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Penstemons by hardiness

Some penstemons are hardier than others and, as a general guide, the thinner the leaves the hardier they are. If you have a sandy soil, that drains well, your penstemons will fare better through cold, damp winters than if you have a clay soil. All plant hardiness ratings are based on plants growing in the UK.

Tender penstemons

Hardiness rating 3 (-5°C to 1°C). Hardy in coastal / mild areas except in hard winters and at risk from sudden (early) frosts. May be hardy elsewhere with wall shelter or good microclimate. Can survive with artificial winter protection.

Hardy penstemons

Hardiness rating 4 (-10°C to -5°C). Hardy through most of the UK apart from inland valleys, at altitude and central / northerly locations. May suffer foliage damage and stem dieback in harsh winters in cold gardens. Plants in pots are more vulnerable.

Hardiest penstemons

Hardiness rating 5 (-15°C to -10°C). Hardy through most of the UK even in severe winters. May not withstand open or exposed sites or central / northerly locations. Many evergreens suffer foliage damage and plants in pots will be at increased risk.

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