Ranunculus (Ranunculus spp.) adds bright color to the flower garden or bulb border from late winter to early summer. Tender, tuberous perennials, ranunculus grows in U.S. Department of Agriculture plant hardiness zones 7 through 9, where they reach a height of 10-to-24 inches tall. Used for bedding and cut flowers, ranunculus is a member of the buttercup family. Pompom-like flowers range in color from white to shades of pink, yellow and red. Plant tubers in fall within the hardiness range.
- Select a site for your ranunculus where the plants can receive five or six hours of sunlight each day in a well-drained location. Use a raised bed if good drainage cannot be assured to prevent rotting of ranunculus tubers.
- Test your soil pH levels using a home pH tester or kit, following product instructions. Adjust soil pH to a range between 6 and 7, following soil test recommendations.
- Sprinkle bone meal over the planting area, following package recommendations.
- Spread a fertilizer blend designed specifically for bulbs, using half the strength recommended by the manufacturer.
- Apply a 1- to 2-inch deep layer of organic matter, such as compost, over the planting bed.
- Cultivate the soil to a depth of 9-to-12 inches, working fertilizer and organic matter into the planting bed.
- Water the bulb bed the day before planting the ranunculus tubers.
- Set ranunculus tubers 2 inches deep and 6-to-8 inches apart with prongs down.
- Spread the ranunculus bed with 2-to-3 inches of mulch.
- Water ranunculus after leaves emerge when necessary to maintain a moist planting area but do not saturate soil. Ranunculs tubers rot very easily in wet soil. Use a soaker hose or other form of ground irrigation to avoid wetting flowers once ranunculus begins to bud.
- Remove spent flowers to encourage additional bloom.
- Stop watering and allow foliage to yellow and die down naturally after the bloom period.
- Leave ranunculus tubers in the ground when planted within the hardiness range where soil is not subject to excessive moisture.
- Apply fertilizer to the planting bed after foliage dies down. A balanced fertilizer blend, such as 10-10-10, bone meal or a fertilizer blend designed specifically for flower bulbs, can be used, following product instructions.
- Water immediately after fertilizing.
- Dig bulbs after foliage turns yellow, if desired, and cut off the tops. Digging and storing is a method of preserving ranunculus tubers often practiced in the West, according to the “New Sunset Western Garden Book.”
- Allow ranunculus tubers to dry for about one or two weeks.
- Place dry tubers in vermiculite or in loose-knit bags and hang them in an area where there is good ventilation. Store in a cool, dry place. Temperatures between 60 and 68 degrees Fahrenheit are ideal for storage of tubers.