Cleomes (Cleome hassleriana) are large annual plants with spider-like flowers and lacy foliage. The long stamens and clawed petals of the flowers give the plant its common name, spider flower. The white, pink or purple flowers bloom from midsummer to fall. The plant has a strong taproot and grows 3 to 6 feet tall, and 2 to 3 feet wide. There are 150 to 200 species of cleome in the world, mostly in warm tropical areas. None is native to the United States, although Cleome hassleriana has naturalized in the southeastern states. It was formerly labeled Cleome spinosa.
Cleomes grow in loamy dry soil in sun to partial shade. They will grow in areas of low fertility and moisture, but also respond well to regular watering and fertilizing. They are excellent plants for xeriscape gardens. Cleomes are tender perennials that are grown in USDA Plant Hardiness zones 4 to 11. They will reseed in zones 8 to 11.
Sow seeds indoors or outdoors four to six weeks before the predicted date of the last frost of the spring. Lightly cover the seeds and keep evenly moist. The seeds will germinate in one to two weeks; germination may be uneven. Thin the seedling to 2 feet apart. Replant the extra seedlings in another area or discard them.
Cleomes have a long bloom period, up to three months in cooler areas and six months in warmer areas. The flowers of cleomes attract hummingbirds, butterflies, bees and beneficial insects. The plants tolerate heat, drought and soil with poor fertility. Deer usually do not eat cleomes, probably because of the thorns.
Cleomes have thorns or spines. Some of the taller varieties of cleomes require staking. Use cleomes at the back of the flowerbed or underplant with smaller, bushier plants to hide the leggy lower stems of the plants. The slender seedpods of cleomes contain hundreds of seeds, which germinate readily and can be a nuisance. Regular deadheading will reduce the number of seedlings.
Serrulato solo, the only thornless cleome, has pinkish white flowers. Helen Campbell is a stately plant with large white blooms. The Sparkler series grows 3 feet tall and wide and has flowers of white, pink or rose. The Queen Series has dense 3 to 4 feet tall plants with blooms in several different colors.