How to grow gunnera
Find out all you need to know about growing gunnera, in this detailed Grow Guide.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Plant | yes | yes | ||||||||||
| Flowers | yes | yes | yes | |||||||||
| Cut Back | yes | |||||||||||
| Collect Seeds | yes | yes |
Plant Size: Height: 250 Spread: 400 |
With their large, umbrella-like leaves, gunneras are some of the largest and most impressive plants that have historically been grown in the UK. At 2.5m high and 4m wide, the best-known gunnera, Gunnera manicata, has huge leaves that can reach 2m wide. However, a study conducted by the Royal Horticultural Society has found that Gunnera manicata was actually lost to cultivation soon after it was introduced and that plants thought to be Gunnera manicata are actually a hybrid of Gunnera manicata and the invasive Gunnera tinctoria. This hybrid has now been named Gunnera × cryptica.
Sales of Gunnera tinctoria and Gunnera manicata / Gunnera × cryptica are banned. Gardeners already growing these giant gunneras must ensure they don't let them spread beyond their gardens. Small gunneras, such as Gunnera magellanica and Gunnera perpensa, are not banned and are still legal to buy and grow in gardens. There are also larger gunneras that are not considered invasive, such as Gunnera insignis and Gunnera killipiana, but these plants are not hardy in most areas of the UK and are not widely available.
If you have a giant gunnera in your garden and would like to remove it, the best thing to do is cut it back completely and then dig it out. Alternatively, to stop it spreading, simply cut flowerheads in summer before they set seed, and burn them on site or take them to an authorised landfill site or other suitable disposal site.
For a similar dramatic effect to gunnera, we recommend Rheum palmatum and Crambe cordifolia, which are not considered invasive.
How to grow compact gunneras
Grow small gunneras in very moist, humus-rich soil in a sheltered spot in full sun to partial shade.
Where to plant gunnera
Grow compact gunneras in permanently damp, humus-rich soil in a sheltered spot in full sun to partial shade, such as the edge of a pond. Small gunnera species are also suitable for pots as long as compost remains moist.
How to plant gunnera
Buy a plant and dig a hole, adding in some well-rotted compost. Place gunnera in the hole and firm in gently. Water well and ensure the soil remains moist.
Caring for gunnera
Gunneras are herbaceous perennials so the spectacular foliage will die back at the end of the summer. They may need protection from frost damage over winter. Gunneras in containers are best placed in a frost-free spot over winter.
Propagating gunnera
Compact gunneras can be divided in spring.
Pests and diseases
Gunneras are generally pest and disease free. Brown leaves and dieback in spring can be due to frost but the plant should bounce back, producing new growth.
Advice for buying gunnera
- Check that you have the right conditions – gunneras need permanently moist soil
- Also check the hardiness of the species you buy to ensure it is suitable for your area
- Plants may need protection from frost over winter
Where to buy small gunneras online
Gunnera varieties to try
- Gunnera perpensa - a South African variety, known as river pumpkin, that is hardy in the UK. The leaves have a light mottled pattern and a purple flower spike appears in late summer. Height x Spread: 75cm x 75cm
- Gunnera magellanica (devil's strawberry) - a dwarf, spreading variety with leaves that look like miniature versions of the giant varieties. It makes excellent ground cover in damp, boggy soil and is hardy to around -10°C. H x S: 15cm x 30cm
- Gunnera prorepens - this compact gunnera species from New Zealand has attractive bright red fruiting spikes in autumn. H x S: 10cm x 40cm
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