Crimson flowers of penstemon 'Razzle Dazzle'

How to grow penstemons

All you need to know about planting and caring for penstemons, in our detailed Grow Guide.

A table displaying which months are best to sow, plant and harvest.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Plant
Plant

Do not Plant in January

Do not Plant in February

Do Plant in March

Do Plant in April

Do Plant in May

Do Plant in June

Do Plant in July

Do not Plant in August

Do not Plant in September

Do not Plant in October

Do not Plant in November

Do not Plant in December

Flowers
Flowers

Plant does not flower in January

Plant does not flower in February

Plant does not flower in March

Plant does not flower in April

Plant does not flower in May

Plant does flower in June

Plant does flower in July

Plant does flower in August

Plant does flower in September

Plant does flower in October

Plant does not flower in November

Plant does not flower in December

Cut back
Cut back

Do not Cut back in January

Do not Cut back in February

Do not Cut back in March

Do Cut back in April

Do Cut back in May

Do not Cut back in June

Do not Cut back in July

Do not Cut back in August

Do not Cut back in September

Do not Cut back in October

Do not Cut back in November

Do not Cut back in December

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.

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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, don’t cut back plants until spring. 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 'MacPenny's 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

Purple-blue penstemon 'Catherine-De-La-Mare'
Purple-blue 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 garden 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 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:

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

Topping a pot of newly-planted penstemon cuttings with gravel
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 cut faded stems back hard until spring.

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


How to care for penstemons

White and purple-pink flowers of 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.

Deep-purple flowers of penstemon ' Sour Grapes'
Deep-purple flowers of penstemon ‘ Sour Grapes’

Great penstemon varieties to grow

  • Penstemon ‘Raven’ – dark maroon flowers from June to October. Reaches a height of 100cm
  • Penstemon ‘Sour Grapes’ (pictured) – stunning, almost aluminous pale purple flowers from June to October. Reaches a height of 60cm
  • Penstemon ‘Osprey’ – pink and white flowers from June to October. Height of 90cm
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  • 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