Cold hardiness & minimum temperature

Is Knotted Clover (Trifolium striatum)cold hardy? Hardiness zone & min temp

Also called Knotted Clover, Soft Trefoil.

More about knotted clover

About Knotted Clover

Trifolium striatum · also called Knotted Clover, Soft Trefoil · flowering

Trifolium striatum is a low-growing annual clover native to Europe and western Asia, typically found on dry, sandy or gravelly grasslands, heathlands, and disturbed ground where it is often a scarce plant of conservation interest in the UK. It thrives in full sun on free-draining, nutrient-poor soils and is well adapted to dry conditions. The most important care fact is that it requires open, low-competition ground to establish from seed, as it cannot compete with coarser vegetation. Trifolium striatum is considered non-toxic to cats and dogs.

Cold limit: USDA 5-9 · RHS H5 (-15 to 28°C)

What knotted clover's hardiness rating actually means

Yes — knotted clover is genuinely cold hardy. Rated RHS H5 and USDA 5-9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 5-9 — 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 about −15 to −10 °C. Knotted Clover is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for knotted clover as it gets too cold:

It tolerates winter lows to about −15 to −10 °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 knotted clover go outside or overwinter — and where?

Plant it out within USDA 5-9 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 knotted clover can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Knotted Clover hardiness — frequently asked questions

Is knotted clover cold hardy?

Yes — knotted clover is genuinely cold hardy. Rated RHS H5 and USDA 5-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Knotted Clover is hardy across USDA 5-9; 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 knotted clover can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Knotted Clover is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is knotted clover?

Knotted Clover is rated USDA 5-9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can knotted clover survive winter outside?

Plant it out within USDA 5-9 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 knotted clover below its minimum temperature?

It tolerates winter lows to about −15 to −10 °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.