Growing Ranunculus - A How-To From Corm to Bloom
Ranunculus are the darling of any spring bouquet. Fluffy, romantic, rose-like blossoms made of tissue-thin petals that almost look too perfect to be real. They are well loved by floral designers because they come in a wide range of colours, and have the soft, romantic look of a rose but last much longer in a vase.
Ranunculus are not often seen in home gardens because the corms are not often sold in garden centres but they make a great addition to a container or garden bed and are relatively easy to grow.
Here’s how to grow ranunculus like a pro.
First things first. Ranunculus grow from corms.
A corm serves the same purpose as a tuber or a bulb in that it is a thick, solid underground mass that stores starch as food for the eventual plant. But unlike tubers, corms tend to be slightly round and flattened. And unlike bulbs, corms do not produce layers (like an onion bulb).
Other plants that produce corms are anemones, gladiolus, liatris, and crocosmia.
The leaves and buds of the ranunculus will form from the top of the corm and the roots will form from the bottom.
While corms of different plants can look more bulb-like, ranunculus corms look like baby octopuses. This makes it easy to identify and also really easy to plant because unlike some other corms that are difficult to tell which side is up, ranunculus have a clear top and bottom.
Plant your ranunculus corm with the “fingers” pointing down.
When you purchase ranunculus corms they will be small, dried, and hard. This is the hibernating form of the corm that would occur naturally in its native Mediterranean region over the hot, dry summer months.
In order to wake these corms up it is essential to mimic the Mediterranean winter rainy season by either soaking the corms in buckets of water or planting them directly into the soil and keeping the soil very moist until the first sprouts are seen. Here on the flower farm, we choose to soak the corms in buckets of water and pre-sprout them into growing medium prior to planting them out. This allows us to get an earlier start on the blooms. This is an easy enough process for a home gardener to do but you can also plant the corms directly into the garden or a container and keep the soil moist (but not soggy because the corms and new roots will rot in excessive moisture). They will take a little longer to get started when planted directly but they will still successfully grow and bloom.
If you decide to try soaking and pre-sprouting, soak the corms in a bucket of water for 2-4 hours. It is imperative that the water stay oxygenated so leave a trickle of water running from the tap into the bucket. The soaked corms can be planted directly into the garden or they can be pre-sprouted by layering them in a tray with 2.5cm (1in) of dampened soilless medium both on the bottom and top of the corms. The corms will form roots and small buds within approximately 10 days and should be planted out into their final location at this time.
Ranunculus before and after a 2 hour water soak. The “fingers” of the corm on the right are fully plumped and ready for planting.
As with all plants, if we can mimic the conditions of the native environment, our ranunculus will grow happy and healthy. Knowing that they will begin to sprout after a rainy, Mediterranean winter breaks the dry dormancy and that they will go dormant again when the soil gets hot and dry, we can predict that ranunculus prefer to grow in the cool days of spring. Thus, corms should be planted as early as possible in the spring into a sunny location.
Plant the corms 15cm (6in) to 22cm (9in) apart and 2.5cm (1in) deep. The corms can easily be planted into a container as they have a very shallow root system and do not require much depth for growing.
When finding the perfect planting location, try to avoid an area with overhead watering as ranunculus foliage is highly susceptible to powdery mildew.
Approximately 90 days after planting, your ranunculus will begin blooming and its beautiful show will last for 4-6 weeks. The bloom time will be cut short if the temperatures start to soar so be prepared to provide a little shade if you want to extend the bloom.
Once the blooms have finished and the summer is heating up, the ranunculus foliage will begin to yellow and die back, preparing for the dormancy of another hot summer.
Corms are hardy to zone 8, so in the Okanagan they will either need to be dug out after they have gone dormant in the summer and stored dry, or they need to be planted into a container that can be stored dry in a heated garage for the winter.
Now you’re all ready to try your hand at growing ranunculus in your own garden. Already tried these beauties? Drop us a line and let us know how the experience was for you.
4 thoughts on “Growing Ranunculus from corm to bloom”
Any fave suppliers of corms?
You bet! I am selling them. =)
Hello my friend! You are right – they are not always easy to find – and I have never planted them before. Embarrassing admission of a person who has been gardening for 40 years! My question is : if I get them in the ground by mid May – I won’t see blooms till mid to late August. That’s almost the end of summer! I guess they are worth waiting for.
That will be too late to get any blooms as they need cool weather to produce. They need to go into the ground as soon as the ground is thawed. I would recommend planting in mid-March here in the Okanagan. They will put on their show in about the middle of June.