What is a Ranunculus and how do I get started?
The ranunculus grows from tubers that rest over the winter and come to life when conditions are right. Before planting, it is a good idea to soak the tubers in lukewarm water for a few hours so that they soften and begin to swell. Two to four hours is sufficient; if left longer, they risk starting to rot. Once the corms have soaked for a while, they absorb water and become plumper. They increase significantly in size and will take up much more space in the tray or pot than one might first imagine when seeing them dry. At Florea, we usually grow ranunculus in seed trays with slightly higher sides of 5–10 cm. The tubers are planted with the “claws” facing downwards, quite shallowly, so 3–5 cm deep is sufficient.
Once planted, the tray should be placed in a cool, dark spot. Four to ten degrees Celsius is optimal. If the temperature is higher, the leaves risk shooting up too quickly, and the plant will focus more on foliage growth than on developing strong roots. Don’t forget to check the tray now and then. If it is very dry, you can give a little water, but usually this is not necessary if the temperature is optimal. After about two weeks, the ranunculus tubers usually wake up and small white roots start to appear. Generally, the first shoots are also visible at this stage, which means it is time to plant them out.
Location, soil, and temperature
Choose a spot with plenty of light, preferably sun, but with some protection on hot days or from strong afternoon sun. The very best way to grow ranunculus is in a polytunnel, but it can also be done in a greenhouse or directly outdoors, although this requires more careful monitoring of temperature and soil dryness. The soil should be well-drained and airy, preferably mixed with compost or another nutrient-rich soil so that the moisture remains even without waterlogging. The temperature during growth should be cool to moderate, as ranunculus does not tolerate frost or excessive summer heat.
Ranunculus is a spring flower that thrives and blooms best below 20 °C. Once the temperature rises above 20 °C, the corms will go dormant as they “believe” summer has arrived, and flowering will stop. It usually takes about 90 days from the moment the ranunculus tubers are “awakened” from dormancy until they bloom, provided that conditions have been optimal. As we can rarely guarantee perfect conditions, expect flowering to occur about a week earlier or later than this.
Ranunculus can tolerate a few degrees of frost (some experts say down to –8 °C, others –4 °C), but it is safest to have hoops and horticultural fleece at hand in case of a cold night that is more than just a light frost. During the first nights after planting out, it is also wise to cover them, especially if they have not been pre-cultivated for long. However, if they have been kept cool during pre-cultivation, the transition to outdoor conditions is usually not too dramatic as the temperature difference is small.
When it is time to plant out, gently lift a small plant from the tray, taking care to keep as many roots intact as possible. Make a hole of the right size in the bed and plant it at the same depth as before, just as you would with plug plants. After planting, it is important to water thoroughly so that the soil settles around the roots and the plants get off to a good start.
Care and flowering
As soon as the tubers have rooted, they need to be watered regularly, but do so carefully as ranunculus does not like to stand in waterlogged soil. Feeding can help once the buds start to appear to support strong growth and encourage beautiful flowers. When buds and blooms begin to show colour, extra care is needed, especially if they are intended for cutting.
Harvest, vase life, and how to store the tubers
Harvest in the morning when there is still dew, as this means the stems are full of sap and the flowers will last longer. When the first buds appear, harvest time is near, but wait a few more days before cutting. The buds should not be fully firm but instead feel soft, a bit like a marshmallow. Harvest continuously to encourage further blooming. If cut at the right stage, the flowers will last around 10–12 days in a vase. If harvested later, when they have opened more, they can still hold up well but usually for a few days less than if picked at the soft bud stage.
Cut the stems at an angle with a clean knife or secateurs and place them immediately into clean water. With proper care, ranunculus flowers usually last about 10 days or slightly longer in a vase. This means: change the water often, remove the lowest leaves which could otherwise rot, keep the vase clean, and place it in a cool spot, away from direct heat.
When flowering ends and the leaves begin to die back, it is time to lift the tubers before the ground freezes. Clean them lightly and let them dry for a few days in an airy place. Store the tubers in a dark, cool, and dry spot over winter so you can plant them again next season and enjoy healthy, vibrant flowers once more.
Author: Johanna Damm
Fact-checked by: Erik Hoekstra
Last update: 2025-09-16