Herbculinary herbSome care needed

Shiso

Perilla frutescens

Grown as a half-hardy annual and easier than basil in a British summer, which surprises people who assume anything Japanese must be difficult. The red form is as much an ornamental as a herb; the green form is the one used in cooking, and the two are sold interchangeably under the same name.

Position: Full sun or Partial shade
Water: moderate demand
Drainage: Moisture-retentive
Grows to: 45–90 cm × 30–45 cm
Hardiness: H2
Harvest: July to October
Difficulty: Some care needed

Described view

A crisped red shiso leaf quilted between its veins beside a flat green shiso leaf at the same scale

August

Harvest

Shiso’s year

Resolved for United Kingdom (general). Every window is stored against a climate event rather than a date, so a late frost pocket runs later than the band shows. What else August calls for.

Activity	M	A	J	J	A	S	O
Sow under cover	March.	April.
Plant out			June.
Harvest				July.	August.	September.	October.

Timing that travels

The band above resolves this plant's windows into months for one region. These are the windows themselves, stored against a climate event rather than a date — which is the form that survives being carried to a colder garden, a frost pocket, or next year.

What kind of herb this is

Herbs are a kitchen grouping rather than a botanical one, and the plants in it want opposite things. This is the one distinction that decides how to treat it.

Warm-season tender herb

Growing regime

source

Sourced guidancehigh confidence

Royal Horticultural Society: Shiso — growing

Checked 2026-08-13

Does nothing below about 10 °C and sulks in a cold wet spring. Warmth and shelter matter more than feeding, and outdoors in Britain is usually the wrong place until midsummer.

Treated the same way: basil, thai basil. The herb bed, split by regime

Indoors: Indoors spring to autumn

Where the indoor assessment comes from

IndoorsSourced guidancemoderate confidence: Royal Horticultural Society: Shiso — growing indoors
Checked 2026-08-13

Almost any herb will sit on a windowsill in July. This is about whether it is still there in March, which is the part a pot on a supermarket shelf does not tell you.

What happens when it flowers

On a herb this is rarely a problem and rarely nothing. It is the point at which the plant stops being what you grew it for — by a lot, a little, or not at all.

Leaves coarsen

source

Sourced guidancehigh confidence

Royal Horticultural Society: Shiso — harvesting

Checked 2026-08-13

The seed is a crop too

Pinch the flower spikes out to keep the leaves coming, or leave one plant to flower — the seed heads are used in Japanese cooking in their own right, and shiso self-seeds readily enough to return the following year.

source

Sourced guidancemoderate confidence

Royal Horticultural Society: Perilla — growing

Checked 2026-08-13

Conditions it needs

Light: Full sun, Partial shade
Frost: Frost tender
Hardiness rating: H2 (RHS)
Grows best at: 18–28 °C
Soil: Loam, Peat-free compost
Soil pH: 5.5–7
Drainage: Moisture-retentive
Water needs: moderate
Drought: poor tolerance
Waterlogging: poor tolerance
Heat: good tolerance
Wind and exposure: poor tolerance

Where these figures come from

LightSourced guidancemoderate confidence: Royal Horticultural Society: Shiso — position
Checked 2026-08-13
FrostSourced guidancehigh confidence: Royal Horticultural Society: Shiso — hardiness
Checked 2026-08-13
Hardiness ratingSourced guidancemoderate confidence: Royal Horticultural Society: RHS hardiness ratings
Checked 2026-08-13
Grows best atSourced guidancemoderate confidence: Royal Horticultural Society: Shiso — temperature
Checked 2026-08-13
SoilSourced guidancemoderate confidence: Royal Horticultural Society: Shiso — soil
Checked 2026-08-13
Soil pHSourced guidancemoderate confidence: Plant Finder — Missouri Botanical Garden: Perilla frutescens — culture
Checked 2026-08-13
DrainageSourced guidancemoderate confidence: Royal Horticultural Society: Shiso — soil
Checked 2026-08-13
Water needsHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
DroughtHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
WaterloggingHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
HeatHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Wind and exposureHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13

On your soil

Computed by comparing this plant's recorded requirements against each soil's recorded characteristics. A recorded horticultural fact overrides the comparison where GrowingHQ holds one.

