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Ranunculus Corms— Harvesting, Planting, Growing & Buying Guide

Do you know Ranunculus corms need mild winters but long, cool springs to grow? However, depending on the USDA zones, there are two ways to plant them correctly!

To plant Ranunculus corms, first harvest and soak them in water for 1-4 hours and bury them about 2-3 inches deep and about 6-9 inches apart from each other, with claws facing down in a well-draining, loamy soil (pH of 6-7.2). 

However, you can overwinter them in the soil if you live in USDA zone 7 and above.

But, if you plan to grow Ranunculus from corms in zone 7 and low, you will find this entire guide!

When To Plant Ranunculus Corms?

Ranunculus species (or commonly Buttercups) belongs to the plant family Ranunculaceae with a peculiar characteristic of bearing underground modified stems called corms.

These corms are underground modification of stem which reserves food for the plant during winter.

Depending on the growth habit and seasonal characteristics, Ranunculus species can grow as a perennial or annual.

Do You Know?

You can remove the underground stems of annual Ranunculus from the soil during winter. These corms represent the growth of the previous year.

However, you can overwinter perennial Ranunculus corms on the ground, after which they can grow back the following spring.

To sprout Ranunculus corms at the right time, you must plant them during fall in the USDA zone 7 and above. However, you must wait for late winter or early spring to plant the Ranunculus corms in the USDA zone 7 and below.

Image illustrates parts of Ranunculus plant
Corm is a modified underground stem that stores up energy for the plant during dormancy.

Since the plant cannot tolerate winter frost (below 20-25°F), you must use the greenhouse tunnels or frost blankets to protect the corms from cold injuries.

Hence, if you want to grow Ranunculus corms during winter, start them indoors 4-6 weeks before the last frost and then transplant them outside in spring when the ground heats up.

Difference Between Bulb & Corm

Corms are modified underground stems, while Bulbs are modified underground leaves.

However, you can transplant many bulb-bearing plants like Daffodils the same way as corms.

Check this video to learn more about harvesting the corms of Ranunculus.

How To Grow Ranunculus Corms?

When planted from seeds, Ranunculus germinates within 10-15 days at a soil temperature of 70°F and reaches a flowering stage within 90-120 days after germination.

However, the corms take 2 weeks to sprout and reach a flowering stage within 90-120 days after the first growth.

Furthermore, the plant blooms for 4-10 weeks straight and enters dormancy.

First, dig the corms from the soil after the leaves on the plant have completely turned yellow to harvest them.

Steps To Grow Ranunculus Plant From Corms

Follow these steps to plant and grow Ranunculus using corms.

  • Wash the corms with clean water to remove all the dirt, and then soak them in room temperature water (< 55°F) for 1-4 hours.
  • Prepare a garden bed using moist, well-draining soil (pH 6-7.2). Make it at least 10 inches deep for adequate root space.
  • Dig holes about 2-5 inches deep and about 6-9 inches apart in rows of 4 along the bed.
  • Plant the Ranunculus corms with claw-side facing down toward the soil.
  • Cover the corms with extra soil from the top, then give them a generous soak with water.

Can You Split/ Divide Ranunculus Corms?

Since Ranunculus grow in clusters, with one plant attached to another using their corms, you can easily split them by hand and plant them individually!

However, if you live in more frigid zones (< 7), you may want to start them indoors during winter, about 4-6 weeks before the last frost date.

Image illustrates the steps to plant Ranunculus corms
Ranunculus corms need a soak in room temperature water for a few hours before planting.

To do this, plant the corms in separate terracotta planters at the same depth you would for the corms in the garden bed. Keep the soil temperature at around 50-55°F.

The corms will bear new roots in about 2 weeks and begin to sprout. This process is called pre-sprouting. 

But you can also store the corms and wait for the soil to attain a favorable temperature during mid to late spring (70°F).

How To Store? 

Follow these steps to preserve the corms during the frost.

  • Cleanse the soil from the harvested corms using a fine brush.
  • Spread them on a clean newspaper rack in a cool, dry place for 10-14 days.
  • Then, keep the corms in a net bag or in damp vermiculite.
  • The corms will remain viable for 3-4 weeks. So, be careful to keep a proper time of planting.

Transplanting The Corms

You can transplant the indoor-grown corms of Ranunculus after two weeks of the first shoot to reduce shock transplant.

Transplant them similarly by maintaining proper spacing between the corms and soil moisture.

Taking Care of Corms After Transplanting

Ranunculus requires a balanced set of care requirements for growth.

  • Offer 6 hours of dappled sunlight and keep them under shade during heat spells.
  • Water every 10-14 days and reduce to weekly watering after the appearance of the first foliage during spring and summer.
  • Apply fish-emulsion fertilizer 1-2 times a month during spring and summer. 
Image illustrates sprouting Ranunculus corm
You can transplant Ranunculus corms directly into the garden soil after it sprouts healthy shoots.
  • Maintain a surrounding humidity of around 40-50%.
  • Deadhead the blooms before seed production to encourage the corm growth by retaining its energy. 
  • Keep snails, slugs, aphids, and corm diseases (powdery mildew, downy mildew, and rotten corms) away using neem oil sprays, copper-rich fungicides, and deterring moisture.

Where to Buy Ranunculus Corms?

Go through these reliable sites to buy the corms/ bulbs.

Shops/ SitesDelivery/ Shipping Period
AmazonWithin 4-5 days after placing an order
Longfield GardensWithin 7 days after placing an order
Tulip WorldWithin 3-5 days after placing an order
EtsyWithin 9-11 days after placing an order

From Editorial Team


Corms can damage quickly if stayed in moisture or waterlogged soil for too long.

Hence, always keep the soil bone dry between watering sessions and store the corms between 40-60°F.

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