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, don’t cut back plants until spring. Take summer cuttings to prevent winter losses.
More on growing penstemons:
- How to take penstemon cuttings
- Best penstemons to grow
- Crocosmia, penstemon and rudbeckia pot display
Learn how to grow penstemons in our comprehensive guide, below.
Where to grow penstemons
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
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
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
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
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.
Great penstemon varieties to grow
- Penstemon ‘Andenken an Friedrich Hahn’ (formerly known as ‘Garnet’ ) – wonderful crimson flowers from June to September with narrow dark green leaves. Height 75cm
- 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
- 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