Ornamental · Cleomaceae
Cleome
Cleome hassleriana
Sow it once in full sun and the spider flower towers, blooms till frost, and comes back on its own.
Full sun
Every 5–10 days
55–90°F · 13–32°C
70–80 days
Overview
Cleome, the spider flower, is a tall garden annual grown for the airy, whiskered blooms that crown its stems all summer. Each flower throws out long stamens and slim seed pods that fan out like spider legs, which is where the name comes from. It climbs fast to 2 to 6 feet (60 to 180 cm) in a single season, so it earns its keep at the back of a bed.
It asks for little. Give it full sun and ground that drains, and it handles heat, dry spells, and poor soil that would stall fussier flowers. The catch is that it self-sows with real enthusiasm, dropping seed that comes up as volunteers the next spring unless you snip the spent pods.
Bees, butterflies, and hummingbirds work the flowers from early summer until the first frost cuts the plant down. The stems carry small prickles and the leaves give off a musky scent, so pull on gloves before you handle it, or grow one of the thornless, scentless selections instead.
Care
The short version: full sun, average well-drained soil, and only occasional water once the plant is established. Go easy on the fertilizer, pinch young plants to keep them bushy, and deadhead the pods if you'd rather not have volunteers next year.
Light
Cleome wants full sun, 6 or more hours a day, to stand up straight and flower well. It will take a little afternoon shade, but too little light gives you tall, floppy stems and far fewer blooms.
Water
Keep the soil moist while plants are young, then ease off once they're established, since cleome shrugs off dry spells. Water during a real drought, but no more, because overwatering pushes the soft, leggy growth you don't want.
Soil
Average, well-drained loam suits it best, though it copes with clay or rocky ground as long as water moves through. Aim for a pH of 6.0 to 7.0, and don't bother enriching poor soil too much, since lean ground keeps the plant compact.
Temperature
Cleome thrives in the warmth, growing happily between 55°F and 90°F (13°C to 32°C). It needs heat to get going and won't survive a frost, so it lives a single season in cold-winter gardens.
Humidity
Ordinary outdoor humidity is no problem, so there's no level to chase. Air circulation matters more than the moisture in the air, since crowded, still plantings invite mildew and rust on the leaves.
Feeding
Feed lightly through the growing season with a balanced fertilizer, about once a month at most. A heavy hand here backfires and produces a soft, leggy plant with weak stems, so when in doubt, feed less.
Pruning
Pinch back the stem tips in early summer to push the plant into bushier, branching growth. Deadhead or strip off the spent seed pods through the season to keep the prolific self-seeding in check.
Size & spacing
Plants reach 2 to 6 feet (60 to 180 cm) tall and spread 1 to 5 feet (30 to 150 cm) wide depending on the strain. Space them around 10 to 15 inches (25 to 38 cm) apart so air moves freely and mildew stays away.
When to plant
Cleome is a warm-season annual that waits on heat and won't take frost. Start seed indoors in late winter or sow it straight into the ground once it warms, then enjoy the bloom from early summer right up 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 one of the more trouble-free flowers you can grow, and most of what goes wrong traces back to too much water, too little sun, or crowding. Match what you see below and the fix is usually a small change in how you're growing it.
Tall, floppy stems with plenty of leaf and few flowers
Soft, leggy growth usually traces back to too much water or fertilizer, or to a spot that doesn't get enough sun. Cut back on both, move the plant into full sun with 6 or more hours of light, and pinch the stem tips in early summer to push it to branch out lower down.
Fix:
- Reduce watering and feeding
- Site in full sun (6+ hours)
- Pinch back stem tips in early summer to force branching
White powdery film or rusty spots on the leaves
Hot, humid weather and crowded plants bring on powdery mildew and rust. Open the planting up so air moves freely, pull off the worst leaves, and water at the base to keep the foliage dry. Spacing plants 10 to 15 inches apart goes a long way toward heading it off.
Fix:
- Improve air circulation
- Remove affected foliage
- Water at the base to keep leaves dry
Twisted new growth and a sticky film on the leaves
Clusters of aphids, spider mites, or whiteflies suck on the soft new growth and leave a sticky residue behind. Knock them off with a strong jet of water, and reach for insecticidal soap only if they really take hold. Healthy, unstressed plants shrug off most of this on their own.
Fix:
- Spray off with a strong jet of water
- Apply insecticidal soap if infestation is heavy
Holes and notches chewed in the leaves
Small holes usually mean flea beetles or cabbage budworm are feeding. Pick off any caterpillars you find by hand. Cleome is tough and largely pest-free, so a healthy plant in full sun simply grows past minor damage.
Fix:
- Handpick caterpillars
- Tolerate minor damage as plants are generally pest-free
Toxicity
Good news for households with pets: cleome is non-toxic to cats, dogs, and horses, and the ASPCA has no records of toxic ingestion. The only thing to mind is the prickly stems and musky leaves, so keep a pair of gloves handy when you handle the plant.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
The ASPCA lists spider flower as non-toxic to cats, so a curious nibble is no cause for alarm. The only thing to watch for is the prickly stems, which a cat will avoid on its own.
Dogs Safe
Dogs can be around cleome without any risk of poisoning. A dog that chews a lot of any plant might get a mildly upset stomach, but the foliage itself holds nothing harmful.
Horses Safe
Cleome is safe for horses and carries no known toxins. Its pungent, musky scent tends to keep grazing animals away from it in the first place.
Rabbits Safe
Rabbits face no poisoning risk from cleome. The prickly leaves and strong smell usually steer them toward tastier plants in the bed.
Livestock Safe
Cattle, goats, and sheep can share a pasture or garden edge with cleome safely. There are no records of toxic ingestion, and the musky foliage rarely tempts them.
Birds Safe
Cleome poses no toxic threat to backyard or wild birds. Pollinators and hummingbirds are drawn to the flowers, and the seed pods feed birds later in the season.
People Safe
The plant is safe to grow around children, with no poisonous parts to worry about. Just wear gloves when you handle 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 carry the usual thorns and scent. These are the ones you're most likely to find.
Helen Campbell
An old favorite that carries fragrant, pure white flowers on tall plants reaching 4 to 5 feet.
Queen series
The classic 3 to 5 foot strain you'll find in rose, violet, pink, and white, sold as Rose Queen, Violet Queen, and the rest.
Linde Armstrong
A compact 18 to 24 inch pink selection that does away with both the thorns and the musky scent.
Senorita series
Thornless, odorless sterile hybrids grown from cuttings, so they bloom all season without throwing seedlings everywhere.
How to propagate
Cleome is grown from seed alone, and it does most of the work itself once it takes to a spot.
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 grows from seed and nothing else. Start it indoors 6 to 8 weeks before your last frost, or skip the fuss and sow it straight into warm ground once the soil hits 70°F to 75°F (21°C to 24°C). Cover the seed lightly, and expect it to sprout in 7 to 14 days and flower roughly 70 to 80 days after that. Some strains like the Queen series come up better after 4 or 5 days of cold in the fridge, and once a plant is established it sows the next generation for you.
Myths
Cleome is poisonous to cats and dogs.
The ASPCA lists spider flower as non-toxic to cats, dogs, and horses, and there are no records of toxic ingestion. What people mistake for danger is the prickly stems and the musky scent, which are handling nuisances. Cleome is safe to grow around pets and children.
Cleome has to be started indoors and transplanted to do well.
It actually resents having its roots disturbed, so a transplant can sulk. Sow the seed straight into warm ground after frost and it comes up fine on its own. Direct sowing often works as well as transplants, and the plant self-seeds freely once it's settled in.