// SPECIES PROFILE · ANNUAL · NATIVE · POLLINATOR MAGNET

Rocky Mountain Bee Plant

Cleome serrulata

The true native cleome of the western Great Plains — a tall, fast-growing annual with airy palmate leaves and pink- purple spider-flower racemes that elongate continuously from late June until first frost. Cleome serrulata is the species (not the horticultural C. hassleriana from South America) that fed Pueblo dye traditions, supplied "Navajo spinach" to several Plains nations, and gave honey- and bumblebees one of the most reliable summer-long nectar sources on the open Plains. Reseeds gently in the NE Oklahoma garden.

// QUICK FACTS

Family: Cleomaceae (formerly Capparaceae — mustard relatives)
Group: Annual — reseeding warm-season forb
Native range: SW Canada and the western Great Plains S to N Texas, W to E California; native to W Oklahoma; adventive in NE Oklahoma
USDA hardiness: Annual; not relevant (frost-killed)
Mature size: 2–5 ft tall × 1–2 ft wide
Sun: Full sun (6+ hours)
Soil: Lean, sandy or rocky, very well-drained; tolerates poor soils; fails on rich heavy clay
Water: Drought-tolerant; xeric once established
Bloom: Late June–October; long indeterminate raceme
Flower color: Rose-pink to purple; white forms occur
Wildlife value: Native bees (esp. Bombus, Anthophora), honeybees, hummingbirds, sphinx moths; larval host for several whites and sulphurs
Reseeding: Mild self-sowing; not a thug in the moister NE OK garden
Ecological role: Native annual · pollinator nectar · long-bloom

Rocky Mountain Bee Plant (Cleome serrulata) — pink-purple spider-flower raceme — *Cleome serrulata* — the true native cleome of the western Plains, a different species from the common ornamental garden cleome. Photo via Wikipedia / Wikimedia Commons.

Identification

[ field key — leaves · flowers · pods · lookalikes ]

Habit & stem

Erect, branching herbaceous annual 2–5 ft tall with a single central stem that branches above and elongates rapidly during the warm season. Stems are smooth, glabrous, and faintly glaucous (pale-waxy). Crushed foliage has a distinct skunky-sulfur odor (the source of the alternate common name "stinking clover") that disappears on drying. Roots are taprooted and fibrous.

Leaves & flowers

Leaves are alternate, palmately compound with three lance-shaped leaflets (occasionally five), each leaflet 1.5–3" long with a smooth or finely toothed margin. The compound leaves give the whole plant a clover-like or hemp-like aspect from a distance. Flowers are borne in elongating terminal racemes: each flower has four narrow rose-pink to lavender-purple petals and six conspicuously long, exserted stamens with bright yellow anthers, giving the flower its "spider" silhouette.

Pods & seed

The fruit is the diagnostic feature: a slender pendant silique 1–2.5" long on a long thread-like stalk, splitting along two sutures at maturity to release small dark gray-brown seeds. As the raceme elongates, ripe pods at the base, open flowers in the middle, and unopened buds at the tip co-occur on the same stem — one of the most distinctive plant silhouettes on the Plains in late summer.

Lookalikes

Most often confused with the ornamental spider flower (C. hassleriana, native to South America) which has larger flowers, 5–7 leaflets, glandular-hairy stems, and is the species sold under the variety names 'Cherry Queen', 'Violet Queen', etc. Native C. serrulata is shorter, narrower, with only 3 leaflets, smooth stems, and smaller flowers. Polanisia dodecandra (clammyweed) shares similar habitats and has white flowers with very long stamens but obviously sticky-glandular foliage.

Habitat & Range in NE Oklahoma

Cleome serrulata is a true western and short-grass-prairie plant. Its native range centers on the Rocky Mountain front, the western Great Plains, and the intermountain West, extending east across Kansas, Nebraska, and the Dakotas to the western edge of the tallgrass prairie. In Oklahoma it is genuinely native west of about Interstate 35 — it is a regular roadside, ditch, and disturbed-pasture annual across the panhandle, the mixed-grass prairies of Woods, Major, and Garfield counties, and the gypsum country of Cimarron and Texas counties. East of I-35 it is largely an adventive species, persisting from cultivation, wildflower-seed mixes, and occasional roadside seedings.

