Cold hardiness & minimum temperature

Is Shade Mudflower (Micranthemum umbrosum)cold hardy? Hardiness zone & min temp

Also called Baby's Tears, Pearlweed, Shade Mudwort.

More about shade mudflower

About Shade Mudflower

Micranthemum umbrosum · also called Baby's Tears, Pearlweed · tropical

Micranthemum umbrosum is a lush, small-leaved stem plant forming dense, bright-green bushes in mid- to background aquascapes. It is easier to grow than Hemianthus callitrichoides, tolerating moderate light and lower CO2. Not listed as toxic by the ASPCA; considered pet-safe for aquarium fish, invertebrates, and household pets.

Cold limit: USDA 10–12 (tropical origin; indoor aquarium only in temperate climates) · RHS H1c (20–28°C)

What shade mudflower's hardiness rating actually means

Shade Mudflower 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 10–12 (tropical origin; indoor aquarium only in temperate climates) — 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). Shade Mudflower has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Shade Mudflower hardiness — frequently asked questions

Is shade mudflower cold hardy?

Shade Mudflower 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. Shade Mudflower can only live outside year-round in genuinely frost-free climates (roughly USDA 10–12 (tropical origin; indoor aquarium only in temperate climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature shade mudflower can survive?

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

What hardiness zone is shade mudflower?

Shade Mudflower is rated USDA 10–12 (tropical origin; indoor aquarium only in temperate climates) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can shade mudflower 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 shade mudflower 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.