How to Grow and Care for Ranunculus Flowers

The ranunculus flowers (Ranunculus spp.) that florists and gardeners love for floral arrangements bloom in a rainbow of colors—yellow, pink, orange, red, purple, and white. Planted as tuberous corms in the fall in warmer zones, ranunculus is a perfect companion to spring-blooming daffodils, tulips, and hyacinths in a flowering border or container.

There are dozens of species of ranunculus that range from small yellow blooms commonly called buttercups to the multi-layered, poppy-like blooms used in bouquets. Ranunculus has a level of toxicity that is harmful to humans, as well as cats, dogs, and horses.

Ranunculus Care

Ranunculus are easy to grow if planted correctly. While often sold as a spring-blooming bulb, botanically the root system is a corm. In growing areas with mild winters, the corms are planted in the fall. In zones with colder winters, the corms should be planted in early spring once the last hard frost date has passed.

Depending on your growing zone, ranunculus flowers can be annuals or perennials. Once the blooming period has passed, the foliage should be allowed to die down naturally, because the plant is still photosynthesizing and storing sugars in its corms to prepare for the next season’s growth. In zones 8 through 11, the corms will usually overwinter in the ground or a container if undisturbed. However, corms must be protected from freezing temperatures. In colder zones 3 through 7, the corms should be dug up, stored, and replanted in the spring. Flowering occurs about 90 days after planting the corms.

While prized as cut flowers for bouquets, ranunculus attract pollinators in the garden and serve as food for hummingbirds. 

Planting

The timing and technique for planting corms varies, depending on growing zones. Ranunculus corms are extremely cold-sensitive and must be protected from freezing temperatures. In zones 7 through 10, plant corms in fall for late winter/early spring blooms that come earlier and usually bloom a few weeks longer than spring-planted corms. Protect the area from freezing temperatures with a low tunnel/frost cloth.

In zones 4 through 6, plant pre-sprouted corms in spring. About 4 weeks before the last frost date, soak the corms in a bucket of room-temperature water, not warmer than 55 degrees Fahrenheit. Change the water every hour (or use a fish pump to aerate the water), soaking for a total of 4 hours. Fill a flat bottomed planting tray (without drainage holes) with 1 to 2 inches of lightly moistened grow mix. Make sure the mix is not wet, as too much moisture can cause the corms to rot. Place the soaked corms with the tuberous fingers pointing down into the medium. Don't worry about spacing, as they'll only stay in the tray about two weeks. Cover the corms with an inch of lightly moistened soil.

Place tray in a cool, dark, dry space, like a basement. Keep soil slightly moist, and check daily for mold. Remove any rotting or moldy corms. Roots will form in about two weeks, and the corms will begin to sprout. The corms are ready for spring planting in the garden. Plant the corms 2 inches deep, 9 inches apart. If freeze is forecasted, cover the area with a frost cloth.

Light

For successful blooming, ranunculus should be planted in an area that receives full sun or 6 to 8 hours of sunlight daily. Less sunlight will result in fewer blooms and less sturdy stems.

Soil

Ranunculus species prized for their showy blooms must be planted in well-draining, rich, loamy soil. If planted in clay-based soils, the tuberous corms may rot if they become waterlogged.

Some native ranunculus (Ranunculus repens) fare better in wetter, heavier soils, like those along the edges of ponds. The genus name comes from the Latin word rana, meaning frog, because many species grow in damp places.

Water

Once corms are planted in the ground or a container, the soil should be kept moist but not wet. Continue watering as the foliage and flowers appear. Once the flowers are gone and the foliage has turned yellow, slow your watering schedule, especially if you plan to dig up the corms and store them for the next growing season.

Temperature and Humidity

Ranunculus flowers prefer cooler spring temperatures (the 60s - low 70s). Once the heat and humidity of summer hit, they will not produce blooms and the foliage will die back.

Fertilizer

Since ranunculus flowers have a short growing season, they do not usually require fertilization. Before planting the corms, a granular fertilizer recommended for planting bulbs can be worked into the loose, loamy soil.

Types of Ranunculus

There are numerous species of ranunculus ranging from native wildflowers to cultivars bred for showy blossoms.

