Cold hardiness & minimum temperature

Is Hydrocotyle tripartita (Hydrocotyle tripartita)cold hardy? Hardiness zone & min temp

Also called Japanese pennywort, trio pennywort.

More about hydrocotyle tripartita

About Hydrocotyle tripartita

Hydrocotyle tripartita · also called Japanese pennywort, trio pennywort · tropical

Hydrocotyle tripartita, Japanese pennywort, is a versatile and forgiving aquatic with small three-lobed clover-like leaves on creeping stems. It can carpet the foreground under bright light or climb hardscape and grow bushy under moderate light. Fast-growing and undemanding, it tolerates a wide range of conditions and needs frequent trimming.

Cold limit: USDA Tropical/subtropical aquarium plant; not frost-hardy, kept in heated aquaria (20-28°C)

What hydrocotyle tripartita's hardiness rating actually means

Hydrocotyle tripartita 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/subtropical aquarium plant; not frost-hardy, kept in heated aquaria — 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). Hydrocotyle tripartita has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for hydrocotyle tripartita 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 hydrocotyle tripartita 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 hydrocotyle tripartita can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Hydrocotyle tripartita hardiness — frequently asked questions

Is hydrocotyle tripartita cold hardy?

Hydrocotyle tripartita 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. Hydrocotyle tripartita can only live outside year-round in genuinely frost-free climates (roughly USDA Tropical/subtropical aquarium plant; not frost-hardy, kept in heated aquaria); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature hydrocotyle tripartita can survive?

What hardiness zone is hydrocotyle tripartita?

Hydrocotyle tripartita is rated USDA Tropical/subtropical aquarium plant; not frost-hardy, kept in heated aquaria and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can hydrocotyle tripartita 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 hydrocotyle tripartita 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.