How to grow penstemons
All you need to know about planting and caring for penstemons, in our detailed Grow Guide.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Plant | yes | yes | yes | yes | yes | |||||||
| Flowers | yes | yes | yes | yes | yes | |||||||
| Cut back | yes | yes |
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 similar to those of a foxglove.
To add instant colour to your border in late summer, 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 free-draining 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.
Read on to learn more about how to grow penstemons in our comprehensive guide, below.
Where to grow penstemons
Penstemons are perfect for growing in the middle of a mixed border. They do best in a fertile, reasonably moist, free-draining soil. A position in full sun or light shade is ideal.
How to plant penstemons
Plant penstemons in spring so that new plants become established before having to face the winter. The stems are strong, so it's only in very exposed gardens 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. Take 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 the video below to see Monty Don demonstrate how to take penstemon cuttings, in this clip from BBC Gardeners' World:
Place your penstemon cuttings in a sheltered spot in the garden or a cold frame. They should 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 prune penstemons until spring. A typical problem with failing penstemons is the soil being waterlogged. Dig in horticultural grit to improve drainage.
How to care for penstemons
In spring, apply a general-purpose fertiliser to borders containing penstemons. Water freshly planted penstemons for the first summer to help them establish if they are planted in dry soil.
In autumn, cut back 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 before buying
- Always check plants for signs of damage or disease before buying
Where to buy penstemons
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 x Spread 90cm x 30cm
- Penstemon ‘Raven’ – dark-maroon flowers from June to October. H x S 1m x 30cm
- Penstemon ‘Sour Grapes’ (pictured) – almost aluminous deep-purple flowers from June to October. H x S 60cm x 45cm
- Penstemon ‘Osprey’ – pink and white flowers from June to October. H x S 90cm x 60cm
- Penstemon linarioides subsp. sileri – bright-yellow flowers on a lower growing plant. A half-hardy type for the front of a border, with flowers in July and August. Not widely available. H x S 1m x 45cm
Frequently asked questions
Should I deadhead my penstemon?
Penstemons benefit from being deadheaded, which helps promote new flower growth and keeps the plant flowering for longer. Simply remove whole flower spikes as the blooms fade and new ones will grow from the base.
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 No.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.
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