How to Grow Ranunculus

By Julie Christensen

Few garden blooms are as eye-popping as ranunculus (R. asiaticus). The flowers, which emerge from early spring to summer, depending on your climate, have a large, rounded form and multiple petals. The petals resemble crepe-paper – thin and delicate. The Tecolote strain is the one most commonly grown. This group produces multi-petaled blooms in gold, salmon, yellow, orange and pink. The foliage grows in a mound about 12 inches wide, while the flowers bloom on 12 to 18 inch stems. The Bloomingdale strain produces smaller plants that grow to 10 inches tall. The flowers appear in white, pale orange, pink and yellow.

In addition to their beauty in the garden, ranunculus make long-lasting and lovely cut flowers. The blooms typically last seven days or more. White ranunculus has become a popular flower for wedding arrangements, but the colored ones are lovely in any setting.

Planting Ranunculus

Ranunculus grows from tubers that are available at nurseries in the fall or spring. For the most prolific blooms, look for tubers labeled “Jumbo.” Smaller tubers work in a pinch, but they won’t flower as well. In U.S. Department of Agriculture plant hardiness zones 8 through 10, they can be planted in the fall to bloom in March or April. North of USDA zone 8, wait to plant ranunculus until about one week before the last frost. Spring-planted tubers will flower in June or July.

Another option for northern gardeners is to start ranunculus indoors about twelve weeks before the last frost. Plant one or two tubers in a pot and place them in a bright window with a western or southern exposure. Keep the potting soil slightly moist and slowly start acclimating them to the outdoors about three weeks before planting them outside. Some gardeners advocate soaking the tubers before planting to soften them, while others say that soaking contributes to rot. If you opt to soak the tubers, do so for an hour only.

When planting ranunculus outdoors, select a bright, sunny spot. Amend the soil with compost or peat moss before planting the tubers. Ranunculus doesn’t tolerate soggy soils so perfect drainage is important. Set the tubers in the soil with the pointed part of the claw-like structure pointing down. Cover it with 1 to 2 inches of soil. Water the soil after planting and then allow it to dry out before watering again. Ranunculus benefits from a mulch of wood chips, cocoa hulls or bark.

Maintaining Ranunculus

Ranunculus is technically a frost-hardy, cool-season perennial. Like snapdragons, tulips and poppies, they thrive in bright sun and cool temperatures. However, keeping them alive from one season to the next poses several problems.

In warm climates, the tubers are prone to rot during the moist, warm weather of summer. In cool areas, they are often killed during the winter by freezing temperatures. Ranunculus tubers can only tolerate soil temperatures down to 10 degrees.

You can try overwintering them and you just might get lucky. Most gardeners, though, either grow ranunculus as annuals, discarding them at the end of each season, or dig up the tubers for dry storage. After the plants have flowered and the leaves have withered slightly, gently dig up the tubers. Wipe the soil off them and allow them to dry in a warm location for a few days. Then store them in a cool, dark location over the winter.  Ranunculus bulbs cost between 25 and 50 cents each, making them a reasonably affordable annual plant.

For more information on growing ranunculus, visit the following links:

Ranunculus is a Beautiful Challenge from Iowa State University Extension
Azalea, Cineria, Primrose & Ranunculus from Colorado State University Extension

Julie Christensen learned about gardening on her grandfather’s farm and mother’s vegetable garden in southern Idaho. Today, she lives and gardens on the high plains of Colorado. When she’s not digging in the dirt, Julie writes about food, education, parenting and gardening.