Cold hardiness & minimum temperature

Is Sulphur Clover (Trifolium ochroleucon)cold hardy? Hardiness zone & min temp

Also called Sulphur Clover, Cream Clover, Pale-yellow Clover.

More about sulphur clover

About Sulphur Clover

Trifolium ochroleucon · also called Sulphur Clover, Cream Clover · flowering

Trifolium ochroleucon is a clump-forming perennial clover native to Europe and western Asia, grown as an ornamental for its rounded heads of cream to pale-sulphur-yellow flowers held above trifoliate leaves from early to midsummer. It thrives in full sun to dappled shade in well-drained, chalky or loamy soil of moderate fertility, and is particularly suited to dry meadow and pollinator garden schemes. The most important care fact is that it resents heavy, waterlogged soil, which causes root rot and crown death over winter. Trifolium ochroleucon is considered non-toxic to cats and dogs.

Cold limit: USDA 4-9 · RHS H7 (-20 to 25°C)

Watch for — Crown rot in wet winters: The crown and roots are highly susceptible to rotting when soil stays waterlogged through cold, wet winters; plant on a raised bed or slope and add grit to heavy clay soils to ensure drainage.

What sulphur clover's hardiness rating actually means

Yes — sulphur clover is genuinely cold hardy. Rated RHS H7 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. On the US scale that maps to USDA 4-9 — 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 below about −20 °C. Sulphur Clover is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for sulphur clover as it gets too cold:

It tolerates winter lows to about −20 °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 sulphur clover go outside or overwinter — and where?

Plant it out within USDA 4-9 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 sulphur clover can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Sulphur Clover hardiness — frequently asked questions

Is sulphur clover cold hardy?

Yes — sulphur clover is genuinely cold hardy. Rated RHS H7 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Sulphur Clover is hardy across USDA 4-9; 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 sulphur clover can survive?

Minimum survivable temperature is roughly below about −20 °C. Sulphur Clover is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is sulphur clover?

Sulphur Clover is rated USDA 4-9 and RHS H7 — Hardy in the severest European continental winters.

Can sulphur clover survive winter outside?

Plant it out within USDA 4-9 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 sulphur clover below its minimum temperature?

It tolerates winter lows to about −20 °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.