Cold hardiness & minimum temperature

Is Bove's Jerusalem Sage (Phlomis bovei)cold hardy? Hardiness zone & min temp

Also called Bove's Jerusalem sage, Bove's phlomis, Moroccan phlomis.

More about bove's jerusalem sage

About Bove's Jerusalem Sage

Phlomis bovei · also called Bove's Jerusalem sage, Bove's phlomis · flowering

Phlomis bovei is a tall, robust, woolly-leaved shrub native to the Atlas Mountains and dry hillsides of Morocco and Algeria, where it colonises rocky slopes and scrub at low to moderate altitudes. It produces dense whorls of pink to mauve flowers in early summer on stout, felted stems that can reach considerable height, making it an architectural plant for dry Mediterranean or gravel gardens. Its North African origin means it appreciates warmth and resents prolonged cold or wet winters. Phlomis bovei is not included in the ASPCA database and is classified as mildly-toxic as a precautionary measure.

Cold limit: USDA 9-11 · RHS H3 (-3 to 38°C)

Watch for — Winter frost and wet damage: Being of North African origin, this species is less cold-hardy than some European phlomis; protect the crown with a deep grit mulch in zones 9 and below, and bring containerised plants under cover during hard frosts.

What bove's jerusalem sage's hardiness rating actually means

Bove's Jerusalem Sage is half-hardy (RHS H3). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. Its RHS rating of H3 means: Half-hardy — comes through mild UK winters outside but is killed by a hard freeze. On the US scale that maps to USDA 9-11 — 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 −5 to 1 °C — a light, short frost only. Bove's Jerusalem Sage shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for bove's jerusalem sage as it gets too cold:

Down to roughly about −5 to 1 °C it copes, especially if dry and sheltered.
A sustained hard frost collapses the top growth; whether it returns depends on whether the roots, crown or tubers froze.
Wet cold is far more lethal than dry cold for this plant — soggy, frozen soil is the usual killer.

Can bove's jerusalem sage go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 or a frost-free UK microclimate.
In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter.
A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

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 bove's jerusalem sage can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H3 figure above.

Frost protection for borderline bove's jerusalem sage

Bove's Jerusalem Sage is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost.
Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse.
Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones.
Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.

Bove's Jerusalem Sage hardiness — frequently asked questions

Is bove's jerusalem sage cold hardy?

Bove's Jerusalem Sage is half-hardy (RHS H3). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. Borderline outdoors. In its mild end of USDA 9-11 (and sheltered UK gardens) bove's jerusalem sage can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature bove's jerusalem sage can survive?

Minimum survivable temperature is roughly about −5 to 1 °C — a light, short frost only. Bove's Jerusalem Sage shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is bove's jerusalem sage?

Bove's Jerusalem Sage is rated USDA 9-11 and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can bove's jerusalem sage survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 or a frost-free UK microclimate. In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter. A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

How do I protect bove's jerusalem sage from frost?

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost. Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse. Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones. Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.