Cold hardiness & minimum temperature

Is Genovese Basil (Ocimum basilicum 'Genovese')cold hardy? Hardiness zone & min temp

Also called Sweet Basil, Italian Basil.

More about genovese basil

About Genovese Basil

Ocimum basilicum 'Genovese' · also called Sweet Basil, Italian Basil · herb

'Genovese' is the classic Italian sweet basil, with large, glossy, cupped green leaves and a warm, clove-sweet aroma that defines pesto. A tender annual herb, it craves warmth and full sun and sulks in cold, wet soil. Pinch it regularly to keep it bushy and leafy, and it crops abundantly from late spring through summer indoors or out.

Cold limit: USDA Tender annual; grown outdoors in zones 4-11 after frost, year-round indoors · RHS H1c (tender; killed by frost, protect below ~10°C) (18-30°C)

Watch for — Damping off / root rot: Seedlings collapse and mature plants wilt in cold, soggy soil; use free-draining mix, water sparingly in cool weather, and avoid overwatering.

What genovese basil's hardiness rating actually means

Genovese Basil is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. 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 Tender annual; grown outdoors in zones 4-11 after frost, year-round indoors — 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

Minimum survivable temperature is roughly about 5 °C (and never frost). Genovese Basil has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for genovese basil as it gets too cold:

Below about about 5 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches.
A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover.
Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.

Can genovese basil go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 5 °C, in shade or dappled light, hardened off gradually.
Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C.
It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

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 genovese basil can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Genovese Basil hardiness — frequently asked questions

Is genovese basil cold hardy?

Genovese Basil is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Indoor-only in almost every home. Genovese Basil can only live outside year-round in genuinely frost-free climates (roughly USDA Tender annual; grown outdoors in zones 4-11 after frost, year-round indoors); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature genovese basil can survive?

Minimum survivable temperature is roughly about 5 °C (and never frost). Genovese Basil has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is genovese basil?

Genovese Basil is rated USDA Tender annual; grown outdoors in zones 4-11 after frost, year-round indoors and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can genovese basil survive winter outside?

It can holiday outdoors in summer once nights are reliably above 5 °C, in shade or dappled light, hardened off gradually. Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C. It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

What happens to genovese basil below its minimum temperature?

Below about about 5 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches. A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover. Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.