• Ranunculus carolinianus: Commonly called Carolina buttercup, a native winter annual or short-lived perennial found in low woods and damp thickets.
• Ranunculus flammula: Often called lesser spearwort or sagebrush buttercup, this native ranunculus produces five-petaled small solitary yellow flowers on slender, creeping stalks and is found along lakeshores, pond margins, and other shallow water.
• Ranunculus repens: Creeping buttercup is a weedy perennial around 8-12 inches tall, but spreads to 36 inches wide. Native to Europe and Asia, this plant has naturalized in temperate regions throughout most of the U.S. and Canada.
• Ranunculus asiaticus: A tuberous-rooted plant with parsley-like leaves that blooms in late spring to early summer. Often called Persian buttercup, the cup-shaped, poppy-like flowers (to 2-inches diameter) have distinctive purple-black anthers on stems typically growing 12-24 inches tall ranging from red, pink, purple, yellow, to white.
• Ranunculus asiaticus x hybrids: The ranunculus flowers sold by florists and the tuberous corms available for home gardening are hybrids with specific qualities of stem length, size, color, and the number of petals on each bloom.
• Ranunculus asiaticus x Cloni Success ‘Venere’: Hot pink ruffled blooms with thick and sturdy stems, perfect for cutting.
• Ranunculus asiaticus x‘Elegance Giallo’: Sharp yellow color and a long-lasting cut flower.
• Ranunculus asiaticus x Amandine ‘Salmon’: Warm salmon-colored blooms ranging from light orange to pink.
• Ranunculus asiaticus x La Belle ‘White Picotee’: Cream-colored petals edged in violet and pink.
• Ranunculus asiaticus x Pon-Pon ‘Hermione’: Huge flowers with ruffled pink and white petals. When fully opened, a green center eye is revealed.
  

Pruning

Ranunculus flowers require no pruning during the growing season. Once the foliage turns yellow and dies, it can be cut down to the ground whether the corms will be left in the ground or removed.

Native ranunculus can become weedy and require removal to prevent overspreading.

Propagating Ranunculus

The most common method of propagating ranunculus flowers is to divide the corm and any offsets at the end of the growing season.

1. After the foliage has yellowed and died, cut the plant down to soil level.
2. Dig up the corms carefully and shake or wash off the soil. Remove any dried leaves or stems that remain.
3. Use sharp garden shears to divide the small off-shoots (cormels) from the main corm.
4. Allow the corms to dry in a cool, dry place and store the dry tuberous roots dry at 50 to 55 degrees F (10-13 Celsius).
5. Plant in fall in mild areas, or soak the corms in room-temperature water and pre-sprout them from spring planting.
6. Plant corms with the tuberous roots facing down at a depth of 2 inches and space plantings 9 inches apart. 

How to Grow Ranunculus From Seed

Most ranunculus flowers are grown from corms; however, it is possible to produce them from seeds. The seeds should be started indoors about 12 weeks before the average date of your last spring frost. The small plants can be transplanted outdoors when daytime temperatures are reliably in the upper 50-degree Fahrenheit range.

1. Fill a seed starting tray with growing mix and water until the mixture is moist but not standing in water.
2. Sprinkle ranunculus seed generously on top of the growing mix, sprinkle a thin layer of the seed starting mix on top of the seeds, and press the soil down gently with your hand.
3. Place the seeds under a grow light and keep the tray at a temperature of 50 degrees Fahrenheit until they germinate in about 20 to 30 days.
4. Thin the plants when the seedlings are about 2 inches high and continue growing under the grow lights.
5. Transplant the seedlings into 2- to 3-inch pots and begin to harden off the seedlings when daytime temperatures are in the upper 40s. Bring the plants indoors at night or anytime frost threatens.
6. Plant in the garden when temperatures are reliably in the upper 50 to 60-degree Fahrenheit range.

Overwintering

If you live in hardiness zones 8 through 11, ranunculus corms can be left in the ground or in a container over the winter. However, if you live in a rainy area, the corms can become waterlogged and rot over the winter.

In zones 3 through 7, remove the corms from the ground or container, remove the soil, and allow the corms to dry. Store in a cool, dry location in a mesh bag at 50 to 55 degrees Fahrenheit.

Common Pest & Plant Diseases

While aphids can become a problem, there are no other specific pests that attack ranunculus. Root rot will be an issue if the plant is overwatered or planted in clay soil.

How to Get Ranunculus to Bloom

If planted in a location with full sun, the plant will readily bloom. Plants started from seed may have fewer blooms until the corms become larger in the second season.

Common Problems With Ranunculus

• Overwatering
• Planting in clay soil
• Not enough sun
• Freezing temperatures