Cold hardiness & minimum temperature

Is Kimberly queen fern (Nephrolepis obliterata)cold hardy? Hardiness zone & min temp

Also called sword fern, erect sword fern.

About Kimberly queen fern

Nephrolepis obliterata · also called sword fern, erect sword fern · houseplant

Kimberly queen fern is an upright Australian relative of the Boston fern, more tolerant of dry air and tidier in growth habit. Pet-safe and a popular porch and indoor fern. Less needle-drop than Boston fern.

Nephrolepis obliterata, the Australian sword fern, native to Australia and adapted to warm, humid conditions; hardy outdoors only in USDA zones 9-11.

Distinctive upright, narrow, sword-shaped fronds forming a dense bushy clump (about 60-90cm), and it rarely sheds leaflets, unlike the messier drooping Boston fern; reported non-toxic to cats and dogs.

Cold limit: USDA 9-11 (indoor in most US homes) · RHS H1c (15-24°C)

Sources: provenwinners.com, gardenia.net

What kimberly queen fern's hardiness rating actually means

Kimberly queen fern 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 9-11 (indoor in most US homes) — 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). Kimberly queen fern has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for kimberly queen fern 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 kimberly queen fern 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 kimberly queen fern can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Kimberly queen fern hardiness — frequently asked questions

Is kimberly queen fern cold hardy?

Kimberly queen fern 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. Kimberly queen fern can only live outside year-round in genuinely frost-free climates (roughly USDA 9-11 (indoor in most US homes)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature kimberly queen fern can survive?

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

What hardiness zone is kimberly queen fern?

Kimberly queen fern is rated USDA 9-11 (indoor in most US homes) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can kimberly queen fern 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 kimberly queen fern 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.