Fertilising guide
How to fertilise Red Shiso (Perilla frutescens var. crispa 'Atropurpurea')— schedule & NPK
Also called Purple Perilla, Aka Shiso.
More about red shiso
About Red Shiso
Perilla frutescens var. crispa 'Atropurpurea' · also called Purple Perilla, Aka Shiso · herb
Red Shiso is a deep purple-leaved form of perilla, a mint-family annual key to Japanese cuisine, used to colour pickled plums, flavour dishes, and as a garnish. Its frilled burgundy leaves combine culinary and ornamental appeal. A warm-season herb, it loves sun to part shade, fertile moist soil, and warmth, and self-seeds readily.
Growth habit: Upright, bushy mint-family annual with square stems and frilled purple leaves, branching freely when pinched. Flowers on slender spikes in late summer and self-seeds enthusiastically, often returning year after year.
What fertiliser red shiso actually wants — and why
Red 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 red 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 red 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 red shiso:
A moderate feeder grown for abundant leaf. Work compost into the soil and apply a balanced or nitrogen-leaning liquid feed every few weeks for lush growth. Avoid excessive nitrogen, which produces soft leaves at the expense of flavour and colour intensity. 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 red 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 red shiso
Half strength is a sensible default for red 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 red shiso first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the red shiso watering schedule.
Signs you are over-feeding red shiso
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for red 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 red 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 red shiso care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Pot-grown red 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 red 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 red shiso — frequently asked questions
What fertiliser does red 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. Red 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 red shiso?
A moderate feeder grown for abundant leaf. Work compost into the soil and apply a balanced or nitrogen-leaning liquid feed every few weeks for lush growth. Avoid excessive nitrogen, which produces soft leaves at the expense of flavour and colour intensity. A moderate feeder grown for abundant leaf. Work compost into the soil and apply a balanced or nitrogen-leaning liquid feed every few weeks for lush growth. Avoid excessive nitrogen, which produces soft leaves at the expense of flavour and colour intensity. 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 red shiso?
Half strength is a sensible default for red shiso — enough to fuel regrowth after cutting, gentle enough that the leaves stay aromatic rather than watery.
What does over-feeding red 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 red 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 red shiso?
Pot-grown red 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
- Red Shiso care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water red 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 1284 fertilising guides in the Growli library