Cold hardiness & minimum temperature

Is Green Shiso (Perilla frutescens var. crispa f. viridis)cold hardy? Hardiness zone & min temp

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.

Cold limit: USDA 2–11 (annual) · RHS H1c (18°C to 35°C)

Watch for — Damping off in cool, wet conditions: Seedlings are susceptible to damping off if sown in cold, waterlogged compost. Sow only when soil temperature is above 18°C, use sterile seed compost, and ensure good drainage and airflow around seedling trays.

What green shiso's hardiness rating actually means

Hardiness works differently for green shiso: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". Its RHS rating of H1c means: Warm-temperate — can summer outdoors but must come in well before the first frost. On the US scale that maps to USDA 2–11 (annual) — the zones where it can be left outdoors year-round.

New to these scales? The USDA hardiness zone map explained covers how the zone numbers work, and you can find your own zone with the zone finder.

Minimum temperature — and what happens below it

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

Concretely, for green shiso as it gets too cold:

Light frost (around 0 to −2 °C) damages or kills tender summer crops outright; cold-hardy types take a few degrees of frost.
The plant does not "survive winter" — its life cycle simply ends, by design, when frost arrives or it finishes cropping.
A surprise late spring frost can also kill young transplants set out too early, before the season even starts.

Can green shiso go outside or overwinter — and where?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost.
In short-season zones, start it indoors or under cover to stretch the effective growing window.
Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

Work back from your local frost dates with the frost-date calculator: the last spring frost and first autumn frost are what really decide when green shiso can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Frost protection for borderline green shiso

Green Shiso is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks.
Have row cover ready for an unexpected late spring or early autumn frost.
Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.

Green Shiso hardiness — frequently asked questions

Is green shiso cold hardy?

Hardiness works differently for green shiso: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". A seasonal crop, not a perennial. Green Shiso is grown 2–11 (annual); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature green shiso can survive?

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

What hardiness zone is green shiso?

Green Shiso is rated USDA 2–11 (annual) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can green shiso survive winter outside?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost. In short-season zones, start it indoors or under cover to stretch the effective growing window. Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

How do I protect green shiso from frost?

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks. Have row cover ready for an unexpected late spring or early autumn frost. Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.