How to Grow Ranunculus: The Complete Guide

You’ll need a spot with full sun, at least 6 hours daily, and more is better. If you live in a warmer climate, pick a location with some shelter from the sun in the hottest part of the day.

Good drainage is essential to prevent problems with rot on the corms. Light, loose soil with some compost worked in is perfect. When planting in containers, use a high-quality potting mix and be mindful of the drainage.

When to Plant Ranunculus 

Ranunculus are planted at different times, depending on your situation. For gardeners in USDA Zones 8 to 10, the corms can be planted outside in autumn for early spring blooms. The benefit of planting in fall is they will bloom earlier than spring-planted corms and possibly for longer.

If you live in Zone 7 or colder, you’ll need to either plant them by early spring or use a protected structure like a hoop house. Some home gardeners will grow them in containers to control their light and soil moisture. Flower farmers grow ranunculus in a greenhouse. 

The trick with planting ranunculus corms is to pay attention to the weather patterns in your area and plan accordingly. Planting them too late is the most common error. Also, remember: corms must not freeze. While the plants can tolerate a touch of frost, frozen corms will rot when they thaw.

For those planting in spring, start the pre-sprout process (see below) about 4 weeks before your last frost date.

How to Plant Ranunculus

Ranunculus corms are hard and dry when stored. Unlike a typical daffodil or dahlia bulb, these things can look and feel a bit dead, but they’re not. While pre-sprouting isn’t necessary, you’ll get flowers about 3 weeks earlier than if you just plunk them in the ground.

Before planting or pre-sprouting, soak ranunculus corms in cool water for 3 to 4 hours. Don’t soak longer than 4 hours. The corms will swell as they absorb water. 

To pre-sprout ranunculus:

• Sort through and discard any corms that appear to be rotting or decaying.
• Fill a seed starting tray with about an inch of moist—but not wet—potting mix.
• Lay out the corms in the tray, spaced quite closely together. They can be almost touching. The corms should be right side up so they look as if they might crawl away.
• Cover the corms with an inch or less of moist potting mix.
• Place the tray in a cool, dark location. An unheated basement or garage might be perfect, as long as it’s dark. 50°F is about perfect.
• In about 10 days, small white roots should be visible, indicating they’re ready for planting.

To plant ranunculus corms:

• Prepare the bed by loosening the soil and working in a generous layer of compost.
• Plant individual corms about 8–10 inches apart and about 2 inches deep. Remember to plant them with the “claws” pointing down so they look like they might skitter away.
• If a spell of cold weather and frosty temperatures occurs, cover them with frost cloth.

*** Ranunculus are quite susceptible to powdery mildew. To maintain good airflow and circulation around the plants, avoid overcrowding them.