Ranunculus Information

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Ranunculus Information
Ranunculus (Asiatic ranunculus flowers image by Chad McDermott from Fotolia.com)

Ranunculus are vibrantly coloured flowers known for their large, showy blooms. Multiple layers of thin, delicate petals make these exquisite flowers a focal point in the garden and in cut-flower arrangements, where they can last indoors for up to seven days. Outdoors, these cold-hardy perennials are grown from bulbs and planted either directly in the ground or in container arrangements.


The most common type of ranunculus is the Tecolote variety, which comes in colours ranging from pink, red and gold to salmon, sunset orange and white. Flowers grow 3 to 6 inches wide. Stems are 12 to 18 inches long. Another variety of ranunculus is the Bloomingdale strain. This type is only 10 inches with double flowers in yellow, red, pink, white and pale orange. Foliage on the ranunculus is green and mounding 6 to 12 inches across.

Ranunculus bulbs are claw-like in shape and are available in four different sizes. Generally, the bigger the tuber, the more flowers it produces. The largest bulbs are jumbos, ranging from 2 ¼ to 3 1/8 inches in circumference. A jumbo bulb can produce up to 35 flowers. In comparison, a number 3 bulb will produce only about 5. Larger bulbs are generally used for container plantings while the smaller ones are used en masse for in-ground planting. Tubers are hard, dry specimens when purchased, but they plump up and soften once they absorb water.


As cold-hardy perennials, ranunculus requires the milder winters of USDA Hardiness Zones 8 through 11. In chillier areas, ranunculus are grown as annuals. In warmer areas of the South and West, ranunculus bulbs are planted in the fall and they flower in March. In the colder areas Zone 7 and below, gardeners should wait until spring, just before the last frost, to plant their ranunculus bulbs outdoors. If planted in the spring,you can expect blooms in June or July.

Ranunculus bulbs can also be started indoors in pots in February and then transferred outdoors when the weather warms up. Plants started indoors do need to be gradually introduced to outdoor conditions before moving them outside permanently. As far as growing conditions go, ranunculus is a flower that requires full sun exposure and well-drained soil. These plants will rot in consistently wet soil.


Once you have chosen a sunny location with good drainage, it is time to plant your ranunculus. Dig a hole in the ground or in your container that is 1 to 2 inches deep. Place the claw-shaped bulb in the hole with the pointy end down. Cover with soil, water well and apply a layer of mulch. If the soil retains some moisture, it is not necessary to water again until sprouts pop up in 15 to 20 days. Though some advocate soaking tubers in water prior to planting, this is not necessary as sometimes soaking makes them mushy.

When planting directly in the ground, use smaller tubers such as number 3s. They should be spaced about 4 inches apart. If you use jumbos, they should be spaced 8 to 12 inches apart. For containers, since ranunculus produce large root systems, you want to limit the amount of tubers you use. A standard 10-inch pot can hold three number 2s or one or two jumbos


Once sprouted, ranunculus should be watered deeply during summer and fall and fed with a water-soluble 15-16-17 NPK fertiliser on a weekly basis. Follow package directions on the fertiliser to make sure you apply the proper amount.

Deadheading faded blooms regularly promotes more flowers. The proper way to do this is to pinch off blooms near their point of origin.

When growing ranunculus as an annual, you can dig up tubers in mid-fall and store them for replanting next season. Place them in a brown paper bag and keep them at a temperature of 10 to 15.6 degrees Celsius. In zones 8 through 11, bulbs can remain in the ground. Just let the foliage die back and they will bloom again next year.

Pests and Disease

Ranunculus are hardy plants but they can be susceptible to garden pests and diseases. Some common ones to watch out for include aphids, powdery mildew and birds. Aphids are tiny green insects that feed on the sap in plant stems. Signs of aphid infestation include worn and faded leaves with curled edges. Treat infested ranunculus with a commercial pesticide or a home remedy of water mixed with dish detergent.

Powdery mildew is a common fungal infection caused by poor air circulation, humidity and excessive moisture, Leaves look dusty as if they were coated in powder. The best control is removing infected foliage with clean pruners and treating it with a commercial fungicide. The best cure is prevention, however, so this means ensuring ample space between plants and taking care to water the soil and not the foliage of the plant. Watering early in the day is also key so that moisture dries off before the cooler evening air sets in.

Birds are a threat to ranunculus only when shoots are first emerging from the soil. Once the plant hits 6 inches in height, the birds will no longer be attracted to it. Keep young sprouts covered with wire or netting until they become tall enough to not interest our winged friends.

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