Soil	Verdict	Why
Heavy clay	Works, with one condition	Shiso will crop on heavy clay, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. For a crop lifted before winter the risk is not rot but the season: waterlogged ground is cold and unworkable in spring, so sowing is late and germination patchy.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.
Sandy	Works, with one condition	Shiso will crop on sandy, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
Chalky and alkaline	Struggles here	Shiso struggles on chalky and alkaline: The soil is substantially too alkaline for it: it wants pH 5.5 to 7, and this soil sits around 7.8 to 8.5. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering. A container or a raised bed of imported soil sidesteps the problem entirely.
Loam	Prefers this soil	Loam suits Shiso as it stands: The pH suits it: it wants 5.5 to 7, and this soil is in that range. Loam is among the soils it is recorded as suiting. The soil holds moisture, which saves a great deal of watering.
Silty	Grows well here	Shiso grows perfectly well on silty without special measures, though it is not the soil it would choose.
Peaty and acid	Works, with one condition	Shiso will crop on peaty and acid, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. For a crop lifted before winter the risk is not rot but the season: waterlogged ground is cold and unworkable in spring, so sowing is late and germination patchy.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.
Shallow over rock	Works, with one condition	Shiso will crop on shallow over rock, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
Made ground and urban soil	Works, with one condition	Shiso will crop on made ground and urban soil, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. For a crop lifted before winter the risk is not rot but the season: waterlogged ground is cold and unworkable in spring, so sowing is late and germination patchy.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.

Not sure which you have? Four hand tests will settle it.

Space and spacing

Mature height: 45–90 cm
Mature spread: 30–45 cm
Rooting depth: 30 cm
Spacing: 30–40 cm apart

Where these figures come from

Mature heightHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Mature spreadHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Rooting depthHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
SpacingSourced guidancemoderate confidence: Royal Horticultural Society: Shiso — spacing
Checked 2026-08-13

Measured centre to centre. Plants set closer than this compete for light and water long before they look crowded, and the crowding cannot be undone once they are in.

In a container

Minimum volume: 7 litres or more
Minimum depth: 25 cm

Where the container figures come from

Minimum volumeHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Minimum depthHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13

Happy in a pot in a warm sheltered spot outdoors in summer or on a bright sill. Pinch the tips regularly; a container plant runs to flower sooner than one in the ground.

Where and how you can grow it

Each way of growing is assessed separately, and “not assessed” is a real answer rather than a gap we have filled in with a guess.

Method	Suitability	What it needs
Raised bed	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Container	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13	7 litres
Greenhouse	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Polytunnel	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Open ground	Workable source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Traditional dug bed	Workable source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Cold frame	Workable source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Windowsill	Workable source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Hydroponics	Workable source GrowingHQ editorial positionmoderate confidence A soft-leaved tender annual that behaves much like basil, and the purple forms need genuinely bright light or they come up green. GrowingHQ editorial synthesis — GrowingHQ Checked 2026-08-13

Growing it

PropagationSurface-sow and keep the seed in the light. Shiso seed is slow and short-lived, and germination failures are almost always down to burying it or using an old packet rather than to temperature.
PruningPinch the growing tips out from early on to make a bushy plant. Left alone shiso runs up to a single tall stem and produces far fewer of the large leaves it is grown for.
WateringKeep the compost evenly moist through the growing season; shiso wilts dramatically when dry and the leaf quality never fully recovers. It is a tender annual grown for soft new growth, so a plant that has been allowed to dry and harden is better cut back than nursed.
FeedingA dilute balanced liquid feed every two weeks in a container keeps the leaves large and soft. Pinch the growing tips regularly: flowering stops leaf production, and feeding will not compensate for a plant that has been allowed to run up.
HarvestingPick individual leaves from the outside once the plant has half a dozen pairs, taking the larger ones and leaving the growing tip. The flavour is at its best on medium-sized leaves — very young ones are mild and old ones turn coarse. Late in the season the flower spikes are also picked and used, so a plant allowed to run up is not wasted.
ProtectionGrown here as a half-hardy annual: frost ends it and it is not carried through the winter. It will crop well into October in a greenhouse or against a warm wall, which is longer than basil manages. Let one plant set seed and it will often self-sow, and shiso seed needs the winter cold to germinate — so seed left where it fell frequently does better than seed saved and sown in spring.

Where this guidance comes from

PropagationSourced guidancemoderate confidence: Royal Horticultural Society: Shiso — sowing
Checked 2026-08-13
PruningSourced guidancemoderate confidence: Royal Horticultural Society: Shiso — growing
Checked 2026-08-13
WateringSourced guidancemoderate confidence: Royal Horticultural Society: Perilla — cultivation
Checked 2026-08-13
FeedingSourced guidancemoderate confidence: Royal Horticultural Society: Perilla — cultivation
Checked 2026-08-13
HarvestingSourced guidancehigh confidence: Royal Horticultural Society: Shiso — harvesting
Checked 2026-08-13
ProtectionSourced guidancehigh confidence: Royal Horticultural Society: Shiso — cultivation
Checked 2026-08-13

The bud you cut to becomes the new shoot, and it grows in the direction it points — which is why an outward-facing bud opens the plant up and an inward-facing one crosses the middle.

