How to grow crocosmias
All you need to know about growing crocosmia, in this detailed Grow Guide.
Crocosmias provide a burst of colour late in the season, when most other flowering plants have faded. There are hundreds of crocosmia varieties to choose from, flowering in red, orange or yellow from June to late summer, above ornamental, strappy, bright green leaves. They make an excellent cut flower.
Crocosmias are also known as montbretia, although this tends to refer to the common species Crocosmia x crocosmiiflora. This has naturalised in many areas and is considered to be invasive. The cultivated varieties are less likely to become invasive.
How to grow crocosmia
Grow crocosmia in moist but well-drained soil in full sun to partial shade. Divide congested clumps every three to five years to rejuvenate them and encourage better flowering. In colder regions you may need to mulch the corms to protect them from frost.
More on growing crocosmia:
- When can I split crocosmia corms?
- Crocosmia, penstemon and rudbeckia pot display
- Crocosmia 'Paul's Best Yellow'
Find out all you need to know about growing crocosmia, below.
Where to grow crocosmias
Crocosmias are South African in origin, and require fertile, moist but well-drained soil. They thrive in full sun, but will tolerate light shade. In colder regions, choose a sheltered site.
How to plant crocosmias
Crocosmias grow from corms and can be planted like bulbs. Dig a generous hole, about 7-10cm deep and add a spadeful of well-rotted compost or other organic matter. Plant a handful of corms a few centimetres apart so you start out with a reasonable clump, and cover with soil.
Caring for crocosmias
In dry summers you may need to water clumps, and mulch in autumn to protect the corms from frost. Crocosmia corms multiply readily, so clumps will become congested and flower less vigorously over time. The best time to divide and replant congested clumps is in spring.
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How to propagate crocosmias
Crocosmia corms multiply over the years, forming new corms which grow on top of each other in a 'conjoined string'. To propagate crocosmia, lift clumps in spring and gently pull the corms apart. Plant up the top two corms from each string, which will be the newest and therefore make the most vigorous plants.
Watch our Quick Tips video with Daniel Haynes, gardenersworld.com, who explains how and when to divide crocosmia corms:
Growing crocosmias: problem-solving
Crocosmias can succumb to red spider mite, but are otherwise generally pest and disease-free. Some varieties can be too vigorous and may become invasive. Keep an eye on them and be vigilant – digging up and destroying the corms is the best way to deal with any invasive clumps. This may take several attempts.
Advice on buying crocosmias
- Choose widely - remember that the species, Crocosmia x crocosmiiflora, can be quite invasive and difficult to eradicate once established
- Choose a colour that suits the palette of your garden at the time of flowering (late summer to autumn)
- Check corms for signs of mould or damage before buying or planting
Where to buy crocosmia
Crocosmia varieties to grow
- 'Emily McKenzie' – a compact crocosmia. The bright orange flowers have an attractive mahogany throat. Foliage is a slightly darker green and it can be slightly less hardy than other varieties
- 'Citronella' – with upright, fresh green leaves and small, soft yellow luminous flowers
- 'Hellfire' – bears tight clusters of enormous, bright crimson flowers from mid-summer to autumn
- 'Lucifer' – with tall, arching sprays of intense, fiery red blooms. The first true red cultivar, ‘Lucifer’ is one of the tallest varieties growing up to 1.5m. The pleated leaves are also attractive in their own right and the seedheads can look decorative if left
- 'Harvest Sun' – a relatively new hybrid, bearing large orange-red flowers in contrast with upright, fresh green foliage
- 'George Davison' – at 60cm, this medium height crocosmia bears upright stems of golden yellow, freesia-like flowers from late-summer to autumn