Nothing compares to a vase of homegrown ranunculus. With their layered petals, they appear soft, delicate, and luscious鈥攂ut also have a sturdy stem perfect for cut flowers. Plus, these fragrant, colorful beauties attract bees and pollinators. Learn how to plant, grow, and care for ranunculus bulbs.
About Ranunculus
Ranunculus is a genus of hundreds of species, but the one we grow as a cut flower is Ranunculus asiaticus and its various hybrids and cultivars. Their rose-like blooms of layered petals can be any shade from white to pinks, salmons, creams, yellows, oranges, reds, and purples. Big blooms often reach 4 to 5 inches across, and when harvested at the correct stage, vase life is fantastic.
You鈥檒l often see packaging with ranunculus 鈥渂ulbs,鈥 though they are technically 鈥渃orms,鈥 which are flat, thickened underground stems that are underground food stores. This is similar to gladiolus flowers, which also grow from corms.
The corms are planted in early spring in areas that aren鈥檛 winter-hardy (Zones 4 to 7); they will then bloom in late spring to early summer for 4 to 6 weeks. In warm climates (Zones 8 to 10), the corms are planted in the fall and bloom in early spring.
These cool-season flowers can be perennials or annuals. They are perennials in Zones 8 to 10, where they can overwinter. Everyone else tends to treat them as annuals and plant more corms annually, similar to many other bulbs.
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 .
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鈥攂ut not wet鈥攑otting 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掳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鈥10 inches apart and about 2 inches deep. Remember to plant them with the 鈥渃laws鈥 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.
Growing
Ranunculus like cool weather and may benefit from a shade cloth if temperatures in your area get hot before they bloom. They love weather cooler than 70鈩.
Use a drip-line鈥搕ype system to keep them evenly watered, and water from below, if possible. If watering by hand, apply water at the base of the plant and attempt to avoid wetting the leaves.
Types
All ranunculus are gorgeous. Here are a few of my favorites.
Amandine ranunculus are a little more heat tolerant than some other series. Try 鈥楤arby鈥 for a gorgeous pink and 鈥楶orcelain XL鈥 for giant, dreamy pastel blooms.
La Belle ranunculus are shorter and highly productive. Check out 鈥楥hampagne鈥 for soft salmon and apricot colors and 鈥楥appucino鈥 for a two-tone stunner.
Tecolote ranunculus are meant for the vase, with 5-inch blooms and an extra full look. You can鈥檛 go wrong with any of them, but 鈥楳erlot鈥 bouquets put regular roses to shame.
Harvesting
Harvesting ranunculus is similar to peonies. You’re looking for buds starting to show color, and the main bud (if there is more than one on the stem) should feel a bit soft, like a marshmallow, not hard, like a marble.
Properly harvested and treated, ranunculus blooms are famous for their long life in the vase, easily lasting 10 days.
Cut individual stems deeply to encourage more long-stemmed blooms.
Remove foliage lower than the waterline in the vase.
Place cut stems immediately in water and enjoy!
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Wit and Wisdom
Ranunculus likes cool weather and will towards 80鈩. If you鈥檝e grown ranunculus in the past but not gotten blooms, try planting them earlier in spring to give them more time in the cool weather.
Ranunculus corms can be dug and stored over winter, just like dahlias. Wait until the foliage has died back to dig them up. Shake off the soil, let them dry, and then tease apart the individual corms, being careful to avoid breaking any of the 鈥渢entacles.鈥 Store cool and dry until pre-sprouting time.
Andy Wilcox is a flower farmer and master gardener with a passion for soil health, small producers, forestry, and horticulture. Read More from Andy Wilcox