Cleomes, or spider flowers, are tall, striking herbaceous plants with large clusters of spider-like flowers atop single, prickly stems. This member of the Cleomaceae family grows up to 5 feet tall (1.5 m) and reseeds itself each year to form large clusters of plants. Flowers bloom from midsummer until frost in shades of pink, rose, purple and white, then turn into long fingers of seeds that burst open when dry and brown. It is native to the southern United States and South America.
Although cleomes are annuals, these flowering plants are at home in the perennial garden, especially as a back border. They can be mistaken for perennials, because their reseeding habit means they frequently return every year. Small volunteer seedlings appear in spring and quickly grow into tall flowering plants.
These annuals will grow in just about any soil and withstand drought conditions well. They prefer full sun but will grow in partial shade, though they may not bloom as profusely as in areas where they receive a full day of sunshine. Their height makes them unsuitable as potted plants. They do, however, make long-lasting cut flowers.
Cleome hassleriana is the most widely available variety and is frequently sold as a mix of seeds with flowers in all of the cleome colors. Though the most commonly seen cleomes are the tall varieties, a few smaller species have been developed. One of these is Senorita Rosalita cleome, which grows to just 2 feet or 3 feet (0.6 m to 0.9 m) and, unlike its larger relatives, is thornless. Another advantage of the Senorita Rosalita for some gardeners is that this variety is sterile and produces no seeds.
Cleomes are fairly easy to grow, but they can be unpredictable when starting from seed. They do best when refrigerated for a few days before being planted. Their germination rate is staggered, with seedlings appearing gradually over the course of a few weeks, though the first may appear after about a week. They prefer to be directly seeded outdoors in spring, after the soil has warmed. Cleome seeds should be barely covered with soil and kept well-watered until they sprout.
The scent of the cleome plant is very strong, with various opinions regarding what it resembles. While some say it has a minty aroma, others compare it to the scent of a skunk. Still others say it smells like cat urine. The smell is strong enough to discourage many gardeners from growing cleome at all.