By Julie Christensen
When you think of annuals, you probably think of compact, neatly behaved bedding plants like petunias and impatiens that require consistent babying in the form of frequent watering and fertilizing. Cleome flowers (Cleome hassleriana) will challenge everything you know about annuals.
Cleomes, often known as spider flowers, hail from South America, but can be grown as annuals in USDA plant hardiness zones 2 through 11. The plants have fragrant, sticky leaves that are bright green and palmate-shaped. The leaves have thorns at their base. The flowers are spectacular – spider-like, fragrant blooms in pink, white, purple or bicolor. Over the course of one summer, cleomes can grow 3 to 6 feet tall with a spread of 2 feet.
As a frost-tender annual, cleomes should be planted outdoors in late spring, after the last expected frost. You can start them from seed indoors 6 to 8 weeks before the last frost or buy nursery transplants. You can also sow them directly in the ground in the fall if you prefer. Plant the seeds ½ inch deep and cover them with moist soil. They’ll tolerate most soil types, including acidic, alkaline, clay and sand, so long as it drains well.
Grow cleomes at the back of a bed, spaced 2 feet apart. They tend to have sparse foliage at the bottom, so plant other plants in front of them to hide their bare knees. These interesting plants attract hummingbirds and butterflies and are deer- and rabbit-resistant.
After planting cleomes, water them frequently so the soil stays moist 1 inch beneath the surface. Once cleomes are established, they can tolerate some drought, although they’ll bloom better with slightly moist soil. Cleomes bloom from June until the first killing frost. The blooms start at the base of the plant and move upward. Older varieties sometimes have an unpleasant skunk-like smell. New hybrids have eliminated this problem.
Although you don’t really have to fertilize them, they’ll perform better if you fertilize them every six weeks during the growing season. Dilute 1 tablespoon granular fertilizer in water and soak the plants thoroughly.
Cleomes produce showy, brown seedpods after the flowers fade. You can pick these seedpods and save them for the next year, although hybrids might not grow true. If you prefer not to save the seeds, you should pick and discard the pods. If the seedpods are left in place, cleomes will self-sow aggressively, especially in warm, mild climates. You might end up with more cleomes than you ever wanted.
Pests and Problems
Cleomes, like many annual flowers, are fairly low maintenance when it comes to disease and pests. Leaf-sucking insects, including whiteflies, thrips and aphids, may bother them, although serious damage is rare. You won’t see holes in the leaves, but rather, limp, wilting leaves. You might also notice honeydew, a sticky substance secreted by the insects, on the leaves and ground. Try washing these pests off with a steady stream of water. In severe infestations, you can treat them with an insecticidal oil or soap. Apply the pesticide on a cool, cloudy day and make sure to coat the bottoms of the leaves, as well as the tops. Make a second application 7 days later, if necessary.
Mildew and rust sometimes affect cleomes. These diseases are more common in hot, humid weather. To combat these diseases, plant cleomes so air circulates freely between them. Use drip irrigation, rather than overhead sprinklers so the leaves stay dry and remove any infected leaves. You can spray the plants with a fungicide labeled for treating mildew or rust if the problem becomes severe.
Varieties of Cleome Flowers
If you like cleomes, but don’t have room for a standard variety, try ‘Linde Armstrong,’ a dwarf hybrid that grows only 2 feet tall. This hybrid has a fuller form than some cleomes and lacks the spines and unpleasant fragrance.
‘Senorita Rosalita’ is a sterile hybrid that won’t produce seed, so there’s no need to deadhead the plant. It also lacks thorns and has a pleasant scent.
Want to learn more about growing Cleome flowers?
For more information, visit the following links:
Proven Winners talks about their variety of Cleome on YouTube.
Julie Christensen learned about gardening on her grandfather’s farm and mother’s vegetable garden in southern Idaho. Today, she lives and gardens on the high plains of Colorado. When she’s not digging in the dirt, Julie writes about food, education, parenting and gardening.