The Ranunculus, often called the Persian Buttercup, is highly prized for its densely petaled, rose-like flowers. These beautiful blooms grow from a specialized underground storage organ known as a corm, which appears claw-like when dormant. Although perennial in its native Mediterranean climate, Ranunculus is typically treated as an annual in most gardens due to its intolerance for harsh winters and hot, wet summers. To ensure another season of prolific flowering, gardeners must induce a period of dry dormancy by lifting and properly storing these corms.
Identifying the Right Time for Harvest
Knowing when to lift the corms directly affects their viability for the next season. The plant provides a clear signal that the energy transfer process is complete. Wait until the foliage has completely yellowed and started to turn brown naturally. This indicates the plant has finished photosynthesis and sent its stored carbohydrates back down to the corm. Prematurely digging the corms while the leaves are still green will starve them of the energy reserves required to sprout the following year.
Once the foliage is mostly withered, the corms are ready to be carefully lifted from the soil. Use a garden fork or trowel, inserting it several inches away from the plant’s base, to gently loosen the surrounding soil and avoid puncturing the corm. The corms are often located shallowly, just a few inches beneath the surface. After lifting, use shears to cut off the dead foliage and any remaining stems, leaving only the corm itself.
Cleaning and Curing the Corms
Preparing the corms for storage begins with a light cleaning. Gently brush away any excess soil clinging to the corms, taking care not to damage the delicate “claws.” Avoid washing them, as introducing moisture increases the risk of fungal or bacterial rot. If cleaning is necessary, the corms must be thoroughly dried immediately afterward.
The most important step is the curing process, which involves drying the corms until they are hard and shriveled. Spread the corms out in a single layer on a screen or wire rack to maximize air circulation. Curing should take place in a cool, dry, shaded, and well-ventilated location, such as a garage or potting shed, away from direct sunlight. The purpose of curing is to harden the outer skin, sealing it off and making it resistant to pathogens during storage.
This process typically takes between one and two weeks, depending on humidity and temperature. A properly cured corm will feel crisp and hard to the touch, appearing noticeably smaller and more shriveled than when first dug up. Only after the corms are completely dehydrated should you proceed to long-term storage, as any remaining moisture is the primary cause of mold and rot.
Establishing Ideal Storage Conditions
The success of overwintering Ranunculus depends on maintaining an optimal environment that mimics their natural dry dormancy period. The corms must be stored in a medium that is completely dry and capable of wicking away moisture.
When selecting a container, airflow is a primary consideration to prevent moisture buildup and fungal growth. Mesh bags, paper bags, or open-top crates are superior choices, as they allow for continuous air circulation around the corms and the storage medium. Never use non-porous plastic bags or sealed containers, as these trap moisture and lead to rot.
The physical location for storage should be cool, dark, and maintain a stable temperature. The ideal temperature range for Ranunculus corm storage is consistently between 40°F and 50°F (4°C and 10°C). A dry basement, unheated closet, or root cellar are good options, but any space avoiding freezing temperatures and excessive heat or humidity will suffice.
Storage Mediums
Use materials that are completely dry to maintain a low-humidity microclimate around the corms.
- Dry peat moss
- Vermiculite
- Sawdust
- Shredded newspaper
Periodically check the stored corms to ensure their health. If you notice signs of mold, the corms need more ventilation; if they appear excessively brittle or dusty, the environment might be too dry.