How to grow ranunculus
Ranunculus range from hardy, low growing perennials, useful in borders or meadows, to buttercups that thrive on the edge of ponds and streams. The satin-like petals of Persian buttercups are ideal in containers and as bedding plants but like alpine ranunculus, benefit from specialist care to flower well.
- Prefer moist soils that don’t dry out
- Flower in spring and early summer
- Buttercups will not flower in deep shade
- Meadow and bog buttercups are an early source of nectar
- Persian buttercups (Ranunculus asiaticus) are good cut flowers
- Creeping buttercup (Ranunculus repens) can be a weed
- Contact with the sap may irritate the skin
All you need to know
Choosing a ranunculus
Choose a ranunculus that fits best with the growing conditions in your garden. Here are some ranunculus for specific sites and conditions:-
Moist, partial shade: use hardy, low-growing Ficaria verna that are closely related to Ranunculus, and flower in spring, dying down in summer to make space for other border plants. Lesser celadine (Ficaria verna subsp. verna) can spread as a weed in gardens but is a good early source of nectar in wildlife gardens.
Moist borders in sun: use double-flowered, clump-forming perennial ranunculus such as Ranunculus acris 'Flore Pleno' (d) and Ranunculus aconitifolius 'Flore Pleno' (d) for greatest impact.
Moist wild flower meadow: buttercups suitable for introducing into damp meadows include the native perennial meadow buttercup (Ranunculus acris), and bulbous buttercup (Ranunculus bulbosus). If sowing a cornfield annuals mix, include corn buttercup (Ranunculus avensis). These buttercups provide an early source of nectar for pollinators as do many other British wildflowers.
Ponds and streams: aquatic or bog buttercups are best grown in the mud at the edge of a pond or stream. Water crowfoot (Ranunculus aquatilis) prefers a depth 15-60cm (6in-2ft) of still or fast moving water, while lesser spearwort (Ranunculus flammula) and greater spearwort (Ranunculus lingua) prefer 15-22cm (6-9in) of still or slow moving water. These British wildflowers are good for pollinators.
Bedding and pot plants: Persian buttercups (Ranunculus asiaticus) come in the widest range of flower colours for pots, bedding or as cut flowers.
Alpine ranunculus: if you have a rockery or alpine glasshouse, try growing Ranunculus alpestris, Ranunculus calandriniodes, Ranunculus amplexicaulis and Ranunculus glacialis.
Choose a ranunculus that has received the RHS Award of Garden Merit as it has been tested and perfoms well in the garden.
- Buy border ranunculus as pot grown plants, ideally in spring from garden centres or mail order
- Buttercups for wild flower meadows are available as seed and plug plants in spring by mail order. A limited range of seed is available by mail order from specialist suppliers of wildflower seed
- Buttercups for ponds and streams can be purchased as pot grown plants from specialist aquatic nurseries or by mail order, while seed is available from specialist suppliers of wildflower seed online
- Persian buttercups can be purchased as tubers, available in autumn or spring, or as young plants in spring from garden centres or by mail order. Seed is available by mail order but they are more easily grown from tubers or young plants
- Alpine buttercups are available as pot grown plants from specialist alpine nurseries directly or by mail order
Grow hardy perennial ranunculus in any damp, garden soil that does not dry out, in sun or partial shade. Avoid planting in deep shade as they will not flower.
In borders, meadows, ponds and streams margins
Ideally, plant your plug plants or container grown ranunculus in spring, at the same depth they are in the pot. Sow seed for meadows during March and April or in September depending on the soil conditions. On lighter soils, autumn sowing allows the plants to germinate and establish quickly although some seed may only germinate in the spring. On heavier, water logged soils the seedlings or seed may rot in winter.
Bedding and pot ranunculus
Soak the tubers of Persian buttercups (Ranunculus asiaticus) for a day, before planting. Then plant in containers from September to December with a loam-based compost with 20% added horticultural grit, to improve drainage and incorporate a slow-release fertiliser like Growmore. Place the tubers with the claws downwards, 10cm (4in) apart and cover with 5cm (2in) compost.
Grow on in bright light, in a cool greenhouse or cold frame, with good air flow to prevent grey mould and aphids. Established plants can tolerate temperatures down to 0°C (32°F). Growing plants under cool conditions (below 15°C (59°F)) produces compact plants and delays flowering until April. Plants can be placed outside when all danger of frost has passed.
For outdoor flowering in autumn, plant tubers directly in the border up to June. Select a sunny spot with free-draining soil and add well-rotted compost, to help retain moisture.
These plants need gritty, humus-rich well-drained soils, in full sun and grow well in a scree bed or alpine house. When growing in pots, use a compost with equal parts loam, grit and leaf mould. These hardy plants may be short lived.
- Water seedlings and young plants regularly, ensuring the top 15cm (6in) of soil is damp but not soggy, in the first few months
- Keep plants moist when growing and flowering
- Feed border plants in spring when they start to grow with a balanced fertlilser, such as Growmore or bonemeal (70g per sq m or 2oz per sq yd)
- Plants growing in meadows, along edges of ponds and streams do not need feeding
- Remove flowers on alpine and border plants to encourage further flowering
- If growing Persian buttercups (Ranunculus asiaticus) for the vase, cut the stems before the flowers are fully open and they should last 10-12 days
- Most ranunculus are hardy so don't need any special care over winter
- Grow Persian buttercups (Ranunculus asiaticus) in a cool greenhouse in winter
Caring for older plants
- Some spring flowering plants such as Ranunculus repens and Ficaria spread rapidly and can become a nuisance
- Early flowering Ficaria die down in summer, so place the plant label under the plant. This way you can identify the plant if you dig it up by mistake
- Percian buttercups (Ranunculus asiaticus) are best grown as an annual and replaced every year
- Spring flowering perennials such as Fricaria, that die down in summer, are best split after flowering
- Summer flowering perennial ranunculus can be divided in autumn or spring. Many naturally increase from seed but division is quicker
- If growing Persian buttercups (Ranunculus asiaticus) from seed rather than tubers, sow in plug cells in September, cover the seed lightly and maintain at 15°C (59°F). Keep moist and frost-free during winter, potting into the final pots when they have four true leaves. Plants may flower in their first year before dying down
- In most other species, dormancy needs to be broken by exposure to winter cold. Harvest the seed when ripe but still green in spring and sow immediately, in pots. Use a gritty, loam-based compost. Expose the pots to the winter cold but keep them in a sheltered place such as a cold frame. Fresh seed often germinates in the following spring but older seed (black or brown seed) may take one to two years to germinate
- Aquatic ranunculus such as water crowfoot (Ranunculus aquatilis) and greater spearwort (Ranunculus lingua) can be divided in spring or late summer and cuttings taken after flowering. Alternatively sow seeds fresh and keep at 10°C (50°F)
Ranunculus are generally trouble free but can suffer from powdery mildew in dry conditions. Maintain good air circulation when growing plants in cold frames and greenhouses to prevent problems with grey mould and aphids.
Some ranunculus can spread rapidly and may need to be reduced. Lesser celandine can be especially problematic.
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