How to grow penstemons

Crimson flowers of penstemon 'Razzle Dazzle'

Penstemons are valuable garden plants, grown for their long-flowering season and popularity with bees. There are many different types of penstemon, with some suited to the alpine garden while the majority are at home in the heart of a herbaceous border. Border penstemons have tubular late summer flowers in a wide range of colours. The flowers look very similar to those of a foxglove.

If you’re looking at your border in late summer and need to add some instant colour, penstemons are the answer. Plant in groups of three or five for impact. Most border penstemons will continue to flower up until the first frosts.

How to grow penstemons

Grow penstemons in moist but well-drained soil in full sun to partial shade. Mulch annually with well-rotted manure or leaf mould, and feed weekly in summer. Penstemons are short-lived perennials that can suffer in winter. To avoid losses, pruning penstemon is best done in spring. It’s also a good idea to take summer cuttings to prevent winter losses.

More on growing penstemons:

Learn how to grow penstemons in our comprehensive guide, below.


Where to grow penstemons

Penstemon MacPennys Pink
Penstemon ‘MacPenny’s Pink’

Border penstemons are perfect for growing in the middle of a mixed border. They do best in a fertile, reasonably moist soil that is free-draining. Full sun or light shade is ideal.


How to plant penstemons

Penstemon 'Catherine de la Mare'
Purple penstemon ‘Catherine-De-La-Mare’

Plant penstemons in spring so that new plants get a foothold before having to face the winter. Stems are strong so it’s only in very exposed gardens that plant supports will be required.


How to propagate penstemons

Taking penstemon cuttings
Taking penstemon cuttings

Take penstemon cuttings from late summer to early autumn. Select soft growth without a flower. Cut each cutting back to below a leaf joint and remove the lower penstemon leaves. More than one cutting can be put into a pot of cutting compost as long as the leaves don’t touch.

Watch as Monty Don demonstrates how to take penstemon cuttings, in this clip from Gardeners’ World:

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Place your penstemon cuttings in a sheltered spot in the garden or a cold frame. All being well they’ll be ready to plant out the following May.


Growing penstemons: problem solving

Potted penstemon cuttings
Topping a pot of newly-planted penstemon cuttings with gravel

Penstemons are fairly short-lived plants. Take cuttings of your favourite penstemons every few years to ensure you have the next generation in place.

To prevent plants from failing to make it through winter, don’t prune penstemons until spring.

If you continue to fail with penstemons ensure the soil is not waterlogged. Dig in horticultural grit to improve drainage.


How to care for penstemons

Penstemon 'Laura'
White and purple-pink flowers of penstemon Laura’

In spring apply a general purpose fertiliser to your mixed borders. Water freshly planted penstemons for the first summer to help them establish on a dry soil.

In autumn cut back the faded foliage by just a third to prevent windrock and then cut the remaining foliage back hard in spring after the last frost.


Advice on buying penstemons

  • Penstemons come in a range of flower colours and heights – make sure you have the right choice for your garden
  • Always check plants for signs of damage or disease, before buying

Where to buy penstemons

Great penstemon varieties to grow

Penstemon 'Sour Grapes'
Deep-purple penstemon ‘ Sour Grapes’
  • Penstemon ‘Raven’ – dark maroon flowers from June to October. Reaches a height of 100cm
  • Penstemon ‘Sour Grapes’ (pictured) – stunning, almost aluminous deep purple penstemon flowers from June to October. Reaches a height of 60cm
  • Penstemon ‘Osprey’ – pink and white flowers from June to October. Height of 90cm
  • Penstemon linarioides subsp. sileri – bright yellow flowers on a lower growing plant of only 45cm. A half-hardy type for the front of a border with flowers in July and August. Not widely available

Frequently asked questions

How should I deadhead my penstemon?

Penstemons benefit from being deadheaded, which helps promote new flower growth, and keeps your penstemon flowering for longer. Simply remove whole flower spikes as the blooms fade.

Can I grow penstemon in a pot?

Penstemons have quite deep roots, so need to be grown in a large pot, ideally with a height and width of 45cm. Choose a peat-free, soil-based compost such as John Innes Number 3, and keep the pot well watered but allow the water to drain. In summer, feed weekly with a liquid plant food, to boost flower production.

Carts

Accessories

Flower Seeds

Composting

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