The rule is the same in all four: the new piece needs both a growing point and roots of its own. A cutting is the exception that has to make its roots afterwards, which is why the node matters so much.

Is it worth putting under cover?

Whether it will grow there is on the methods table above. This is whether the space is well spent, which is a different question and usually the one being asked.

Structure	What protection is worth	What decides it
Greenhouse	Extends the season source GrowingHQ editorial positionmoderate confidence What protection is worth for this crop, judged against the same standard as every other record in this file. GrowingHQ editorial synthesis — GrowingHQ Checked 2026-08-13	Frost tenderness and season length. Shiso will grow outdoors in a warm summer and gives far more leaf under cover.
Polytunnel	Extends the season source GrowingHQ editorial positionmoderate confidence What protection is worth for this crop, judged against the same standard as every other record in this file. GrowingHQ editorial synthesis — GrowingHQ Checked 2026-08-13	Frost tenderness and season length.

On a windowsill

Spring to autumn

source

GrowingHQ editorial positionmoderate confidence

How long the crop is actually productive on an ordinary British windowsill without added light.

GrowingHQ editorial synthesis — GrowingHQ

Checked 2026-08-13

Productive from roughly March to October and not after. Growth stops when the light does, and a plant pushed through the dark months usually does not recover. Light and warmth. A good summer sill plant that colours poorly in low light — the purple forms go green before they go leggy, which is a useful early warning.

Growing it without soil

Nearly anything can be grown in a soilless system by somebody with enough equipment. The useful question is whether it is worth it, in which technique, and what goes wrong.

Works with conditions

Succeeds when the conditions listed here are met and fails when they are not. The conditions are the answer, not a caveat.

source

GrowingHQ editorial positionmoderate confidence

A soft-leaved tender annual that behaves much like basil, and the purple forms need genuinely bright light or they come up green.

GrowingHQ editorial synthesis — GrowingHQ

Checked 2026-08-13

Techniques that suit it

Deep water cultureRoots hang in aerated solution. Very productive and very unforgiving of solution temperature — warm solution holds less oxygen and root disease follows.
Nutrient film (NFT)A shallow stream of solution runs over bare roots in a sloped channel. Cheap and productive for small fast crops; a pump failure kills a crop within hours because there is no reservoir at the roots.
Drip-fed mediumSolution is dripped into an inert medium around each plant. The most forgiving technique and the one that suits large, long-season, heavy crops.

source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Root space: Small to moderate.
Lighting: Needs supplementary light
pH band: 5.5–6.5

Where these figures come from

Root spaceHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

LightingHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

pH bandSourced guidancehigh confidence

Outside roughly this band, individual nutrients become unavailable even when they are present in the solution — which is why a crop can starve in a full reservoir.

Purdue Extension — Purdue University: Hydroponic solution management — pH

Checked 2026-08-13

What actually goes wrong

Warm solution. Above roughly 22 °C the water holds much less dissolved oxygen and root disease follows quickly, which is why summer is harder than winter in an indoor system.
source
Sourced guidancemoderate confidence
- Purdue Extension — Purdue University: Solution temperature and dissolved oxygen
Checked 2026-08-13

No nutrient recipes here

GrowingHQ records pH bands, which are measurable properties of nutrient availability, and deliberately records no EC or PPM targets and no mixing instructions. Published targets vary by cultivar, growth stage, water source and technique, and the figures that apply to your system are on the product you bought.

Harvesting

When it is readyReady once the plant has six or so pairs of leaves. Medium-sized leaves have the best flavour — very young ones are mild, and old lower leaves turn coarse. Late in the season the flower spikes are picked and used as well, so a plant running up to flower is still cropping.
How to pick itPick individual leaves from the outside, leaving the growing tip. Use fresh; shiso does not dry.

Where the harvest guidance comes from

When it is readySourced guidancehigh confidence: Royal Horticultural Society: Shiso — harvesting
Checked 2026-08-13
How to pick itHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13

What goes wrong

Problem	How often	Notes
Normal end of an annual's life	common source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13	Yellows from the base once it flowers as the nights draw in.
Slugs and snails	common source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13
Aphids	occasional source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13
Foliage that is meant to look like that	common source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13	The crisped and ruffled forms are grown for a quilted leaf that never flattens, and it is routinely read as virus.

Sources for this page

GrowingHQ editorial synthesis · Plant Finder · Royal Horticultural Society

Each figure on this page carries its own citation, under the “where these figures come from” note in its section. Record last reviewed 2026-08-15.