Ranunculus, or Persian Buttercup, is a popular spring flower known for its delicate, layered petals that resemble small roses. While fall planting is traditional in mild climates, planting ranunculus in spring is possible, especially in regions with colder winters. Success depends on correctly timing the planting and properly preparing the dormant, claw-like corms.
Determining the Best Planting Time for Your Climate
Spring planting depends on balancing the plant’s need for a cool growing period with avoiding hard freezes. Ranunculus are cool-season flowers that thrive in mild conditions and dislike extreme cold or intense summer heat. In regions with cold winters (generally below USDA Zone 7), spring planting is the standard method because the corms would likely freeze and rot if planted in the fall.
The correct timing involves planting the corms after the most severe winter weather has passed, but early enough for the plants to establish before summer heat arrives. Gardeners should aim to plant in late winter or very early spring, approximately four weeks before the last expected frost date. The ideal soil temperature for planting is 50–60°F. This early start is crucial, as the plants need a long, cool spring—typically 90 days—to develop their full display before temperatures consistently rise above 70°F, which triggers dormancy.
Preparing Ranunculus Corms for Spring Planting
The dormant ranunculus corms must be rehydrated before planting. This process begins with soaking the corms in room-temperature water for three to four hours. Over-soaking is a common mistake that can lead to rot, so avoid soaking them for longer than four hours.
After soaking, the corms can be planted directly, but an optional pre-sprouting step is recommended to jumpstart growth and encourage earlier blooms. To pre-sprout, place the soaked corms in a tray filled with lightly moistened potting mix, ensuring the mix is damp but not waterlogged. The tray should be kept in a cool location, ideally between 40°F and 50°F, for 10 to 14 days.
During this chilling period, the corms will swell and develop tiny white rootlets, indicating they are ready for the garden. When planting the prepared corms, place them shallowly, about two inches deep, with the “claws” pointing downwards. Adequate spacing, approximately six to nine inches apart, is necessary to ensure good air circulation and prevent fungal issues.
Ongoing Care and Bloom Expectations
Ranunculus require a location that receives full sun (six to eight hours of direct sunlight daily) to produce the most robust flowers and stems. The soil must be consistently moist, but excellent drainage is essential; waterlogged conditions will quickly cause the corms to rot.
During the active growth phase, young plants benefit from a balanced liquid fertilizer applied every two weeks to support the lengthy bloom period. Protecting the plants from temperature extremes is important, as they thrive in cool conditions but cannot handle a hard freeze. If late frosts are a risk, covering the young foliage with a frost cloth overnight provides adequate protection.
Spring-planted ranunculus typically begin to bloom about 90 days after the corms are first soaked, usually resulting in flowers in late spring to early summer. The plants will offer a continuous flush of blooms for four to seven weeks before the summer heat forces them into dormancy. To encourage more flowers and maintain a tidy appearance, remove spent blooms through deadheading.