Where winters are mild (zones 8 to 10, and zone 7 with frost protection), plant ranunculus corms in fall (Clemson, NC State, Fedco Seeds). In colder zones, plant in late winter or early spring once the hardest frosts are over, ideally with corms soaked and pre-sprouted indoors from late February (Clemson, Fedco Seeds). Plant claws down, about 2 inches deep, in full sun and very well-drained soil (NC State, Clemson). Flowers come about 90 days after planting (Clemson).
Ranunculus (Ranunculus asiaticus, the Persian buttercup) is a buttercup-family plant from the eastern Mediterranean, grown for its layered, rose-like flowers (NC State). It is sold with bulbs but grows from a claw-shaped corm (Clemson). It likes mild winters, cool springs and dry summers, and it hates heat and heavy clay (NC State). Clemson says flowering typically lasts 6 to 7 weeks, and Utah State's trials found the best flowering at 60 to 68°F by day and 40 to 55°F at night.
When to plant ranunculus by zone
| Area | When to plant ranunculus |
|---|---|
| Zones 8 to 10, coastal and Southern areas | Fall planting; NC State lists zones 8a to 10b, and Clemson says ranunculus is usually fall-planted where winters are mild and springs long and cool, and overwinters in the ground in most of South Carolina |
| Zone 7 | Fall planting is possible (Fedco Seeds plants zones 7 to 10 in fall; Utah State says ranunculus is reliably hardy to zone 7), but protect plants with row cover near freezing (Fedco Seeds); NC State notes injury below 28°F in North Carolina |
| Zones 3 to 6 | Plant in late winter or early spring once the hardest frosts have passed (Clemson), ideally with corms started indoors in late February or early March (Fedco Seeds); in Utah State's zone 5 trials, field yields were best from spring planting as soon as the ground could be worked |
| UK and other cool, wet-winter climates | Plant in pots under cover from September to December and move outside after the last frost, or plant directly outside up to June for autumn flowers (RHS) |
NC State's spring timing is to plant tubers outdoors several weeks before your last frost date, or to start them indoors and plant out in spring before hot weather. Utah State found a November planting in an unheated high tunnel brought peak harvest about 6 weeks earlier, and that winter protection improved yields from fall plantings. A quick way to set your date is to count back from when heat arrives: with flowers about 90 days after planting (Clemson) and buds stopping above about 70°F (Fedco Seeds), plant at least three months before your warm weather usually starts (GardenPal arithmetic from those two figures). Our planting calendar works from your last frost date or USDA zone.
Soaking and pre-sprouting
- Soak: Clemson recommends pre-soaking corms in room-temperature water for several hours so they flower more evenly; Fedco Seeds soaks for 3 to 4 hours in cool water, and Utah State's trials used 3 to 4 hours. The RHS soaks tubers for a day. After soaking, the shriveled claws plump up (Clemson).
- Pre-sprout: Fedco Seeds sets soaked corms in a tray of slightly moist potting soil under a scant inch of soil, cool and dark at 40 to 50°F for a few weeks until white roots appear, then plants them out. Utah State's trial pre-sprouted at about 70°F for a week, then about 40°F for a week.
- Don't overwater: NC State and Clemson both warn that root rot follows wet, poorly drained soil.
How deep and far apart to plant ranunculus
| Ranunculus | |
|---|---|
| Depth | 2 in (NC State, Fedco Seeds, Utah State); 2 to 3 in (Clemson) |
| Spacing | 6 to 8 in (NC State); 8 to 9 in (Fedco Seeds); 6 in (Utah State); 3 to 6 in (Clemson); 4 in in pots (RHS) |
| Which way up | Claws pointing down (NC State, Clemson, RHS) |
| Sun | Full sun, at least 6 to 8 hours (NC State, Clemson) |
| Soil | Sandy or well-drained, rich soil; no heavy clay (NC State, Fedco Seeds) |
Spacing varies a lot between sources; closer spacing gives more stems per square foot and wider spacing more air around each plant (GardenPal note). In pots, the RHS uses loam-based compost with about 20% grit for drainage.