In NE Oklahoma you are most likely to encounter it in three settings: in dry roadside cuts and rail-line right-of-ways where it has escaped from re-vegetation seed mixes (especially common along US 75/Highway 169 corridors); in deliberately planted pollinator beds and roadside wildflower projects of municipalities and parks departments (Tulsa, Bartlesville, Owasso); and as a reseeding annual in home pollinator gardens. It does not thrive on the heavier clay-loam soils of central Tulsa or the Verdigris bottoms, and rarely persists in fully closed-canopy sites. It is a plant of open, lean, sandy or gravelly soil where it has limited competition.

Outside cultivation it is generally well-behaved — not an aggressive invader, not on any state noxious-weed list, and ecologically additive in roadside and disturbed-ground settings where it provides high-value pollinator forage that the surrounding rangeland cannot.

Ecology & Wildlife Value

[ pollinators · nectar volume · lepidoptera · seed crop ]

Pollinators & nectar

Among the highest nectar-volume per flower of any Plains annual, and the source of the species name “bee plant.” The flowers are thoroughly worked by honeybees (Apis mellifera), bumblebees (Bombus pensylvanicus, B. impatiens), digger bees (Anthophora, Diadasia), leafcutter bees (Megachile), and an enormous diversity of small native sweat bees. Hummingbirds and several sphinx moths (notably the white-lined sphinx) work the flowers at dawn and dusk.

Honey production

A historically important honey plant on the western Plains. C. serrulata honey is light amber, with a mild flavor, and was a significant component of late-summer honey flows for beekeepers from Colorado east through western Kansas and Nebraska. The plant's value to apiculture — combined with its long, indeterminate bloom — is the single best argument for including it in pollinator-meadow seedings even in NE Oklahoma where it is at the eastern edge of its native range.

Lepidoptera hosts

Larval host for several pierid (white and sulphur) butterflies, notably the checkered white (Pontia protodice) and the great southern white (Ascia monuste), both of which use the mustard-relative chemistry of cleomes. Adults of a much wider butterfly community visit the flowers for nectar.

Seed & bird value

Seed crop is heavy and persists through fall and winter, providing forage for mourning dove, lark bunting, savannah sparrow, and other granivorous Plains songbirds. Seed germinates readily after natural cold-stratification (winter on the soil surface) and the resulting self-seeded patches typically increase modestly each year for the first 3–4 years before stabilizing.

Native vs. ornamental cleome: Most "cleome" sold in NE Oklahoma garden centers is Cleome hassleriana — the larger South American spider flower — not C. serrulata. Both attract pollinators, but only C. serrulata is regionally native and only C. serrulata hosts our native pierid larvae. If pollinator value and ecological function are the goal, source C. serrulata seed from a native-plains specialist (Prairie Moon, Western Native Seed, Ladybird Johnson Wildflower Center seed bank).

Horticulture & Care

[ direct seeding · siting · fertility · reseeding ]

When to plant intentionally

Plant Cleome serrulata deliberately for the July–October pollinator window when most spring-blooming natives are finished and many fall composites have not yet started. It excels in lean roadside-style beds, naturalistic prairie plantings, hellstrip plantings on the south side of homes, and as a vertical accent in mixed annual borders. Do not plant in rich vegetable beds (excess nitrogen produces leafy weak plants that flop) or in heavy clay soils that stay wet through winter (cold + wet kills seed before germination).

Direct seeding

Season: sow seed directly outdoors in late fall (Nov–Dec) for natural cold-stratification, or in early spring (March) onto a freshly raked seedbed. Spring sowing without stratification often yields very poor germination.
Site prep: rake bare mineral soil; do not amend with compost or fertilizer.
Sowing rate: 1–2 oz per 1,000 sq ft for meadow effect; broadcast and lightly press in but do not bury (seeds need light to germinate).
Water: overhead irrigation only at germination if no rain falls; afterwards leave alone.
Thinning: thin in May to 12–18" between plants for the best individual specimens; closer for cottage-garden density.

Transplanting

Cleome resents transplanting once past the cotyledon stage — the taproot is fragile and disturbance frequently kills the seedling. If you must start indoors, sow into deep biodegradable pots and transplant the entire pot intact into the ground after frost danger.

