Cold hardiness & minimum temperature

Is Everlasting Sweet Pea (Lathyrus latifolius)cold hardy? Hardiness zone & min temp

Also called Perennial sweet pea, Everlasting pea.

More about everlasting sweet pea

About Everlasting Sweet Pea

Lathyrus latifolius · also called Perennial sweet pea, Everlasting pea · flowering

The everlasting pea is a tough herbaceous perennial climber that returns yearly from a deep rootstock, throwing out winged stems hung with clusters of pink, rose or white pea flowers all summer. Unlike the annual sweet pea it is scentless but trouble-free, naturalising readily and tolerating poor soil and drought once established.

Cold limit: USDA 5-9 · RHS H5 (-10-25°C)

Watch for — Bare, leggy base: Lower stems can go bare as the plant climbs. Cut back hard after flowering or in late winter to force fresh basal growth.

What everlasting sweet pea's hardiness rating actually means

Yes — everlasting sweet pea is genuinely cold hardy. Rated RHS H5 and USDA 5-9, 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 5-9 — 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. Everlasting Sweet Pea is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for everlasting sweet pea 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 everlasting sweet pea go outside or overwinter — and where?

Plant it out within USDA 5-9 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 everlasting sweet pea can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Everlasting Sweet Pea hardiness — frequently asked questions

Is everlasting sweet pea cold hardy?

Yes — everlasting sweet pea is genuinely cold hardy. Rated RHS H5 and USDA 5-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Everlasting Sweet Pea is hardy across USDA 5-9; 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 everlasting sweet pea can survive?

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

What hardiness zone is everlasting sweet pea?

Everlasting Sweet Pea is rated USDA 5-9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can everlasting sweet pea survive winter outside?

Plant it out within USDA 5-9 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 everlasting sweet pea 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.