Ranunculus can be planted at different times depending on your climate and growing setup:
- In mild winter climates (USDA zone 7 and warmer), ranunculus corms can be planted in early fall (autumn) so they can overwinter outdoors with protection against cold weather. They should be well established before winter. Planting in early fall also suits soil and air temperatures being warm enough for root development.
- In colder climates (USDA zone 6b and below), ranunculus should be planted in late winter to early spring, typically from March through April. This timing aligns with blooms from May through June and avoids exposure to freezing temperatures. Use low tunnels or frost covers to protect young plants from temperature swings.
- For temperate zones with distinct frost dates, ranunculus corms can be pre-sprouted indoors about 8 to 10 weeks before the last frost date, then planted outside 4 to 6 weeks before the last frost date when nighttime temperatures are generally between 45°F and 50°F.
- Ranunculus prefer soil temperatures around 50°F for planting, and they are sensitive to soggy soil or freezing conditions.
- For container planting, ranunculus corms can be planted in pots from September to December in cool greenhouses or cold frames for an earlier start.
Overall, the best generic planting windows are:
- Autumn in warm zones (7+)
- Late winter to early spring (March-April) in colder zones
Soak the corms/claws in water for a few hours before planting, plant them 2-5 cm deep with the claws facing downward, and plant in sunny, well-drained soil. Keep soil moist but not soggy. Shoots usually appear after 4-8 weeks, and blooms follow about 90 days after planting. This timing provides a good balance to avoid frost damage and achieve flowering in spring or early summer.
