Cold hardiness & minimum temperature

Is Arrowhead 'Kuwai' (Sagittaria trifolia var. sinensis)cold hardy? Hardiness zone & min temp

Also called kuwai, Chinese arrowhead, Japanese arrowhead tuber.

More about arrowhead 'kuwai'

About Arrowhead 'Kuwai'

Sagittaria trifolia var. sinensis · also called kuwai, Chinese arrowhead · edible

Kuwai (Sagittaria trifolia var. sinensis) is an aquatic perennial grown in flooded paddies for its rounded, blue-tinged corms, a prized New Year vegetable in Japan and China. The plant bears distinctive arrow-shaped emergent leaves and whorled white flowers. Its starchy tubers, slightly bitter raw, are peeled and simmered; they are always cooked, never eaten raw, and the plant needs standing water to crop.

Cold limit: USDA 6-10 (corms overwinter in mud below the frost line; tops are frost-tender) · RHS H4 (18-30°C)

Watch for — Frost on top growth: Foliage is killed by frost, cutting the season short in cool climates. Plant after the last frost and harvest corms before hard freezes, or overwinter them deep in unfrozen mud.

What arrowhead 'kuwai''s hardiness rating actually means

Yes — arrowhead 'kuwai' is genuinely cold hardy. Rated RHS H4 and USDA 6-10 (corms overwinter in mud below the frost line; tops are frost-tender), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 6-10 (corms overwinter in mud below the frost line; tops are frost-tender) — 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 to −5 °C. Arrowhead 'Kuwai' is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for arrowhead 'kuwai' as it gets too cold:

It tolerates winter lows to about −10 to −5 °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 arrowhead 'kuwai' go outside or overwinter — and where?

Plant it out within USDA 6-10 (corms overwinter in mud below the frost line; tops are frost-tender) 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 arrowhead 'kuwai' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Arrowhead 'Kuwai' hardiness — frequently asked questions

Is arrowhead 'kuwai' cold hardy?

Yes — arrowhead 'kuwai' is genuinely cold hardy. Rated RHS H4 and USDA 6-10 (corms overwinter in mud below the frost line; tops are frost-tender), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Arrowhead 'Kuwai' is hardy across USDA 6-10 (corms overwinter in mud below the frost line; tops are frost-tender); 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 arrowhead 'kuwai' can survive?

Minimum survivable temperature is roughly about −10 to −5 °C. Arrowhead 'Kuwai' is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is arrowhead 'kuwai'?

Arrowhead 'Kuwai' is rated USDA 6-10 (corms overwinter in mud below the frost line; tops are frost-tender) and RHS H4 — Hardy in an average winter across much of the temperate world.

Can arrowhead 'kuwai' survive winter outside?

Plant it out within USDA 6-10 (corms overwinter in mud below the frost line; tops are frost-tender) 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 arrowhead 'kuwai' below its minimum temperature?

It tolerates winter lows to about −10 to −5 °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.