Ranunculus (Ranunculus species) is an often-overlooked fall-planted and spring-flowering bulb that has recently become one of my favorite spring flowers to grow. It’s an attractive addition to flowering borders when interplanted with other spring-flowering bulbs like tulips, daffodils, anemones, and hyacinths, and it even performs and looks great in containers! Plant habit also comes in many forms, from compact and stout to plants with long flowering stem lengths, perfect for cutting. I particularly love using the multi-layered, almost paper-like blooms in flower arrangements, as they have an excellent vase life as well.
Ranunculus is marketed and sold as a flowering bulb, although botanically, it’s not a true bulb. Ranunculus’s storage organ is a corm, a modified swollen stem base that stores energy reserves. Ranunculus grows well in regions with mild winters and long cool springs and is usually planted in the fall. Areas with colder winters should plant their corms in late winter or early spring once extreme hard frost dates have passed.
When preparing to plant ranunculus outdoors, a usual recommendation is to pre-soak the corms in room temperature water for several hours, allowing the corms to re-hydrate, resulting in a more uniform flowering response. The corms transform in size and shape from shriveled up claw-like structures to plump and juicy octopus-looking creatures.
Select a growing site that receives at least 6 to 8 hours of sunlight and is well-drained. Plant corms “claw” end facing down at a depth of 2 to 3 inches and space plantings 3 to 6 inches apart. Plants are quick to sprout after planting if pre-soaked and will typically flower about 90 days after planting, with the flowering period lasting up to 6 to 7 weeks.
If choosing to plant ranunculus in containers, select a pot to accommodate the full-grown plant size and ensure adequate drainage to avoid root rot.
Ranunculus will slowly fade out as the cool weather of spring comes to an end and the hot months of summer begin. Once ranunculus has ceased flowering, allow the foliage to dieback, or turn yellow before cutting, as the plant is still photosynthesizing and storing sugars in its corms to prepare for the next season’s growth. In most of South Carolina, ranunculus corms will overwinter in the ground, but in colder climates (USDA Zones 3 to 7), they are treated like an annual, and dormant corms are dug up after foliage dies back and then stored away for planting again in the fall/winter.
For more information, see HGIC 1155, Spring-Flowering Bulbs.