Cold hardiness & minimum temperature

Is Rue (Ruta graveolens)cold hardy? Hardiness zone & min temp

Also called rue, common rue, herb-of-grace.

More about rue

About Rue

Ruta graveolens · also called rue, common rue · herb

Rue is a woody-based evergreen herb with distinctive blue-green, deeply lobed foliage and clusters of small mustard-yellow summer flowers. Strongly aromatic and historically medicinal, it is now grown mainly as an ornamental and pollinator plant. It thrives in hot, dry, well-drained sites, but its sap causes severe phototoxic skin blistering, so handle it with gloves.

Cold limit: USDA 4-9 (outdoor evergreen sub-shrub) · RHS H5 (10-27°C)

Watch for — Root rot in wet soil: Winter wet and heavy clay cause crown and root rot; plant in sharply drained, gritty soil and avoid overwatering.

What rue's hardiness rating actually means

Yes — rue is genuinely cold hardy. Rated RHS H5 and USDA 4-9 (outdoor evergreen sub-shrub), 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 4-9 (outdoor evergreen sub-shrub) — 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. Rue is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for rue 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 rue go outside or overwinter — and where?

Plant it out within USDA 4-9 (outdoor evergreen sub-shrub) 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 rue can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Rue hardiness — frequently asked questions

Is rue cold hardy?

Yes — rue is genuinely cold hardy. Rated RHS H5 and USDA 4-9 (outdoor evergreen sub-shrub), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Rue is hardy across USDA 4-9 (outdoor evergreen sub-shrub); 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 rue can survive?

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

What hardiness zone is rue?

Rue is rated USDA 4-9 (outdoor evergreen sub-shrub) and RHS H5 — Hardy in most of the UK and in cold winters.

Can rue survive winter outside?

Plant it out within USDA 4-9 (outdoor evergreen sub-shrub) 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 rue 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.