Mid-season management

Almost none. Cleome is a deliberately low-maintenance plant: no staking (stems are surprisingly wind-firm for their height), no deadheading (which shortens bloom by removing the indeterminate raceme tip), no fertilization, no irrigation in normal years. The single best management practice is to leave the plant standing through fall for seed dispersal and for late-season pollinators.

Reseeding & long-term presence

In a suitable lean-soil site, C. serrulata will modestly self-sow year over year, producing a slowly expanding patch that adds 10–30% new plants annually for the first 3–5 years and then stabilizes. Self-sown seedlings appear in May after the soil has fully warmed. To maintain the patch, leave at least a third of plants standing through winter; to limit it, simply pull seedlings in spring.

Pests & diseases

Aphids — occasional, particularly in dry hot weeks. Tolerable; do not spray (will kill pollinators).
Powdery mildew — minor, in damp shaded sites.
Damping-off — in spring sowings on heavy or over-watered soils.
Cabbage white caterpillars — cosmetic, and a desirable feature if you are also growing for native lepidoptera.

Cultural & Material Uses

Cleome serrulata has one of the longest documented Indigenous use histories of any annual on the southern Plains, used for food, dye, and medicinal purposes by numerous Pueblo and Plains nations.

Pueblo dye plant: The Pueblo peoples of the Rio Grande and the Hopi of northern Arizona used boiled and reduced C. serrulata foliage as a source of black and dark-green pigment for ceramic decoration. The reduced concentrate ("guaco") is still produced by some traditional Acoma and Zuni potters as the source of the black design pigment on their characteristic polychrome wares.
"Navajo spinach": Young shoots, leaves, and flowers were cooked as a potherb (similar to spinach or amaranth) by the Navajo, Hopi, Tewa, and several Plains nations. Boiling removes the strong sulfurous odor of fresh foliage. The seeds were ground into meal and used in porridges and breads.
Medicinal: Documented historical use as a poultice for eye complaints, fever, and stomach ailments by various tribes including the Cheyenne and Lakota. Cultural-history reference only; not a guide for self-medication.
Honey-plant economic value: A significant component of late-summer honey flows for commercial apiaries on the western Great Plains, where dryland sweet-clover plantings have declined.
Roadside re-vegetation: Routinely included in pollinator seed mixes used by Oklahoma DOT, NRCS, and municipal parks departments across the western half of the state, valued for fast establishment on lean soil and reliable annual reseeding.

Sources & Further Reading

USDA NRCS PLANTS Database — Cleome serrulata: plants.usda.gov/plant-profile/CLSE
USDA NRCS Plant Guide — Rocky Mountain bee plant (Cleome serrulata), by D. Tilley & L. St. John, Aberdeen PMC.
Lady Bird Johnson Wildflower Center — Native Plant Database, Cleome serrulata: wildflower.org — CLSE
Missouri Botanical Garden Plant Finder — Cleome serrulata.
Oklahoma State University Extension — Pollinator Plants for Oklahoma and OSU Native Wildflower seed mix references.
Wikipedia — Cleome serrulata: en.wikipedia.org/wiki/Cleome_serrulata (CC BY-SA 4.0; portions of the description, ethnobotany, and pollinator sections summarize Wikipedia content).
Moerman, D.E. (1998), Native American Ethnobotany, Timber Press — Pueblo, Navajo, and Plains uses of C. serrulata.
Xerces Society — Plants for Pollinators in the Southern Great Plains, Rocky Mountain bee plant entry.
Oklahoma Biological Survey — county-level records of C. serrulata across the state.
Schiebout, M.H. et al. (2019), surveys of native bee visitation to Cleome serrulata on Great Plains pollinator plantings.

Companion Planting

[ guild · polyculture · cross-layer pairings ]

In a tallgrass prairie or pollinator meadow, rocky mountain bee plant pairs naturally with: american persimmon (Diospyros virginiana), american beautyberry (Callicarpa americana), maypop / passionflower (Passiflora incarnata), big bluestem (Andropogon gerardii), cowpea / black-eyed pea (Vigna unguiculata), and black-eyed susan (Rudbeckia hirta).

Combine rocky mountain bee plant with the warm-season grasses listed above for a self-sustaining matrix.