The penstemons at Lamberhurst Cottage this year are flowering early and well due, I suspect, to the relatively dry and mild start to summer. The first flush of the mauve-blue flowers of the cultivar 'Catherine de la Mare' have come and gone. Its larger cousin 'Alice Hindley' (pictured above and sometimes called 'Lady Alice Hindley' or Handley) is in full bloom together with 'Evelyn' (sometimes called 'Phyllis'), 'Snow Storm' (a synonym for 'White Bedder'), 'Schoenholzeri' (commonly known as 'Firebird' in English-speaking countries) and a number of the Hidcote varieties. Other cultivars like 'Sour Grapes', 'Russian Blue' and 'Blackbird' are on the brink of flowering.
These are but a few of the hundreds of garden forms of penstemons known to be in cultivation today. The penstemon (or pentstemon as it was once spelt) is a product of the 'New World' where over 270 species of the genus were found spread across the United States, Canada and Mexico. Pursued by botanists and plant hunters from the mid-1700s, the North American penstemons began to be hybridised, largely in the United Kingdom and Europe, from the early 1800s. The initial favourites among growers were those cultivars that exhibited the large and brightly coloured flowers that were planted en masse in public and private garden beds in the Victorian era. With the advent of Gertude Jekyl's herbaceous borders, and under the influence of Henry Robinson and other garden writers, tastes eventually changed towards medium-sized varieties with bushier and more upright habits and flowers that were longer lasting and more subdued in colour. In recent years the interest in more 'sporty' hues has returned and penstemons of all shapes, sizes and colours are featured in (usually mixed) garden beds all over the world.
Although some species of penstemons have relatively long life-spans, most garden writers especially in Britain suggest they should be treated as short-lived perennials. Christopher Lloyd's Garden Flowers (Portland Oregon; Timber Press, 2005) suggests, for example, that 'even if they survive several winters, [popular penstemon hybrids] are best replaced with young stock frequently' (p.278). The useful and interesting Gardener's Guide to Growing Penstemons (Newton Abbot; David & Charles, 1998) puts the period of replacement in Australia - said by its authors David Way and Peter James to have an ideal climate for growing penstemon hybrids - at around three years although they add that the decision to replace a plant should ultimately be judged by 'the vigour [or not] of basal growth' (p.35).
Other useful advice on penstemons provided by Way and James includes: