Cold hardiness & minimum temperature

Is Lemna minor (Lemna minor)cold hardy? Hardiness zone & min temp

Also called Common Duckweed, Lesser Duckweed, Bayroot.

More about lemna minor

About Lemna minor

Lemna minor · also called Common Duckweed, Lesser Duckweed · houseplant

Common duckweed is a tiny free-floating aquatic plant, each frond just 2-4 mm across with a single dangling root. It multiplies explosively to carpet still water in green, shading out algae and oxygenating fish ponds and aquariums. Useful for nutrient uptake and shade, but it spreads so fast it must be skimmed back regularly to avoid blanketing the surface.

Cold limit: USDA 4-10 (overwinters as sinking turions in cold ponds) · RHS H5 (6 to 33°C)

Watch for — Winter die-back: Fronds form turions and sink in cold water, vanishing each autumn; this is normal — they resurface and regrow when water warms in spring.

What lemna minor's hardiness rating actually means

Yes — lemna minor is genuinely cold hardy. Rated RHS H5 and USDA 4-10 (overwinters as sinking turions in cold ponds), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 4-10 (overwinters as sinking turions in cold ponds) — 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 −15 to −10 °C. Lemna minor is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for lemna minor as it gets too cold:

It tolerates winter lows to about −15 to −10 °C once established.
Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root.
First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.

Can lemna minor go outside or overwinter — and where?

Plant it out within USDA 4-10 (overwinters as sinking turions in cold ponds) and it overwinters with little or no help.
It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy.
The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

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 lemna minor can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Lemna minor hardiness — frequently asked questions

Is lemna minor cold hardy?

Yes — lemna minor is genuinely cold hardy. Rated RHS H5 and USDA 4-10 (overwinters as sinking turions in cold ponds), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Lemna minor is hardy across USDA 4-10 (overwinters as sinking turions in cold ponds); it belongs in the ground or a frost-proof container, not on a windowsill, and many types actively need a cold winter to perform.

What is the minimum temperature lemna minor can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Lemna minor is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is lemna minor?

Lemna minor is rated USDA 4-10 (overwinters as sinking turions in cold ponds) and RHS H5 — Hardy in most of the UK and in cold winters.

Can lemna minor survive winter outside?

Plant it out within USDA 4-10 (overwinters as sinking turions in cold ponds) and it overwinters with little or no help. It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy. The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

What happens to lemna minor below its minimum temperature?

It tolerates winter lows to about −15 to −10 °C once established. Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root. First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.