Spider flower, Cleome hassleriana is a common annual flower from South America (Paraguay, Uruguay, Argentina and southern Brazil) that also goes by other common names including spider legs and grandfather’s whiskers. The common name of spider flower comes from the appearance of the long, thread-like stamens of the individual flowers and the elongate seedpods that develop below the blooming flowers. It has been a garden favorite since the 1800’s.
This tender annual grows quickly from seed to form tall, strong stems up to 6 feet tall from a stout taproot. Plants branch readily, and given enough space, can grow as wide as they are tall. The alternate leaves are palmately compound with 5-7 leaflets tapered at the base (although the leaves on the upper parts of the stems are smaller and simple).
Plants bloom from early summer until frost in a dense, 6-8 inch wide, ever-lengthening terminal inflorescence (a raceme). Each 1–1½” wide individual flower on a 2-inch pedicel has 4 reflexed light green sepals, 4 clawed petals and 6 erect to spreading stamens that grow to 3-inches long with yellow-orange anthers. The petals may be white, pink, rose or purple. The flowers may be visited by hummingbirds, hummingbird moths, many types of bees and butterflies. Bats are thought to be the main pollinator in its native tropical habitat.
Spider flower grows best in full sun in moist, well-drained soil. Although it tolerates dry conditions, watering will promote better growth and flowering, but overwatering and overfertilizing causes leggy growth. Staking is usually not necessary, except in windy locations. Pinching them back when young will promote a shorter, bushier plant, otherwise they tend to be upright and columnar. Because the plants are somewhat spiny and sticky, you may want to wear gloves when handling the plants. Cleome has few insects or disease problems and is generally not favored by deer or rabbits.
Start this annual indoors 6-8 weeks before the average date of last frost or seed directly in the garden after all danger of frost has passed. Seed must be cold stratified (just like they would be if they overwintered outside) first, press the seed into the soil without covering it (this plant requires light to germinate), then should germinate in a little over a week. Wait until the soil has warmed to plant in the garden, spacing the plants (or thin if self-seeded) at least a foot apart (up to 3 feet if you want a bushier plant). Self-seeded plants need to be thinned, or all will be weak and spindly.