Spider Flower

Cleome hassleriana is native to South America, specifically the subtropical and temperate regions of southeastern Brazil, Paraguay, Uruguay, and Argentina.

• First described scientifically in the 19th century and named in honor of the Swiss botanist Hans Hassler, who collected extensively in Paraguay
• The genus Cleome comprises approximately 170 to 200 species distributed across tropical and subtropical regions worldwide, with centers of diversity in Africa and the Americas
• Cleome hassleriana was introduced to European and North American gardens in the 1800s and has since become a staple of cottage gardens and mixed borders
• In its native range, it grows in open grasslands, disturbed areas, and along roadsides
• The family Cleomaceae was historically included within the Capparaceae (caper family) but was separated based on molecular phylogenetic evidence in the late 20th century

Cleome hassleriana is a fast-growing, erect annual herb that can reach impressive heights in a single growing season.

Stems & Foliage:
• Stems are tall, branching, and somewhat woody at the base, typically growing 90–150 cm (3–5 ft) tall, though some cultivars can exceed 180 cm (6 ft)
• Stems are covered with fine glandular hairs and may bear small spines or prickles at the leaf nodes
• Leaves are palmately compound with 5 to 7 lanceolate leaflets, each 5–12 cm long
• Leaflets are bright green with serrated margins and arranged in a palmate pattern radiating from a central point
• The entire plant has a somewhat sticky or resinous texture due to glandular trichomes

Flowers:
• Flowers are borne in large terminal racemes (elongated clusters) that can reach 15–30 cm in length
• Each individual flower has 4 petals (a trait shared with the related Brassicaceae family) arranged in a cross-like pattern
• Petals are typically 2–4 cm long, in shades of white, pink, rose, or purple
• The most distinctive feature: 6 extremely long, thread-like stamens that extend well beyond the petals (up to 5–8 cm), creating the characteristic spider-like silhouette
• Flowers open progressively from the bottom of the raceme upward, ensuring a long blooming period
• Blooms are fragrant, particularly in the evening hours

Fruit & Seeds:
• After pollination, flowers develop into elongated, slender seed capsules (siliques) 5–12 cm long
• Capsules are held on long stalks that extend outward from the stem, adding to the plant's ornamental appeal
• Each capsule contains numerous small, round, dark brown to black seeds (~1.5 mm diameter)
• Seeds are dispersed explosively when the mature capsule dehisces (splits open) — a mechanism known as ballistic seed dispersal
• A single plant can produce thousands of seeds, contributing to its prolific self-seeding habit

Cleome hassleriana thrives in warm, sunny environments and is well-adapted to disturbed and open habitats.

• Native habitat includes open grasslands, savanna margins, roadsides, and disturbed areas in subtropical South America
• In cultivation, it performs best in full sun and tolerates heat and moderate drought once established
• Highly attractive to pollinators: long-tongued bees, butterflies, and hummingbirds are frequent visitors to the nectar-rich flowers
• The evening fragrance of the blooms also attracts nocturnal pollinators such as moths
• Self-seeds aggressively in favorable conditions, sometimes naturalizing in warm climates (USDA zones 10–11)
• Generally resistant to deer and rabbits due to the sticky, aromatic foliage and prickly stems
• Susceptible to powdery mildew in humid conditions with poor air circulation

Cleome hassleriana is one of the easiest and most rewarding annuals to grow, making it an excellent choice for beginner gardeners and experienced horticulturists alike.

Light:
• Full sun is ideal (minimum 6–8 hours of direct sunlight per day)
• Can tolerate partial shade but will produce fewer blooms and may become leggy

Soil:
• Adaptable to a wide range of soil types, from sandy to clay
• Prefers well-drained, moderately fertile soil
• Tolerates poor, dry soils better than many other garden annuals
• Soil pH: slightly acidic to neutral (6.0–7.0)

Watering:
• Water regularly during establishment; once rooted, the plant is moderately drought-tolerant
• Avoid overwatering — soggy soil can lead to root rot
• Water at the base to keep foliage dry and reduce fungal disease risk

Temperature:
• Warm-season annual; plant after all danger of frost has passed
• Optimal growing temperature: 20–30°C (68–86°F)
• Does not tolerate frost; will die back with the first hard freeze

Sowing & Propagation:
• Direct sow seeds outdoors after the last frost date, or start indoors 4–6 weeks earlier
• Seeds benefit from cold stratification (refrigerate for 1–2 weeks before sowing) to improve germination rates
• Press seeds lightly into the soil surface — they require some light to germinate
• Germination occurs in 7–14 days at 21–25°C (70–77°F)
• Thin seedlings to 30–45 cm apart to allow for mature spread

Maintenance:
• Generally low-maintenance; no staking required in most situations
• Deadheading spent blooms can prolong flowering but is not necessary if self-seeding is desired
• Taller varieties may benefit from wind protection or light staking in exposed locations

Common Problems:
• Powdery mildew — improve air circulation and avoid overhead watering
• Spider mites — can occur in hot, dry conditions; treat with insecticidal soap
• Aphids — occasionally colonize new growth; easily managed with a strong water spray
• Leggy growth — usually caused by insufficient light