Cold hardiness & minimum temperature

Is Forsythia Sage (Salvia madrensis)cold hardy? Hardiness zone & min temp

Also called Forsythia sage, Yellow mountain sage.

More about forsythia sage

About Forsythia Sage

Salvia madrensis · also called Forsythia sage, Yellow mountain sage · flowering

Forsythia sage is a robust, tall-growing perennial subshrub from the Sierra Madre Occidental highlands of Mexico, producing striking, terminal spikes of butter-yellow flowers in autumn that resemble forsythia blossom from a distance. It prefers fertile, well-drained soil with regular moisture during the growing season and benefits from a sheltered site in cooler climates. As a late-season bloomer, it is most valuable when most other sages have finished flowering. Salvia is listed as non-toxic to cats and dogs by the ASPCA.

Cold limit: USDA 8-11 · RHS H3 (-3 to 35 °C)

Watch for — Frost dieback: Top growth is cut by frost below about -3 °C, but established crowns reshoot from the base in spring if the roots are mulched over winter.

What forsythia sage's hardiness rating actually means

Forsythia 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 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 −5 to 1 °C — a light, short frost only. Forsythia Sage shrugs off cold nights but a real, sustained freeze will kill it.

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

It can live outside year-round only in the mildest, most sheltered part of USDA 8-11 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 forsythia 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 forsythia sage

Forsythia 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.

Forsythia Sage hardiness — frequently asked questions

Is forsythia sage cold hardy?

Forsythia 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 8-11 (and sheltered UK gardens) forsythia 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 forsythia sage can survive?

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

What hardiness zone is forsythia sage?

Forsythia Sage is rated USDA 8-11 and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can forsythia sage survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-11 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 forsythia 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.