I’ve been out to Green Jjam Nurseries to find out more about growing penstemon
There are so many reasons why I like penstemon. They’re the sort of plants that largely look after themselves, come in a wide range of colours and can flower from mid-summer to autumn. Best of all, at least in my mollusc infested garden, slugs and snails ignore them.
Their blast of late summer colour was obvious looking around Green Jjam Nurseries near Evesham.
The sales benches and stock plant area were a mass of pink, red, purple, white and mauve, with plants ranging from dainty and compact to 1.2m monsters that would hold their own in any border.
The nursery, run by Julia Mitchell, specialises in penstemon and has more than 120 different varieties. It’s an interest that started when she gave a home to Pershore College’s National Collection of pre-1995 penstemon cultivars during building work at the college. As a thank you, she was allowed to keep some of the plants she had propagated when the penstemon returned to Pershore and her collection began.
To those early varieties, she has added newer cultivars, although they have to be ‘good doers’ to be included.
“I find some of the new ones are not as hardy and not as good year on year.”
What she looks for are plants that are resistant to mildew – one of the few penstemon woes – and will regularly flower well.
Tips for growing penstemon
Successful growing, says Julia, comes from following a few simple rules.
The most important thing is position. Penstemon like full sun and need this to flower well.
Soil type is also key to success. They prefer well-drained soil but will tolerate heavy, wet ground, if it is improved with organic matter or grit before planting.
Plant them earlier in the season, if your soil isn’t ideal. Julia recommends May to August so that they have time to develop a good root system. If you acquire a penstemon any later than September, keep it in a pot outside against a house wall and plant out in the spring.
Buy from a reputable grower and beware of end-of-season sick-looking plants in garden centres to avoid importing eel worm into your garden.
“So long as you don’t buy it in, you will never have it.”
Never cut back a plant until spring and that’s not judged by the calendar but by when the plant has new shoots of about 8cm in length. Cut back all the old stems allowing room for the new shoots to grow.
Julia explains that leaving the top growth on will help to protect the plant over the winter.
“It’s not frost that’s an issue, it’s wet during the winter,” she says. “If you leave the leaves on, the roots have got something to do and won’t rot.”
She also dismisses the commonly held idea that narrow-leaved varieties are more frost hardy and believes it stems from two old varieties ‘Schoenholzer’ and ‘Andenken an Friedrich Hahn’, which were renamed ‘Firebird’ and ‘Garnet’ in the UK.
“Both have got thin leaves and both are very tolerant of wet soil, which means they last year to year even if they’re cut back.”
Cutting back in spring is important though to stop the plants becoming woody, which will affect how well they flower.
Deadheading is vital, if you want to get the longest flower season. Cut the flower spike back to a healthy pair of leaves and side shoots.
You shouldn’t need to feed them and don’t need to worry about vine weevil as, like the slugs, they ignore penstemon.
Penstemon are easy to propagate from cuttings – Julia raises about 4,000 a year – and August and September are the time to do it.
She takes a healthy 7cm piece, cut just below a leaf node. Half of the leaves from the bottom are taken off, leaving a couple of pairs of leaves.
The cuttings are put into seed and potting compost – Julia makes her own but a good brand would be ideal. The cuttings are kept moist until they root and then kept drier.
Julia’s top penstemon picks
‘King George V’ – a really good old variety with red blooms. It’s a strong grower and flowers well.
‘Blackbird’ – a slender plant that gets to about 1.2m with purple flowers.
‘Pensham Czar’ – another purple but with paler blooms that are lilac-purple.
‘Suttons Pink Bedder’ – an old variety, it has pure mid-pink blooms with a white throat and shiny foliage.
‘White Bedder’ – this may have a slightly sprawling habit but it’s made up for by pure white flowers that are blush pink in bud. It can take a while to get established but is worth the effort.
Green Jjam Nurseries will be at the Malvern Autumn Show on September 28 and 29. For more details about the nursery, visit the website.
You can read about more of my nursery visits here.
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Do penstemons do well in pots?
I’ve checked with Green Jjam and the advice is it depends on the variety. The volacano series was bred to be grown in pots.