Gardens Illustrated
Penstemon
© Jason Ingram

Penstemon: how to grow, plus 16 of the best varieties

Published: April 29, 2022 at 2:19 pm

Penstemon is a plant that is easy to grow and propagate, is not susceptible to pests and diseases and has brightly coloured flowers for months on end. Plantsman John Hoyland is your guide to this adaptable plant, and recommends 16 of his favourite varieties to grow. Photographs Jason Ingram

Few herbaceous perennials are as generous as penstemons. Many start flowering in midsummer and, long after other plants are exhausted, will carry the garden on until the first frosts. So long flowering and floriferous are they that they were used as bedding plants by the Victorians, who planted up whole borders with them to fill the garden with summer colour. Margery Fish, a gardener and writer in the middle of the 20th century, admitted to forever ‘preaching the benefits of Penstemon for continual colour’.

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Plant breeders in the UK and North America have recently rediscovered the virtues of penstemons and the past decade has seen lots of new introductions. All the modern forms keep the characteristic tubular colourful flowers that give easy access to bees and butterflies.

IN BRIEF

What A genus of about 250 species of semi-evergreen and deciduous perennials grown for their profusion of flamboyant flowers.

Origins Most are native to North America.

Season The main flowering period is early summer to mid-autumn.

Size From 15cm to 1m tall.

Conditions An undemanding and adaptable plant that grows best in well-drained soil in a sunny situation.

Hardiness Very hardy to frost hardy.

Penstemon is the largest family of flowering plants endemic to North America with about 250 species found in habitats ranging from forests to alpine meadows and prairies. Some are small, low-growing plants suitable for rock gardens and alpine houses and some are taller, more floriferous forms which appeal to modern gardeners. Most of the new hybrids are descended from just a handful of species, mainly Penstemon hartwegii, a semi-evergreen species from Mexico.

Despite there being so many garden forms of Penstemon already available, plants breeders are starting to mine the potential that other species may offer in creating new hybrids. The resurgence in popularity of Penstemon looks to be fuelled by new forms and new colours, which will hopefully secure the plant’s place in our garden palette.

How to grow pentsemon

Where to grow pentsemon

Except in very cold or very wet gardens, penstemons should be easy to grow throughout the UK. They are at their happiest basking in a sunny situation in well-drained soil. Give them plenty of room to grow where they are not crowded out by other plants.

How to care for pentsemon

Regularly cutting down old flower spikes during the summer will prolong flowering and help keep the plant vigorous. After a couple of years plants often become woody and straggly, so need pruning to keep them in shape and to produce new growth. They are not susceptible to specific pests or diseases and often appear in lists of plants that deer and rabbits avoid. Treat that advice with scepticism if your garden is visited by either of these animals and try a couple of plants before investing in what might turn out to be deer or rabbit food.

Producing as many flowers as most penstemons do take a lot of energy, so add compost to the soil when planting. Mulching around the plant in the autumn will feed the soil and also help protect the base of the plant from frosts.

Penstemons with narrow leaves tend to be the hardiest. In general, the broader and fatter the leaves, the more tender the plant. As an insurance against cold or wet winter it is advisable to take cuttings of tender penstemons.

How to take penstemon cuttings

Taking cuttings of penstemons is easy, and if you are new to taking cuttings penstemons are good plants to start with. The cuttings don’t require any special equipment other than a cool, light, airy and frost-free place to keep them in over winter.

Take the cuttings between mid-July and mid-September. Fill a 9cm pot with cutting compost or a 50:50 mix of compost and grit. Collect 10-12cm-long tips of a shoots that do not have flowers. Make the cut with sharp secateurs or a sharp knife just below where the leaves join the stem. Remove the leaves from the bottom half of the cuttings. Cut off the top third of the remaining leaves – this looks drastic but will reduce the amount of moisture the cutting loses. Insert the cutting to about two-thirds of its depth. You should get four or five cuttings into a 9cm pot. Water the pot and keep it in a cool place away from direct sunlight. Keep the compost moist but not wet. In a couple of weeks the cutting will have rooted. You can either pot up the young plants immediately or in the following spring. Both cuttings and newly potted young pants should be kept away from frosts.

Penstemon ‘Blueberry Taffy’

Penstemon
Penstemon 'Blueberry Taffy' © Jason Ingram

A floriferous cultivar that is part of a series recently selected by Terra Nova Nursery in the USA for their upright, bushy habit and long flowering period. The vivid flowers first appear in June and continue until the first frosts. 45cm

Penstemon ‘Cha Cha Lavender’

Penstemon
Penstemon 'Cha Cha Lavender' © Jason Ingram

One of the Cha Cha Series of penstemons that were bred to maintain a compact habit throughout a long flowering period. On this selection the flowers are densely packed along the stem. 50cm

Penstemon ‘Willy’s Purple’

Penstemon
Penstemon 'Willy's Purple' © Jason Ingram

An imposing plant with flowers that are a dark wine colour and have a waxy appearance. It was first found growing in a garden in New South Wales, Australia and has been taken up by American and European nurseries. 1.2m

