Depending on where you live and what kind of setup you’re working with, you can plant your ranunculus corms in either autumn or late winter/early spring, in a place where they’ll get full sun. In areas with mild winter temperatures (USDA zone 7 and above), corms can be planted in the autumn and successfully overwintered outdoors with the protection of a low tunnel or frost cloth. In colder areas (USDA zone 6b and below), ranunculus must be grown in a minimally heated hoop house or held back and planted out at the end of winter or in early spring. If corms are exposed to temperatures below 25°F (−4°C), they will freeze and ultimately rot once they thaw, so be sure to protect them from extreme cold.
When you unpack your corms, you’ll notice they resemble little brown octopuses and are probably not what you were expecting. Don’t worry—these strange little critters will produce an abundance of striking blooms come spring. Make sure to store them in a cold, dark and dry location until you're ready to pre-sprout such as a dry basement or closet.
Pre-sprouting:
Before planting, soak corms for 3 to 4 hours in room-temperature water. It’s important that you don’t oversoak them—they will rot. As the corms soak, they will plump up, often doubling in size. After soaking, corms can either be planted directly into the ground or presprouted. Presprouting the corms before planting will mean flowers bloom a few weeks earlier.
Fill a flat-bottom seed tray half full of moist potting soil. Sprinkle the soaked corms onto the soil, and then completely cover them with more soil. Leave the tray in a cool place (40°F–50°F / 4°C–10°C) for 10 to 14 days in an area where rodents can’t find it. Check on the corms every few days, making sure the soil is moist but not soggy, and remove any corms that show signs of mold or rot. You'll begin to see the roots forming at the bottom of the corm legs and the top should show some sprouting which means they're ready to plant!
Planting Pre-sprouted Corms:
Ranunculus corms are planted 9 in (23 cm) apart at a depth of 2 to 3 in (5 to 8 cm), with 4 rows per bed. Plant corms with the “octopus tentacles” pointing down.
* Botanical Name: Ranunculus asiaticus
* Common Names: Ranunculus, Persian Buttercup
* Plant Type: Tender perennial typically grown as an annual in most climates.
* Mature Size: 1-2 feet tall, 6-12 inches wide.
* Bloom Time: Spring to early summer, depending on planting time and climate.
* Timing:
* Fall Planting (Zones 7-10): In milder climates with mild winters, plant corms in the fall (typically September to November). This allows them to establish roots over winter for early spring blooms.
* Spring Planting (Zones 3-6 and colder parts of Zone 7): In colder climates, plant corms in early spring (typically March to May) as soon as the soil is workable and the danger of hard frost has passed. You can also get a head start by starting them indoors 4-6 weeks before the last frost.
* Choose a Sunny Location: Ranunculus thrive in full sun (at least 6 hours of direct sunlight daily). They can tolerate very light afternoon shade in hot climates.
* Prepare the Soil: They prefer well-draining, fertile soil with a slightly acidic to neutral pH (around 6.0-7.0). Amend heavy clay soils with compost, sand, or other organic matter to improve drainage. Incorporate compost into sandy soils to improve water retention and fertility.
* Planting Depth and Orientation: Dig holes about 1-2 inches deep. Place the corms in the holes with the "claws" or pointed ends facing downwards. It might look a little unusual, but this is the correct orientation for the roots to grow downwards and the shoots upwards.
* Spacing: Space the corms about 4-6 inches apart.
* Cover and Water: Gently cover the corms with soil and water thoroughly. Avoid overwatering initially, as the corms are susceptible to rot before they develop roots. Keep the soil consistently moist but not waterlogged.
Care and Maintenance:
* Watering: Once growth appears, water regularly, especially during dry periods. Keep the soil consistently moist but never soggy. Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases.
* Fertilizing: After the plants emerge, you can feed them with a balanced liquid fertilizer every 2-4 weeks during the growing and blooming season. Avoid high-nitrogen fertilizers, which can promote foliage growth at the expense of flowers.
* Staking (Optional): Taller varieties or those grown in windy areas may benefit from staking to prevent the stems from breaking.
* Deadheading: Regularly remove spent flowers to encourage more blooms and prolong the flowering period.
* Pest and Disease Control: Ranunculus can occasionally be susceptible to aphids, spider mites, and fungal diseases like powdery mildew or crown rot (especially in poorly drained soil). Monitor your plants regularly and take appropriate action if pests or diseases appear. Ensure good air circulation.
* Overwintering (Optional): In colder climates (zones 3-7), Ranunculus are typically treated as annuals. However, you can try to overwinter the corms. After the foliage dies back in the fall, carefully dig up the corms, allow them to dry, and store them in a cool, dry place (like a mesh bag in a basement) until the following spring. Replant them after the last frost. Success with overwintering can be variable. In warmer climates (zones 8-10), they may naturalize and return year after year.
Enjoying Your Blooms:
* Ranunculus make excellent cut flowers. Cut the stems when the buds are showing color but are not fully open for the longest vase life.
By following these steps, you'll be well on your way to enjoying the exquisite beauty of your Ranunculus flowers! Happy planting!
Tips:
Ranunculus are heavy feeders and do well planting with ample compost (vermicompost or worm castings work great) or you can use a slow release organic fertilizer as well.
Ranunculus are also deep rooted so make sure to give them ample space (don't plant in shallow pots) so they can thrive!
Cutting:
Ranunculus have an outstanding vase life, often exceeding 10 days. Cut when buds are colored and squishy like a marshmallow, but not yet fully open, for a vase life of 10 to 12 days. If the blooms are open when cut, they’ll still last a week but will be more fragile to transport. Be sure to cut spent flowers down to the base to promote new blooms.