Cold hardiness & minimum temperature

Is New Guinea Impatiens (Impatiens hawkeri)cold hardy? Hardiness zone & min temp

Also called New Guinea impatiens, sun impatiens.

More about new guinea impatiens

About New Guinea Impatiens

Impatiens hawkeri · also called New Guinea impatiens, sun impatiens · flowering

New Guinea impatiens are bushy, tender perennials grown as annuals for their large, flat flowers in vivid reds, pinks, oranges, and purples set against dark, often bronze-tinged foliage. More sun- and heat-tolerant than common impatiens and resistant to downy mildew, they bloom non-stop from spring to frost in containers and shaded beds with consistent moisture.

Cold limit: USDA 10-11 (grown as an annual in most US zones) · RHS H2 (16-27°C)

Watch for — Cold damage: Frost-tender; even a light chill blackens foliage. Do not plant out until nights are reliably above 10°C / 50°F.

What new guinea impatiens's hardiness rating actually means

Hardiness works differently for new guinea impatiens: 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 H2 means: Tender — survives a frost-free greenhouse or a very mild, sheltered spot. On the US scale that maps to USDA 10-11 (grown as an annual in most US zones) — 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 new guinea impatiens 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 new guinea impatiens 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 new guinea impatiens can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H2 figure above.

Frost protection for borderline new guinea impatiens

New Guinea Impatiens 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.

New Guinea Impatiens hardiness — frequently asked questions

Is new guinea impatiens cold hardy?

Hardiness works differently for new guinea impatiens: 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. New Guinea Impatiens is grown 10-11 (grown as an annual in most US zones); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature new guinea impatiens 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 new guinea impatiens?

New Guinea Impatiens is rated USDA 10-11 (grown as an annual in most US zones) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can new guinea impatiens 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 new guinea impatiens 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.