Cold hardiness & minimum temperature

Is Woolly Jerusalem Sage (Phlomis lanata)cold hardy? Hardiness zone & min temp

Also called Woolly Jerusalem sage, Woolly phlomis.

More about woolly jerusalem sage

About Woolly Jerusalem Sage

Phlomis lanata · also called Woolly Jerusalem sage, Woolly phlomis · flowering

Phlomis lanata is a low, mound-forming, evergreen sub-shrub native to Crete and the Greek islands, where it grows on dry rocky hillsides and garrigue scrub. It is prized for its exceptionally dense, white-woolly leaves and whorls of bright yellow flowers borne in late spring and early summer. Excellent drainage and full sun are non-negotiable — this species is very intolerant of winter wet. Phlomis lanata is not listed on the ASPCA database; it is classified here as mildly-toxic due to insufficient confirmed safety data.

Cold limit: USDA 8-11 · RHS H4 (-5 to 35°C)

Watch for — Winter wet / root rot: Wet, cold soils in autumn and winter are the primary killer; plant in raised beds or on slopes with added grit, and avoid overhead irrigation in autumn.

What woolly jerusalem sage's hardiness rating actually means

Yes — woolly jerusalem sage is genuinely cold hardy. Rated RHS H4 and USDA 8-11, 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 8-11 — 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. Woolly Jerusalem Sage is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for woolly jerusalem sage 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 woolly jerusalem sage go outside or overwinter — and where?

Plant it out within USDA 8-11 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 woolly jerusalem sage can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Woolly Jerusalem Sage hardiness — frequently asked questions

Is woolly jerusalem sage cold hardy?

Yes — woolly jerusalem sage is genuinely cold hardy. Rated RHS H4 and USDA 8-11, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Woolly Jerusalem Sage is hardy across USDA 8-11; 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 woolly jerusalem sage can survive?

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

What hardiness zone is woolly jerusalem sage?

Woolly Jerusalem Sage is rated USDA 8-11 and RHS H4 — Hardy in an average winter across much of the temperate world.

Can woolly jerusalem sage survive winter outside?

Plant it out within USDA 8-11 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 woolly jerusalem sage 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.