Frost protection and heat
- Frost: NC State says ranunculus is semi-hardy, with injury below 28°F, and Utah State gives 26°F as the minimum temperature for growth. Fedco Seeds covers plants with floating row cover when temperatures approach freezing. The RHS grows pots in a cold frame or cool greenhouse and says the plants tolerate down to 32°F (0°C).
- Heat: above about 70°F, plants stop making new buds and go dormant (Fedco Seeds); shade cloth can stretch the season.
After flowering: keep or lift the corms
Deadhead to keep flowers coming (NC State). When flowering ends, let the foliage yellow and die back before cutting it, so the corms can store energy (Clemson). In most of South Carolina the corms overwinter in the ground, but in zones 3 to 7 Clemson says to treat ranunculus as an annual or dig the dormant corms and store them for replanting. Fedco Seeds says to cure dug corms for a few days and store them cool and dry. Many growers simply buy fresh corms each year (GardenPal note).
Cutting ranunculus for the vase
Fedco Seeds says to cut ranunculus when the buds show color and feel soft like a marshmallow but haven't opened. The RHS says to cut before the flowers are fully open, and that stems should last 10 to 12 days in a vase. Clemson calls them excellent in arrangements. For other cut flowers, see when to plant anemones, when to plant snapdragons and when to plant sweet peas.
Pests, voles and pets
Utah State's biggest problem in its trials was voles. NC State lists ranunculus as poisonous (low severity), a problem for cats, dogs and horses, and a cause of contact dermatitis. Keep corms and plants away from pets and wear gloves if your skin is sensitive; call a veterinarian if a pet eats any.
Ranunculus around the vegetable garden
Clemson suggests interplanting ranunculus with tulips, daffodils, anemones and hyacinths, and says it does well in containers. Because it flowers in cool weather and fades as summer arrives, a short cut-flower row that finishes before warm-season crops go in is a practical fit (GardenPal suggestion); see succession planting. Other bulbs planted now include tulips and hyacinths.
Frequently asked questions
When should I plant ranunculus?
In mild-winter areas (zones 8 to 10, and zone 7 with protection), in fall. In colder zones, in late winter or early spring once hard frosts have passed, ideally with corms pre-sprouted indoors (Clemson, Fedco Seeds).
Can I plant ranunculus in the fall in zone 6?
Usually not outdoors. Utah State says ranunculus is reliably hardy only to zone 7, and Clemson says to plant in late winter or early spring in colder areas. Utah State found fall planting in an unheated high tunnel worked.
Which way do you plant ranunculus corms?
Claws pointing down, about 2 inches deep (NC State, Clemson, RHS).
How long do ranunculus take to bloom?
About 90 days after planting, and flowering lasts up to 6 to 7 weeks (Clemson).
Should I soak ranunculus before planting?
Yes. Clemson recommends several hours in room-temperature water, and Fedco Seeds and Utah State used 3 to 4 hours. The RHS soaks for a day.
Do ranunculus come back every year?
In most of South Carolina they overwinter in the ground (Clemson). In zones 3 to 7, treat them as annuals or dig and store the corms (Clemson).
Enter your frost dates to plan fall crops and bulb planting together.
Open itSources
- Virginia Cooperative Extension, "Companion Planting in Gardening" (SPES-620P)
- University of Maryland Extension, "Vegetable Succession and Companion Planting"
- Oregon State University Extension, "Companion Planting"
- Penn State Extension, "Herbs Make Good Plant Partners and Companions"
- University of Minnesota Extension, "Planting the vegetable garden"
- USDA Plant Hardiness Zone Map
- NOAA NCEI U.S. Climate Normals (frost/freeze data)
- NC State Extension Gardener Plant Toolbox, "Ranunculus asiaticus" (Persian buttercup)
- Clemson Cooperative Extension HGIC, "Add ranunculus to your fall planting to-do list"
- Fedco Seeds, "Growing guide: ranunculus and poppy anemone"
- Royal Horticultural Society, "How to grow ranunculus"
- Utah State University Extension, "Ranunculus: fall or spring planting?" (2021 Small Farms Conference trial presentation, PDF)
Pairings are summarized in our own words from extension-service guidance. Research support for many companion effects is limited, so treat them as good habits, not guarantees.