Penstemon ‘Cherry’

Penstemon
Penstemon 'Cherry' © Jason Ingram

One of many selections with vibrant red flowers. Here the large blooms have red stripes on a white background in the throat of the flowers. It is a vigorous plant in its first couple of years but after that it will need replacing. 80cm

Penstemon ‘Knightwick’

Penstemon
Penstemon 'Knightwick' © Jason Ingram

Bred in Worcestershire in the early 1990s by Perhill Nursery, this is a floriferous and long-flowering hybrid that starts into flower in early June. The outer surface of the flower has a metallic sheen. It forms a rounded dome. 80cm

Penstemon Phoenix Violet (= ‘Pheni Vio’)

Penstemon
Penstemon 'Phoenix Violet © Jason Ingram

Bred by Jason Jandrew in the USA and released in 2006 as part of a series of relatively short plants with large, open flowers. On this selection the flowers are plum coloured with a clear white throat and begin to appear in early June. 50cm

Penstemon ‘Boysenberry Taffy’

Penstemon
Penstemon 'Boysenberry Taffy' © Jason Ingram

An upright plant with a bushy habit that begins flowering in June and, if deadheaded, will continue until the first frosts. The large flowers have a wide opening, perfect for fat bumblebees and are packed on flower-spikes. 25cm

Penstemon ‘Blackbird’

Penstemon
Penstemon 'Blackbird' © Jason Ingram

One of the Bird Series, this upright, semi-evergreen cultivar with thin, wiry stems and slender, reddish-purple flowers that have a white throat. It begins to flower in late July. The leaves are narrow, willow-like and will last through mild winters. 80cm

Penstemon ‘John Nash’

Penstemon
Penstemon 'John Nash' © Jason Ingram

Found growing in plantswoman Margery Fish’s famous garden at East Lambrook in Somerset. The flowers are a delicate, pale mauve with a pure-white interior. Similar to, but smaller and more compact than, the popular Penstemon ‘Alice Hindley’. 60cm

Penstemon heterophyllus ‘Blue Spring’

An evergreen cultivar with luminous, bright-blue flowers with a purple throat that in sunlight appears turquoise. The leaves are narrow and glossy with a glaucous sheen. It is a long-lived plant that flowers most in July and August. 45cm

Penstemon hartwegii Sensation mix

Penstemon
Penstemon hartwegii 'Sensation' © Jason Ingram

This is a seed strain of large-leaved, compact plants. The flowers are large in a range of pink and pale mauves with occasional plants having strong red or deep purple flowers. Sown early, they are often used as annuals. 60cm

Penstemon Phoenix Appleblossom (= ‘Pheni Ablos’)

Penstemon
Penstemon Phoenix Appleblossom © Jason Ingram

The short stems are packed with flowers that are deep red in bud and open to white with a delicate, pale-pink edging. A compact plant, part of a group bred in 2006 in the USA by Jason Jandrew. 50cm

Penstemon ‘Elgar Firefly’

Penstemon
Penstemon 'Elgar Firefly' © Jason Ingram

One of the Elgar Series, this cultivar is a sparsely flowered plant with a loose, open habit that is in flower from mid-June to the first frosts. The flowers are a pale raspberry colour with a pale throat and a velvety sheen on the outside of the petals. 60cm

Penstemon Fujiyama (= ‘Yayama’)

Penstemon
Penstemon 'Fujiyama' © Jason Ingram

A compact plant with an upright habit that was originally bred to be grown in patio containers. The large flowers are an attractive combination of a solid pink lip that fades to white at the base, and white throat with pink streaks. 60cm

Penstemon digitalis ‘Mystica’

Penstemon
Penstemon digitalis 'Mystica' © Jason Ingram

A seed strain widely used in the cut-flower industry. The foliage has a plum-coloured flush, most noticeable in spring, which contrasts with the dense lavender-pink flowerheads. It produces an abundance of flowers in late June and early July. 75cm

Penstemon ‘Osprey’

Penstemon
Penstemon 'Osprey' © Jason Ingram

A stately hybrid that has been popular since it was introduced in the 1960s. The fat flowers are a soft white with a pale-pink picotee edge. It is one of the Bird Series, a group of penstemons, raised in Evesham in Worcestershire and named after birds. 1m

Where to see and buy penstemon

Binny Plants, Binny Estate, Ecclesmachan Road, Uphall, West, Lothian EH52 6NL. Tel 01506 858931, binnyplants.com

Froggery Cottage, 85 Breakleys Road, Desborough, Northamptonshire NN14 2PT. froggerycottage.com. Open on selected dates.

Hardy’s Cottage, Garden Plants, Priory Lane Nursery, Freefolk Priors, Whitchurch, Hampshire RG28 7FA. Tel 01256 896533, hardysplants.co.uk

Hayloft Plants, The Pack House,, Manor Farm Nursery, Pensham, Pershore, Worcestershire WR10 3HB. Tel 01386 554440, hayloft.co.uk

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Pershore College, Avonbank, Pershore, Worcestershire WR10 3JP. Tel 01386 551149, wcg.ac.uk/plantcentre.

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