Gardening Articles: Flowers :: Bulbs
Prolific and Terrific: Ranunculus
by Michael MacCaskey
Remarkable for their many petals, ranunculus flowers make long lasting cut flowers.
Brilliantly colored flowers are ranunculus' chief attraction, and they are indeed special. They most often come in multiple layers of delicate, crepe paper--thin petals, looking like an origami masterwork. Ranunculus (R. asiaticus) excel in southern and western gardens, and make terrific container plants everywhere. They also make long-lasting cut flowers. Bulbs are widely available in Fall at retail nurseries in mild-winter climates; in Fall and early spring from mail-order catalogs.
Ranunculus leaves, grass green and vaguely celery-like, grow in a mound 6 to 12 inches across. Flowers on 12- to 18-inch stems emerge in March from fall-planted bulbs, June and July from spring-planted bulbs; they last up to six weeks. On the most common type, the Tecolote strain, flowers are mostly fully double, 3 to 6 inches wide, and available in bicolored picotee, gold, pastel mix, pink, red, rose, salmon, sunset orange, white, and yellow. The less common Bloomingdale strain is shorter, to 10 inches, with pale orange, pink, red, yellow, and white double flowers.
Where and How Ranunculus Grow Best
Broadly speaking, ranunculus are frost-hardy cool-season perennials. They perform best where winters are relatively mild and springs are long and cool. The roots tolerate soil temperatures to 10°F, while growing plants can handle temperatures below 20°F for several hours.
Ranunculus are most popular in the mild-winter regions of the South and West, in states such as California, Nevada, Arizona, New Mexico, Texas, and Louisiana (USDA Hardiness Zones 8 through 11), where they grow best. Planted there in October or November, they flower in March.
The clawlike bulbs, more correctly tubers, come in four grades or sizes. The largest, called jumbos, are the ones you should rely upon; they are at least 7 to 8 centimeters (2-3/4 to 3-1/8 inches) in circumference, or about 7/8 inch in diameter. Number one tubers are slightly smaller, 6 to 7 centimeters (2-1/4 to 2-3/4 inches); number twos are 5 to 6 centimeters (2 to 2-1/4 inches); and number threes, which are rare at retail, are 3 to 4 centimeters (1-1/8 to 2-1/4 inches).
Bulb size predicts the number of flowers. Each jumbo bulb will produce some 35 cuttable flowers, compared to a fifth as many from a number three bulb. Number ones will make about 20 flowers, number twos a dozen or more. Stick to jumbos for containers and most smaller plantings. Smaller number twos or even threes serve well for mass plantings.
At retail nurseries this fall, you can expect to pay about 50 cents for each jumbo bulb, 25 cents for number twos. Increasingly, nurseries also offer ranunculus in fall or spring as bedding plants in 4-inch pots. While the cost per bulb in pots is greater, this is a good option if you need only a few plants for a container.
Gardeners in zone 7 and north (Richmond and Reno to Minneapolis) can also grow ranunculus, but on a different schedule. In these regions, plant in early spring a week or two before the typical last frost.
Or, plant them in pots indoors in February for transplanting later. Place pots in a south- or west-facing window or under grow lights. Temperatures around 55°F are ideal. In early spring, gradually acclimate plants to outdoors by putting them out for more time each day (bring them in at night). Plant outdoors by mid-April in zones 6 and 7 (mid-May in zones 4 and 5). Spring-planted ranunculus will bloom in June or July.