Cold hardiness & minimum temperature

Is Lemon button fern (Nephrolepis cordifolia)cold hardy? Hardiness zone & min temp

Also called fishbone fern, sword fern, erect sword fern.

About Lemon button fern

Nephrolepis cordifolia · also called fishbone fern, sword fern · houseplant

Lemon button fern is a compact upright fern with small round leaflets that smell faintly of lemon when crushed. More forgiving than Boston fern and pet-safe. Tolerates lower humidity than most ferns.

Tuberous sword fern, a pantropical Nephrolepis that is the only sword fern producing small underground tubers; not native to Florida, where UF/IFAS lists it as a FLEPPC Category I invasive that displaces native vegetation.

Spreads by wiry stolons and wind-dispersed spores (year-round in warm climates) to form dense stands; UF/IFAS and FNGA encouraged phasing it out of the nursery trade, so treat it as a contained-pot plant only.

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

Sources: ask.ifas.ufl.edu, gardeningsolutions.ifas.ufl.edu

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 (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). 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 (indoor 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 (indoor 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.