UK hardiness
Is Johnny Jump Up hardy in the UK?
Viola tricolor
More about johnny jump up in the UK
Johnny Jump Up and the RHS hardiness rating
Johnny Jump Up is rated RHS H5 (hardy to around -15°C) — hardy in a cold winter, meaning it withstands winter minimums of about -15 to -10°C. In practice that means it hardy through most of the UK even in severe winters. The RHS rating describes an absolute minimum temperature, not an average: a single hard frost below its band is what does the damage, so the question is always "what is the coldest night my garden gets?", not "what is a typical winter here?".
This follows the RHS plant hardiness rating system (H1a–H7), the UK standard. For the US growing-zone view, see the johnny jump up USDA hardiness guide.
Does UK region change it?
UK winters vary far more by locality than by latitude. Mild western and coastal areas (the south-west, Pembrokeshire, western Scotland's coast) and urban heat islands run several degrees warmer than inland frost pockets, valleys, and exposed eastern sites at the same latitude. A plant marginal on its RHS rating often survives in a sheltered town garden but fails 20 miles inland — so judge by your own coldest recorded night and microclimate (a south-facing wall, a courtyard) rather than the regional average.
Overwintering johnny jump up in the UK
For a borderline-hardy plant, the UK winter killers are not just cold air but cold wet roots and wind. Improve drainage before winter, mulch the root zone, move containers to a sheltered spot or against a warm wall, and use horticultural fleece on hard-frost nights. Established plants in free-draining soil take far more cold than a recently planted one in heavy, wet ground.
Johnny Jump Up UK hardiness — frequently asked questions
Is johnny jump up hardy in the UK?
Johnny Jump Up is rated RHS H5 (hardy to around -15°C) (hardy in a cold winter, hardy to about -15 to -10°C). It hardy through most of the UK even in severe winters.
Can johnny jump up stay outside over winter in the UK?
In most of the UK, yes, if your garden's coldest night stays within its RHS H5 (hardy to around -15°C) band (around -15 to -10°C). In colder inland or northern gardens, give it a sheltered spot, sharp drainage, and fleece on hard-frost nights.
What does RHS H5 (hardy to around -15°C) mean?
RHS hardiness ratings run H1a (needs a heated glasshouse) to H7 (survives below -20°C). Johnny Jump Up's rating, H5 (hardy to around -15°C), means hardy in a cold winter — it tolerates winter minimums of about -15 to -10°C. The rating is an absolute minimum, not an average.
How do I overwinter johnny jump up in the UK?
For a borderline-hardy plant, the UK winter killers are not just cold air but cold wet roots and wind. Improve drainage before winter, mulch the root zone, move containers to a sheltered spot or against a warm wall, and use horticultural fleece on hard-frost nights. Established plants in free-draining soil take far more cold than a recently planted one in heavy, wet ground.
Does UK region change whether johnny jump up survives?
UK winters vary far more by locality than by latitude. Mild western and coastal areas (the south-west, Pembrokeshire, western Scotland's coast) and urban heat islands run several degrees warmer than inland frost pockets, valleys, and exposed eastern sites at the same latitude. A plant marginal on its RHS rating often survives in a sheltered town garden but fails 20 miles inland — so judge by your own coldest recorded night and microclimate (a south-facing wall, a courtyard) rather than the regional average.
More johnny jump up care
See the full johnny jump up care guide, its temperature & humidity needs, and the US (USDA) hardiness version of this page.