Cleome (Cleome hassleriana), commonly called spider flower, is a tall, airy annual grown for its unusual flower clusters, whose long, dangling stamens give each bloom a spidery, almost fireworks-like look. It's an easy plant to grow from direct-sown seed and a good choice for the back of a border, since mature plants typically reach 3 to 5 feet (90 to 150 cm) tall on sturdy, upright stems. In Kentucky it grows as a true annual, killed outright by the first hard frost, but it self-seeds enthusiastically enough that many gardeners find volunteer seedlings coming up on their own the following spring. The flowers open in loose, rounded clusters that keep extending upward through the season, giving months of continuous bloom with very little care. It asks for full sun and ordinary garden soil, and beyond thinning seedlings and the occasional deadheading, it mostly takes care of itself.
Sowing and planting
Cleome grows easily from direct-sown seed, and most Kentucky gardeners skip starting it indoors altogether. Wait until after the last frost date and the soil has warmed, which in zone 6b usually falls in mid-to-late May. Scatter seed over prepared soil and press it in lightly rather than burying it deep; cleome seed needs light to germinate well, so a bare surface sowing works better than covering it with soil. Keep the seedbed evenly moist until seedlings appear, and be patient: germination is a little slow and can be uneven, often taking two to three weeks and continuing to trickle in after that.
Once seedlings have a couple of true leaves, thin them to 18 inches (45 cm) apart; crowded plants grow taller and spindlier than well-spaced ones and are more prone to flopping. If you'd rather get a jump on bloom time, nursery transplants set out after the last frost work just as well as direct-sown seed. Choose a full-sun spot, since cleome grown in partial shade stretches toward the light and produces fewer flowers.
Growing on
Cleome needs little regular care once established: water during dry spells, especially in its first few weeks, and ease off once plants are growing strongly, since established plants tolerate average garden conditions without much fuss. A light, balanced feeding at planting time is usually all it needs for the season; heavy fertilizing produces taller, floppier growth without much benefit to flowering.
Tall types can lean or flop in open, windy spots, particularly after summer storms; a stake or two worked in around the base of a clump, or planting cleome where nearby perennials offer a little support, keeps the stems upright without much effort. A practical note on handling: the stems and foliage have a slightly sticky texture and a musky scent, and the residue can mildly irritate sensitive skin. It's not a serious concern, but some gardeners prefer light gloves when working closely around the plant, including when staking or deadheading it.
Harvesting
Cleome's airy, long-stemmed clusters make an interesting addition to a cut arrangement, standing out for their spidery shape rather than for fragrance — the foliage in particular has a musky scent that's stronger up close than at a distance. Cut stems in the morning when clusters are freshly open, strip any leaves that would sit below the waterline, and expect several days of vase life.
Deadheading matters more here than with most annuals, because cleome self-seeds enthusiastically. Each spent flower spike develops long, narrow seed pods that mature and eventually split open, scattering seed through the bed and into nearby paths and beds. If you don't want volunteer seedlings carpeting the area next spring, cut spent flower spikes off before the pods mature and split open; if you don't mind the volunteers, or actually want them, you can simply let the pods ripen and let the plant reseed itself.
Problems and pests
Fine webbing or stippled leaves in hot, dry weather
Spider mites can build up on cleome during stretches of hot, dry weather, leaving leaves with a pale, stippled look and fine webbing in heavy infestations. A strong spray of water on the undersides of leaves disrupts populations, and keeping plants watered during dry spells helps, since mites multiply fastest on stressed plants.
Clusters of small insects on buds and new growth
Aphids sometimes gather on flower buds and new shoots, especially in spring. Light infestations rarely cause lasting harm and are often cleaned up by ladybugs and other predators on their own; for heavier infestations, a strong water spray or insecticidal soap handles them.
Powdery white coating on the leaves
Powdery mildew can show up during humid stretches, especially on crowded plantings with poor air movement. It's mostly cosmetic on cleome and rarely threatens the plant's survival. Give plants their full 18-inch spacing and water at the soil line rather than overhead to reduce the conditions that favor it.
Volunteer seedlings coming up everywhere the next spring
Because cleome seeds so readily, a bed left to go to seed one year often produces a thick carpet of volunteer seedlings the next. These pull easily while small, so hoe or hand-pull unwanted ones early, and deadhead the previous year's plants before pods split if you want to keep the spread in check going forward.
Leggy, bare-stemmed growth at the base
Plants grown in too much shade, crowded too closely, or left unstaked in windy spots often end up tall and sparse near the base, with bloom concentrated only at the top. Give cleome full sun and its full spacing, and stake clumps in exposed spots to keep the whole plant looking fuller rather than top-heavy.
Varieties worth growing
- Sparkler Series – A shorter, more compact series than old-fashioned cleome, with less sprawl and good branching, available in white, blush, and lavender shades.
- Senorita Rosalita – A sterile hybrid that produces no viable seed, giving continuous bloom without the self-seeding of traditional cleome, with thornless stems that are easier to handle.
- Helen Campbell – A classic white-flowered heirloom type, tall and vigorous, that breeds true from seed if allowed to self-sow.
- Queen Series – An older strain available in separate colors, including Rose Queen, Cherry Queen, and Violet Queen, with the tall, traditional cleome habit.
- Linde Armstrong – A compact, more manageable selection that stays shorter than the species, useful for smaller borders or containers.