Cold hardiness & minimum temperature

Is Goldencup St. John's Wort (Hypericum patulum)cold hardy? Hardiness zone & min temp

Also called Goldencup St. John's Wort, Patulum St. Johnswort, Japanese Hypericum.

More about goldencup st. john's wort

About Goldencup St. John's Wort

Hypericum patulum · also called Goldencup St. John's Wort, Patulum St. Johnswort · flowering

Hypericum patulum is a semi-evergreen East Asian shrub bearing large, saucer-shaped golden-yellow flowers from midsummer into autumn. More cold-sensitive than North American Hypericum species, it excels in mild temperate gardens as a border shrub or ground cover. The cultivar 'Hidcote' (often listed under H. 'Hidcote') is one of the most widely planted garden hypericums. Hardy zones 6–9.

Cold limit: USDA 6-9 · RHS H5 (-18°C to 35°C)

Watch for — Frost dieback: In zones 6 and colder, stems may die back in harsh winters. The plant typically resprouts from the base in spring. Cut back dead wood once new growth appears.

What goldencup st. john's wort's hardiness rating actually means

Yes — goldencup st. john's wort is genuinely cold hardy. Rated RHS H5 and USDA 6-9, 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 6-9 — 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. Goldencup St. John's Wort is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for goldencup st. john's wort 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 goldencup st. john's wort go outside or overwinter — and where?

Plant it out within USDA 6-9 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 goldencup st. john's wort can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Goldencup St. John's Wort hardiness — frequently asked questions

Is goldencup st. john's wort cold hardy?

Yes — goldencup st. john's wort is genuinely cold hardy. Rated RHS H5 and USDA 6-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Goldencup St. John's Wort is hardy across USDA 6-9; 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 goldencup st. john's wort can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Goldencup St. John's Wort is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is goldencup st. john's wort?

Goldencup St. John's Wort is rated USDA 6-9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can goldencup st. john's wort survive winter outside?

Plant it out within USDA 6-9 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 goldencup st. john's wort 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.