The Cleo plant, botanically known as Cleome hassleriana, is a captivating annual that adds an airy, unique presence to garden spaces. Often recognized by its common name, Spider Flower, it is a favorite for its distinctive blooms and relatively simple care.
Understanding the Cleo Plant
The Cleo plant exhibits a tall, upright growth habit, typically reaching heights of 3 to 6 feet with a spread of 1 to 2 feet. Its foliage consists of palmate leaves, often with 5 to 7 leaflets, which can sometimes be sticky and emit a musky fragrance, though newer cultivars are often odorless and thorn-free.
The plant’s unique appeal stems from its spidery flowers, which display delicate petals in shades of pink, purple, white, or bicolor combinations, complemented by long, thread-like stamens that extend prominently from the bloom. These striking flowers appear in dense, ever-lengthening terminal clusters from early summer until the first frost. As the flowers fade, they are replaced by thin, spidery green seed pods that resemble spider legs as they develop below the blooming flowers.
Ideal Growing Conditions
Full sun is generally recommended for optimal growth and abundant flowering, ideally receiving six to eight hours of direct sunlight daily. While they can tolerate light shade, too much shade can result in leggy, less floriferous plants.
The plant adapts well to average, well-drained soils and shows a preference for moderately fertile conditions. Consistent moisture promotes more vigorous growth and flowering. They are warm-season annuals and are not tolerant of frost, typically thriving in temperatures between 70 and 90°F (21-32°C).
Planting and Ongoing Care
Cultivating Cleo plants can begin by sowing seeds directly in the garden after the last frost, when soil temperatures are consistently between 70 to 75°F (21-24°C). Seeds should be lightly covered with about ¼ inch of soil, as they require some light for germination, which typically occurs within 7 to 14 days. For an earlier start, seeds can be sown indoors 6 to 8 weeks before the last expected frost. When transplanting seedlings outdoors, ensure they are hardened off by gradually exposing them to outdoor conditions over a week.
Proper spacing is important for healthy plant development, with seedlings thinned to 10 to 15 inches apart, or up to 18 to 24 inches for bushier plants, to ensure adequate air circulation. Young plants should receive regular watering until they are established. Once mature, Cleo plants are relatively drought-tolerant, but supplemental watering during prolonged dry periods will encourage better bloom production. Fertilization is often minimal; amending the soil with compost before planting is usually sufficient, as over-fertilizing can lead to leggy growth.
Cleo plants are largely self-cleaning, so deadheading is not strictly necessary for continuous blooming. However, removing spent flowers can prevent self-seeding and may encourage more blooms. Pinching back young plants can promote bushier growth and a more compact form, preventing them from becoming too tall and spindly. While generally sturdy due to their taproot, very tall varieties in windy locations may benefit from staking to prevent toppling.
Common Challenges and Solutions
Cleo plants are known for their general hardiness and resistance to most pests and diseases. However, they can occasionally be susceptible to common garden pests such as aphids, spider mites, or whiteflies. Minor infestations can often be managed by hand-picking pests or spraying plants with a strong stream of water. For more persistent issues, horticultural oil or insecticidal soap can be applied.
Fungal issues like powdery mildew or rust may arise, particularly in hot, humid climates. Adequate spacing between plants to improve air circulation and watering at the soil level rather than overhead can help prevent these diseases. Cleo plants are prolific self-seeders. To manage excessive self-seeding, seed pods can be removed as they form, or a layer of mulch can be applied in spring to inhibit germination.
Popular Varieties and Garden Uses
The ‘Sparkler’ series is recognized for its more compact, bushier growth habit, making it suitable for containers, with colors including blush, lavender, rose, and white. The ‘Queen’ series, an older collection, features taller plants ranging from 3 to 5 feet, available in shades like white, rose, cherry, and purple, and is known for its aggressive self-seeding. Cultivars such as ‘Senorita Rosalita’ and ‘Linde Armstrong’ are sterile hybrids, meaning they do not produce viable seeds and are often thornless and odorless, offering a tidier option for gardeners.
Their height makes them excellent choices for background plantings in borders or as vertical accents in mixed beds. They can be planted in masses to create a dramatic, shrub-like effect or used to fill empty spaces in developing landscapes. Cleo plants also make striking additions to cottage gardens, cut flower gardens, and containers, especially the shorter varieties. Beyond their visual appeal, their nectar-rich flowers attract hummingbirds, butterflies, and bees, contributing to pollinator-friendly garden spaces.