We are particularly excited about this trial at RHS Garden Wisley, as penstemons have not been trialled by the RHS since the early 1990s. We have 100 varieties down on the Trials Field. As well as the Ice Cream Series, we have many Pensham varieties, originally bred by Edward Wilson in Pensham, Worcestershire, and the Riding Hood series, known for their winter hardiness. Penstemons love the full sun of this untypically hot mid-September and, if the weather holds, should continue to flower through to the autumn, making these a great choice for the late summer garden (often a difficult time to plant for).
Over the next few years the RHS Penstemon Forum will be assessing these plants for the RHS Award of Garden Merit. The forum’s assessments are based on various criteria, including continuity of flowering, pest and disease resistance, hardiness and plant shape and habit.
Penstemons require little maintenance and are generally pest and disease resistant. Regular deadheading through the flowering season will promote new flowers. However, as penstemons are susceptible to frosts, we won’t be cutting the old foliage off until late April or early May of next year, as this provides essential winter protection for new shoots (but a third of the old foliage can be removed in the autumn to prevent wind rock over the winter).
However, as a precaution, we have recently taken cuttings that can be used to replace any penstemons that don’t make it through a severe winter. But let’s hope we don’t need these!