Fertilising guide
How to fertilise Shiso (Perilla) (Perilla frutescens)— schedule & NPK
Also called Shiso, Perilla, Beefsteak plant, Perilla mint, Japanese basil, Purple mint.
More about shiso (perilla)
About Shiso (Perilla)
Perilla frutescens · also called Shiso, Perilla · herb
Shiso (Perilla frutescens) is a fast-growing, mint-family culinary annual prized in Japanese, Korean and Vietnamese cooking for its fragrant green or purple leaves. Give it warm weather, full sun to light shade and steady moisture. It is not ASPCA-listed but contains perilla ketone, so treat it as mildly toxic and keep curious pets away.
Growth habit: Fast-growing, upright, bushy warm-season annual herb in the mint family (Lamiaceae) with square stems and aromatic, serrated, ovate green or purple leaves. Pinch the tips regularly from about 15 cm (6 in) tall to encourage branching and delay flowering.
What fertiliser shiso (perilla) actually wants — and why
Shiso (Perilla) 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 shiso (perilla): 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 shiso (perilla), 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 shiso (perilla):
Feed every 3-4 weeks during active growth with a balanced or slightly nitrogen-forward liquid fertiliser (such as a 10-10-10 or fish emulsion) at half to full strength to fuel leafy growth. Rich soil amended with compost at planting reduces the need. Avoid over-feeding, which produces lush but blander leaves. 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 shiso (perilla) 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 shiso (perilla)
Half strength is a sensible default for shiso (perilla) — 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 shiso (perilla) first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the shiso (perilla) watering schedule.
Signs you are over-feeding shiso (perilla)
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for shiso (perilla):
- 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 shiso (perilla)
- 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 shiso (perilla) care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Pot-grown shiso (perilla) 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 shiso (perilla)
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 shiso (perilla) — frequently asked questions
What fertiliser does shiso (perilla) 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. Shiso (Perilla) 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 shiso (perilla)?
Feed every 3-4 weeks during active growth with a balanced or slightly nitrogen-forward liquid fertiliser (such as a 10-10-10 or fish emulsion) at half to full strength to fuel leafy growth. Rich soil amended with compost at planting reduces the need. Avoid over-feeding, which produces lush but blander leaves. Feed every 3-4 weeks during active growth with a balanced or slightly nitrogen-forward liquid fertiliser (such as a 10-10-10 or fish emulsion) at half to full strength to fuel leafy growth. Rich soil amended with compost at planting reduces the need. Avoid over-feeding, which produces lush but blander leaves. 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 shiso (perilla)?
Half strength is a sensible default for shiso (perilla) — enough to fuel regrowth after cutting, gentle enough that the leaves stay aromatic rather than watery.
What does over-feeding shiso (perilla) 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 shiso (perilla) 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 shiso (perilla)?
Pot-grown shiso (perilla) 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
- Shiso (Perilla) care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water shiso (perilla) — 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 609 fertilising guides in the Growli library