Cold hardiness & minimum temperature

Is Lemon Button Fern (Nephrolepis cordifolia 'Duffii')cold hardy? Hardiness zone & min temp

Also called Button sword fern, Fishbone fern.

More about lemon button fern

About Lemon Button Fern

Nephrolepis cordifolia 'Duffii' · also called Button sword fern, Fishbone fern · houseplant

The Lemon Button Fern is a small, tidy sword fern with upright fronds lined by rounded, button-like leaflets and a faint lemony scent when brushed. More forgiving of average humidity than Boston ferns, it suits terrariums, desks and small pots. It likes moist soil and bright indirect light, and is pet-safe.

Cold limit: USDA 9-11 outdoors; grown as a houseplant in most US homes · RHS H1c (16-24°C)

What lemon button fern's hardiness rating actually means

Lemon Button 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 outdoors; grown as a houseplant 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). Lemon Button Fern has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Lemon Button Fern hardiness — frequently asked questions

Is lemon button fern cold hardy?

Lemon Button 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. Lemon Button Fern can only live outside year-round in genuinely frost-free climates (roughly USDA 9-11 outdoors; grown as a houseplant in most US homes); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature lemon button fern can survive?

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

What hardiness zone is lemon button fern?

Lemon Button Fern is rated USDA 9-11 outdoors; grown as a houseplant in most US homes and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can lemon button 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 lemon button 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.