There can be no denying that Digitalis ‘Illumination Pink‘ is a stunning plant, it fits perfectly into a pale pink, yellows and orange border that is being creating at Plant Enthusiast Towers. However while my heart loves this stunning plant, my head also knows I will be buying a new one next year as they are simply not hardy in my East Yorkshire garden.
However this was not to be the case, and it has now survived three winters in East Yorkshire.
Plant breeder Thompson & Morgan did reduced the hardiness rating for this plant, which won the 2012 Chelsea Flower Show Plant of the Year title from hardy to half hardy in 2014.
Paul Hansord, Horticultural Director at Thompson and Morgan in an interview for Trade Magazine Horticulture Week stated that Illumination Pink has been hardy in many customers gardens, and that they had whole fields of ‘Illumination Pink’ which had made it through the winter.
This raises the interesting question of what is hardiness?
How can a plant that survives in a field in Ipswich, fail in so many peoples gardens every year.
Well hardiness is many things:
It is what the top of the plant experiences, the late sun to ripen and harden foliage (which is not relevant with herbaceous plants) it is the air temperature around the plant and the presence of ice or snow on leaves overwinter.
It is what the root of the plant experiences, soil temperature and the moisture level in the soil.
Hardiness is a complex mix of these factors and so while ‘Illumination pink’ may be hardy in a well drained sandy field, it may fail in a warmer position with poor drainage on a heavy soil.
The best advice to plant breeders was given by Jim Gardiner, who was referring to Anemone “White Swan” (Winner of the 2011 RHS Chelsea Flower Show Plant of the Year, which also has questionable hardiness in our climate) – plant breeders should follow up awards with the RHS Award of Garden Merit trials to give an indication of both hardiness and reliability.