Buttercups: ranunculus from tubers, creeping buttercup in the lawn and toxicity

In brief: The garden Persian buttercup (ranunculus) grows from claw-shaped tubers that do not overwinter outdoors here. Soak the tubers for a few hours, start them in February to March in a cool bright room, claws down, 5 cm below the surface, and put them outdoors after mid May. Wild buttercups are poisonous and irritate the skin.

The word buttercup covers two completely different plants. For some it is a luxury cut flower with full, rose-like blooms that the florist sells as ranunculus. For others it is a yellow weed that creeps through the bed and lawn and cannot be pulled out.

We devote most of the article to growing the garden ranunculus from tubers, because it is in autumn that the tubers start to be sold and people wonder what to do with them until spring. At the end you will also find how to deal with creeping buttercup in a lawn and why wild buttercups are poisonous.

Which buttercup are you looking for

You recognise the garden ranunculus by its full layered flowers in white, pink, apricot, red or yellow and by tubers that look like a small dry spider or a claw. Wild buttercups have simple glossy yellow flowers with five petals.

Tubers bought in autumn: what to do with them until spring

Ranunculus tubers are sold in autumn and in spring. In the Mediterranean they are planted in autumn and flower early in spring. In the Czech climate the outdoor winter would kill them, so an autumn purchase gives you two options:

• Store until February. Leave the dry tubers in a paper bag or box in a dry, cool place where it does not freeze. Check once a month that they are not going mouldy.
• Plant in containers at once. Only if you have an unheated greenhouse, a cold frame or a bright room where the temperature does not fall below 0 °C and does not exceed 15 °C. The plants will then flower as early as April.

Ranunculus does not belong on a windowsill in a warm flat. At a temperature above 15 °C and in dim light it becomes leggy and does not flower.

Starting the tubers step by step

1. In February or at the beginning of March immerse the tubers in lukewarm water for a few hours, at most overnight. They swell to roughly double their size.
2. Prepare pots or seed trays with a free-draining substrate. Mix about a fifth of perlite or coarse sand into ordinary substrate.
3. Lay the tubers claws down, 10 cm apart, and cover with 5 cm of substrate.
4. Water once, and then keep the substrate only slightly moist. In wet conditions the tubers rot before they sprout.
5. Put the containers in a bright place at 10–15 °C, for example in a cool room, on a glazed veranda or in a cold frame.
6. After sprouting, water regularly but without overwatering. Cool keeps the plants compact.
7. After mid May, when frosts are no longer a threat, harden the plants off and plant them outdoors.

Anyone without a cool bright place can plant the tubers straight outdoors at the end of April or in May. The plants then flower later, usually in summer. More tips on starting flowers early in spring can be found in the article what to sow in February.

Ranunculus in a bed, on a balcony and in a vase

Outdoors it needs a sunny spot and free-draining, nutritious soil that neither dries out nor stands in water. For containers choose pots with holes in the bottom and a drainage layer. On a balcony ranunculus flowers with other spring and summer flowers; inspiration for combinations is in the article balcony plants that will flower until autumn.

• Support taller varieties with a stake before the wind breaks them.
• During growth feed once every 2 weeks with a fertiliser for flowering plants.
• Remove spent flowers; the plant then sets further buds.
• For the vase cut when the buds are coloured and soft to the touch but not yet open. Such flowers last 10–12 days.

Advice on keeping cut flowers fresh longer can be found in the article how to keep plants beautiful in a vase for a long time.

After flowering: dig up or buy new?

When the leaves turn yellow in summer, the plant goes into dormancy. Carefully lift the tubers, clean off the soil and leave them to dry for a few days in the shade. Then store them in a paper bag in a dry, cool place where it does not freeze, and repeat the procedure in February.

Stored tubers, however, often flower more weakly than new ones, especially if the plant suffered from heat over the summer. Many growers therefore treat ranunculus as a seasonal flower and renew the tubers every year. It is worth keeping mainly large, firm tubers from plants that flowered well.

Creeping buttercup in a lawn and beds

Creeping buttercup forms long runners that root at the nodes and a dense network of roots. It does best in compacted and damp soil, where grass weakens. At the same time it is a valuable plant for bumblebees and bees, so in a wild part of the garden feel free to leave it.

• In a bed: lift the plants with a digging fork together with the roots and runners. A remnant of a runner is enough and the plant returns. After clearing, mulch the bed.
• In a lawn: dig out individual clumps with a weed puller. In spring and autumn aerate and feed the lawn; dense grass gradually pushes the buttercup out.
• The cause: if creeping buttercup spreads over a large area, deal with the drainage. In a wet and compacted spot it comes back even if you pull it out.

How to renew a lawn and make it denser is described in the article spring lawn crash course.

Why animals leave buttercups standing in a pasture

Buttercups contain ranunculin, from which protoanemonin is formed when the plant is damaged. It irritates skin, eyes and mucous membranes. Grazing animals avoid fresh buttercups, because they burn. When dried, this substance breaks down, which is why buttercup in hay does not harm animals as fresh buttercup does.

• Skin: the sap from crushed leaves and stems can cause redness and blisters. Wear gloves when pulling out buttercups and when cutting ranunculus.
• Dogs and cats: after chewing there is a risk of vomiting, diarrhoea, drooling, ulcers in the mouth and a staggering gait. Contact a vet.
• Children: flowers or leaves in the mouth burn and irritate. If a child has eaten the plant, call the Toxicological Information Centre on 224 919 293 or 224 915 402.

Ranunculus illyricus and greater spearwort are, under Annex II of Decree 395/1992 Coll., highly endangered species. Do not pick or dig them up in the wild.

Frequently asked questions

When should I plant buttercup tubers?

In February to March into containers in a cool bright room, outdoors after mid May. You can plant straight into a bed at the end of April and in May; the plants then flower in summer.

Which way up do ranunculus tubers go?

The claws point down and the smoother upper part up. The tubers are covered with about 5 cm of substrate.

Does Persian buttercup overwinter outdoors?

No. It tolerates only temperatures around zero. The tubers have to be dug up in summer and stored dry where it does not freeze, or planted in autumn in containers in an unheated but frost-free space.

Is buttercup poisonous?

Yes. Fresh buttercups contain protoanemonin, which irritates skin and mucous membranes. They are poisonous to dogs, cats and horses, and after chewing vomiting, drooling and ulcers in the mouth appear.

How do I get rid of creeping buttercup in a lawn?

Dig out the clumps with their runners, aerate the lawn and feed it so that it thickens. In a permanently wet and compacted spot only improving the drainage helps.

Recommended products

We currently do not have ranunculus tubers on offer. The following suit starting them early and growing in containers:

• FORESTINA DEKOR perlite 2–4 mm, 2.5 l – a fifth of perlite in the substrate prevents the overwatering to which the tubers are most sensitive.
• CAMPANULA flower pot, 23×17 cm – for three to five tubers on a balcony, with holes for drainage.
• PREMIUM VCD flower pot, 13 cm diameter – for starting individual tubers early; the plants are then transplanted without root damage.

Sources

• Royal Horticultural Society: How to grow ranunculus
• Royal Horticultural Society: Creeping buttercup
• ASPCA Animal Poison Control: Buttercup (Ranunculus spp.)
• Decree No. 395/1992 Coll., Annex II: list of specially protected plant species

Updated: 27 September 2026