Ornamental · Cleomaceae
Cleome
Cleome hassleriana
Sown once in full sun, the spider flower rises at the back of a border, blooms until frost, and returns of its own accord.
Full sun
Every 5–10 days
55–90°F · 13–32°C
70–80 days
Overview
Cleome, the spider flower, is the tall garden annual that gives a summer border its height and its sense of movement. Reaching 2 to 6 feet (60 to 180 cm) in a single season, it belongs at the back of a bed, where it lifts the eye above lower plantings and holds a long season of bloom against a fence, a wall, or an open sky.
It rewards a relaxed approach to the garden. With full sun and ground that drains, it shrugs off heat and dry spells and keeps its poise through the kind of summer that wilts more demanding flowers, which makes it a quiet anchor for a low-fuss scheme. The one thing to plan around is its habit of self-sowing, since seed left on the plant returns as volunteers the next spring unless the spent pods come off.
From early summer until the first frost, it draws bees, butterflies, and hummingbirds into the garden and into the rhythm of the day. The stems carry small prickles and the foliage gives off a musky scent, so gloves belong with the trug when you tend it, or a thornless, scentless selection can take its place in a planting near a path or a seating area.
Care
The short version: full sun, average well-drained soil, and only the occasional watering once the planting has settled. Keep the feeding light, pinch young plants for a fuller shape, and deadhead the pods when a tidy scheme matters more than next year's volunteers.
Light
Give cleome full sun, 6 or more hours a day, and it stands tall and flowers freely, the form a border leans on. A little afternoon shade is tolerable, but too little light leaves tall, floppy stems and far fewer blooms.
Water
Keep the soil moist while the planting is young, then ease off once it settles, since cleome carries dry spells without complaint. Water through a true drought and no further, because overwatering brings the soft, leggy growth that pulls a display out of shape.
Soil
Average, well-drained loam serves it best, though clay or rocky ground works as long as water moves through. Hold the pH at 6.0 to 7.0, and resist over-enriching poor soil, since lean ground keeps the planting compact and well behaved.
Temperature
Cleome lives for warmth, holding its form between 55°F and 90°F (13°C to 32°C). It needs heat to get under way and will not stand a frost, so in cold-winter gardens it plays a single, generous season.
Humidity
Ordinary outdoor humidity asks nothing of you, so there is no level to manage. Air circulation is the part that matters, because a crowded, still planting invites mildew and rust onto the leaves.
Feeding
Feed lightly through the growing season with a balanced fertilizer, once a month at most. A heavy hand works against you, leaving a soft, leggy plant with weak stems, so lean toward less when in doubt.
Pruning
Pinch the stem tips in early summer to coax a fuller, branching shape that reads well from across the garden. Deadhead or strip the spent seed pods as the season runs to keep the eager self-seeding within bounds.
Size & spacing
Plants stand 2 to 6 feet (60 to 180 cm) tall and reach 1 to 5 feet (30 to 150 cm) across depending on the strain. Set them around 10 to 15 inches (25 to 38 cm) apart so air moves through the planting and mildew keeps away.
When to plant
Cleome is a warm-season annual that waits on heat and will not stand a frost. Seed can go in indoors in late winter or straight into the ground once it warms, setting up a display that runs from early summer to the first frost.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 6 to 8 weeks before the average last spring frost
- Plant: After all danger of frost has passed and soil reaches 70 to 75°F; or direct sow then
- Harvest: Early summer until first frost
Hardiness
USDA hardiness zones: 10–11
Temperature: down to -1°C
Troubleshooting
Cleome is among the most easygoing flowers a garden can hold, and what little goes wrong tends to come back to too much water, too little sun, or a crowded bed. Read the planting against the notes below, and the answer is usually a small change to how it is grown.
Tall, floppy stems heavy with leaf and short on flowers
A border that leans and thins into leggy growth has usually been overwatered or overfed, or set somewhere too shaded to perform. Scale both back and give the planting full sun with 6 or more hours of light, where it carries itself well. A pinch to the stem tips in early summer returns the fullness a display of this kind depends on.
Fix:
- Reduce watering and feeding
- Site in full sun (6+ hours)
- Pinch back stem tips in early summer to force branching
A powdery white film or rusty marks across the planting
Through a hot, humid stretch, a crowded border can dull under powdery mildew and rust. Letting air move through the planting, clearing the worst leaves, and watering at the base to keep foliage dry restores the look. Set at 10 to 15 inches apart, the planting breathes well enough to stay clean.
