves in a long-spent pot.
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
Pot-grown green shiso builds up feed salts quickly — water until it drains each time and flush the pot with plain water every few weeks, especially on a sunny windowsill.
Organic vs synthetic feeds for green shiso
Organic options
A diluted seaweed feed or worm-casting tea keeps soft growth coming without overdoing it. UK: dilute seaweed or Westland; US: Espoma Garden-tone or Neptune's Harvest. Gentle, hard to overdo, flavour-friendly.
Synthetic / liquid feeds
A balanced liquid feed at half strength through harvesting — UK: Phostrogen, Baby Bio or Westland; US: Miracle-Gro all-purpose at half strength. Fast regrowth; just do not overdo the nitrogen.
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?
A balanced general feed (even N-P-K) at modest strength — enough nitrogen to keep replacing the leaves you pick, but not so much that flavour thins or it bolts to seed. Green Shiso is a soft, fast leafy herb that you harvest hard — a modest balanced feed keeps tender growth coming without tipping it into bland or bolting.
How often should I feed green shiso?
Moderate feeder grown for leaf. Work compost in at planting and give a balanced or nitrogen-leaning liquid feed every 3-4 weeks to keep new growth tender. Moderate feeder grown for leaf. Work compost in at planting and give a balanced or nitrogen-leaning liquid feed every 3-4 weeks to keep new growth tender. In practice: a balanced liquid feed every few weeks through the main growing and harvesting season (spring through early autumn), more often the harder you are picking it.
What strength of feed for green shiso?
Half strength is a sensible default for green shiso — enough to fuel regrowth after cutting, gentle enough that the leaves stay aromatic rather than watery.
What does over-feeding green shiso look like?
Fast, soft, pale growth with diluted, less aromatic flavour. Early bolting (running to flower) and a bitter edge. Salt crust and scorched tips on container plants. Over-feeding green shiso with strong nitrogen is the usual mistake — it grows fast and lush but the leaves turn bland and it bolts to flower sooner, ending the useful harvest early.
Should I flush the soil of green shiso?
Pot-grown green shiso builds up feed salts quickly — water until it drains each time and flush the pot with plain water every few weeks, especially on a sunny windowsill.
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 basil
- How to fertilise herb garden
- How to fertilise mint
- All 5561 fertilising guides in the Growli library