Cold hardiness & minimum temperature

Is Cosson's Germander (Teucrium cossonii)cold hardy? Hardiness zone & min temp

Also called Cosson's germander, Balearic germander.

More about cosson's germander

About Cosson's Germander

Teucrium cossonii · also called Cosson's germander, Balearic germander · flowering

Teucrium cossonii is a low-growing, prostrate sub-shrub endemic to the Balearic Islands (Majorca and Ibiza), where it scrambles over sun-baked limestone rocks and coastal scrub. It is grown for its dense silver-grey felted foliage and bright cerise to pink-purple flowers produced over a long summer season. The most important care consideration is outstanding drainage and full sun — waterlogged roots in winter cause rapid death, making it best suited to a dry wall top, raised scree bed, or alpine house in wetter climates. Treat as mildly toxic to pets, consistent with the Teucrium genus.

Cold limit: USDA 7-10 · RHS H4 (-8 to 35°C)

Watch for — Root rot in winter wet: The primary cause of losses in UK and PNW gardens; even short periods of waterlogging during cold weather rot the fine roots and crown. Grow in raised scree beds or against a dry, south-facing wall.

What cosson's germander's hardiness rating actually means

Yes — cosson's germander is genuinely cold hardy. Rated RHS H4 and USDA 7-10, 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 7-10 — 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. Cosson's Germander is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for cosson's germander 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 cosson's germander go outside or overwinter — and where?

Plant it out within USDA 7-10 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 cosson's germander can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Frost protection for borderline cosson's germander

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

At the cold edge of its range, mulch the root zone in late autumn to buffer the deepest freezes.
Protect container specimens — pots freeze through far faster than open ground, costing roughly a zone of hardiness.
Shelter new growth from late spring frosts with fleece if a hard night is forecast.

Cosson's Germander hardiness — frequently asked questions

Is cosson's germander cold hardy?

Yes — cosson's germander is genuinely cold hardy. Rated RHS H4 and USDA 7-10, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Cosson's Germander is hardy across USDA 7-10; 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 cosson's germander can survive?

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

What hardiness zone is cosson's germander?

Cosson's Germander is rated USDA 7-10 and RHS H4 — Hardy in an average winter across much of the temperate world.

Can cosson's germander survive winter outside?

Plant it out within USDA 7-10 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.

How do I protect cosson's germander from frost?

At the cold edge of its range, mulch the root zone in late autumn to buffer the deepest freezes. Protect container specimens — pots freeze through far faster than open ground, costing roughly a zone of hardiness. Shelter new growth from late spring frosts with fleece if a hard night is forecast.