Fix:
- Improve air circulation
- Remove affected foliage
- Water at the base to keep leaves dry
Twisted new shoots and a sticky sheen on the planting
Settlements of aphids, spider mites, or whiteflies on the soft new growth leave a sticky sheen that takes the polish off a border. A firm jet of water clears most of them, with insecticidal soap held back for a heavier showing. A well-kept, unstressed planting holds its composure through the rest.
Fix:
- Spray off with a strong jet of water
- Apply insecticidal soap if infestation is heavy
Small holes and notches across the foliage
A scattering of holes is the work of flea beetles or cabbage budworm passing through. Lifting off any caterpillars by hand keeps the display tidy. As an obliging, largely pest-free plant, cleome set in full sun grows past minor damage without losing its presence in the bed.
Fix:
- Handpick caterpillars
- Tolerate minor damage as plants are generally pest-free
Toxicity
For a home that shares the garden with pets, the news is easy: cleome is non-toxic to cats, dogs, and horses, and the ASPCA records no cases of toxic ingestion. The single thing to mind is the prickly stems and musky leaves, so keep gloves within reach when you tend the planting.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
A household cat can share the garden with cleome at ease, since the ASPCA lists spider flower as non-toxic and a passing nibble does no harm. The prickly stems are the only note, and a cat keeps its distance from those on its own.
Dogs Safe
A dog moving through the border faces no poisoning risk from cleome. One that grazes heavily on any plant might feel briefly unsettled, yet the foliage itself holds nothing harmful.
Horses Safe
Cleome sits safely near horses and carries no known toxins. Its musky scent tends to turn grazers away before they ever reach for it.
Rabbits Safe
Rabbits run no poisoning risk from cleome. The prickly leaves and strong scent usually send them off toward more tempting corners of the planting.
Livestock Safe
Cattle, goats, and sheep can graze a pasture or garden edge beside cleome safely. Nothing in the record points to toxic ingestion, and the musky foliage seldom draws them in.
Birds Safe
Cleome holds no toxic threat for garden or wild birds. Its flowers invite pollinators and hummingbirds, and the later seed pods become feed for birds as the season turns.
People Safe
The plant suits a household with children, with no poisonous parts to consider. Gloves are worth keeping nearby when you work with it, since the stems and leaves carry small prickles.
Stems and leaves bear prickles/spines and the foliage has a pungent, musky scent; wear gloves when handling. Thornless cultivars exist. These are handling nuisances, not toxicity.
Varieties
Cleome comes in a handful of named strains that differ mostly in height, color, and whether they keep the usual thorns and scent, which makes it easy to match one to a scheme. These are the selections you are most likely to find.
Helen Campbell
A heritage choice for a cool, all-white scheme, carrying fragrant white flowers on tall plants of 4 to 5 feet.
Queen series
The dependable 3 to 5 foot strain for mixed color, offered in rose, violet, pink, and white as Rose Queen, Violet Queen, and the rest.
Linde Armstrong
A neat 18 to 24 inch pink selection suited to smaller spaces, free of both the thorns and the musky scent.
Senorita series
Thornless, odorless sterile hybrids grown from cuttings, which hold their season-long display without scattering seedlings into a tidy bed.
How to propagate
Cleome comes from seed alone, and a settled planting takes on most of the work itself once it finds a spot it likes.
SeedEasy
Start indoors 6 to 8 weeks before last frost, or direct sow after frost when soil is 70 to 75°F · Germinates in 7 to 14 days; blooms about 70 to 80 days after germination
Cleome arrives by seed alone, which keeps a planting refreshingly simple to plan. Start it indoors 6 to 8 weeks before your last frost, or sow straight into warm ground once the soil settles at 70°F to 75°F (21°C to 24°C). Barely cover the seed, then look for it to break ground in 7 to 14 days and come into flower roughly 70 to 80 days later. A few strains such as the Queen series rise more evenly after 4 or 5 days of chilling in the refrigerator, and an established planting reseeds the next season's display for you.
Myths
Cleome is poisonous to cats and dogs.
A garden shared with pets need not exclude it, as the ASPCA lists spider flower as non-toxic to cats, dogs, and horses, with no records of toxic ingestion. The reputation rests on the prickly stems and musky scent, both handling nuisances rather than real hazards. Cleome is safe to grow around pets and children.
Cleome has to be started indoors and transplanted to do well.
It dislikes having its roots disturbed, so a move can leave a transplant sulking in the bed. Sown straight into warm ground after frost, it rises on its own without the trouble. Direct sowing often works as well as transplants, and a settled planting renews itself by self-seeding.