Cold hardiness & minimum temperature
Is Echinodorus cordifolius (Echinodorus cordifolius)cold hardy? Hardiness zone & min temp
Also called radicans sword, spade-leaf sword.
More about echinodorus cordifolius
About Echinodorus cordifolius
Echinodorus cordifolius · also called radicans sword, spade-leaf sword · tropical
A large marsh sword from the Americas with broad, spade- to heart-shaped leaves on long petioles. A vigorous grower, it readily sends leaves emersed above the waterline and is well suited to open-top tanks and paludariums. It feeds heavily through its roots and propagates prolifically from plantlets on its long flower stalks.
Cold limit: USDA Tropical-to-subtropical marsh plant — not frost hardy; keep above 15°C (20-28°C)
What echinodorus cordifolius's hardiness rating actually means
Echinodorus cordifolius 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 H1b means: Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season. On the US scale that maps to USDA Tropical-to-subtropical marsh plant — not frost hardy; keep above 15°C — 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 10 °C (sustained cold below this is damaging). Echinodorus cordifolius has no frost tolerance at all — it is an indoor plant in any climate with a real winter.
Concretely, for echinodorus cordifolius as it gets too cold:
- Below about about 10 °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 echinodorus cordifolius go outside or overwinter — and where?
- It can holiday outdoors in summer once nights are reliably above 10 °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 echinodorus cordifolius can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.
Echinodorus cordifolius hardiness — frequently asked questions
Is echinodorus cordifolius cold hardy?
Echinodorus cordifolius 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. Echinodorus cordifolius can only live outside year-round in genuinely frost-free climates (roughly USDA Tropical-to-subtropical marsh plant — not frost hardy; keep above 15°C); everywhere else it is a houseplant that summers out at most.
What is the minimum temperature echinodorus cordifolius can survive?
Minimum survivable temperature is roughly about 10 °C (sustained cold below this is damaging). Echinodorus cordifolius has no frost tolerance at all — it is an indoor plant in any climate with a real winter.
What hardiness zone is echinodorus cordifolius?
Echinodorus cordifolius is rated USDA Tropical-to-subtropical marsh plant — not frost hardy; keep above 15°C and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.
Can echinodorus cordifolius survive winter outside?
It can holiday outdoors in summer once nights are reliably above 10 °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 echinodorus cordifolius below its minimum temperature?
Below about about 10 °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.
Keep reading
- Echinodorus cordifolius care — the full brief (light, water, soil, problems, pet safety)
- USDA hardiness zones — find yours and what grows there
- Is echinodorus cordifolius hardy in the UK? — the RHS-rating version
- RHS hardiness ratings — the UK system explained
- Frost-date calculator — your real outdoor window
- The USDA hardiness zone map, explained
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- All 5561plant hardiness & min-temp guides