Ornamental · Cleomaceae
Cleome
Cleome hassleriana
Sow it once in full sun and the spider flower rockets up, blooms till frost, and bounces 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 the tall garden annual that brings real drama to a summer bed, throwing up airy, whiskered blooms that crown its stems for months. Look close and every flower flings out long stamens and slim seed pods that splay like spider legs, and that is exactly how it landed the name. It rockets to 2 to 6 feet (60 to 180 cm) in a single season, so it owns the back of a border.
Best of all, it barely asks for a thing. Hand it full sun and ground that drains, and it powers through heat, dry spells, and lean soil that would flatten fussier flowers. The one trade-off is its self-sowing streak, since it drops seed that springs up as volunteers the next spring unless you snip the spent pods.
From early summer until the first frost takes it down, the flowers buzz with bees, butterflies, and hummingbirds working every bloom. The stems carry small prickles and the leaves give off a musky scent, so pull on gloves before you dig in, or grab one of the thornless, scentless selections instead.
Care
The short version: full sun, average well-drained soil, and just the odd drink once the plant gets going. Go light on the fertilizer, pinch young plants to keep them bushy, and deadhead the pods if you would rather skip a wave of volunteers next year.
Light
Cleome craves full sun, 6 or more hours a day to stand tall and flower its heart out. It will take a touch of afternoon shade, but starve it of light and you get tall, floppy stems with hardly any blooms.
Water
Keep the soil moist while plants are young, then back right off once they get going, since cleome laughs off dry spells. Water through a real drought and no further, because overwatering kicks off the soft, leggy growth nobody wants.
Soil
Average, well-drained loam is its happy place, though it powers through clay or rocky ground as long as water moves on. Aim for a pH of 6.0 to 7.0, and skip the heavy enriching, since lean ground keeps the plant tight and compact.
Temperature
Cleome lives for warmth, growing flat out between 55°F and 90°F (13°C to 32°C). It needs heat to fire up and will not ride out a frost, so it blazes through a single season in cold-winter gardens.
Humidity
Everyday outdoor humidity is no sweat, so there is no level to chase. Air circulation is the real player, since crowded, still plantings hand mildew and rust an easy opening on the leaves.
Feeding
Feed lightly through the growing season with a balanced fertilizer, once a month tops. Pile it on and it backfires into a soft, leggy plant with weak stems, so when in doubt, feed less.
Pruning
Pinch the stem tips in early summer to fire the plant into bushier, branching growth. Deadhead or strip the spent seed pods through the season to keep that eager self-seeding reined in.
Size & spacing
Plants shoot up 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 never gets a foothold.
When to plant
Cleome is a warm-season annual that craves heat and refuses frost. Start seed indoors in late winter or fire it straight into the ground once it warms, then ride 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 most carefree flowers going, and almost everything that trips it up comes down to too much water, too little sun, or crowding. Match what you see below, and the fix is usually one quick change to how you are growing it.
Stems racing up tall and floppy with tons of leaf and few flowers
Soft leggy growth almost always tracks back to too much water or feed, or a spot that runs short on sun. Dial both down, get the plant into full sun with 6 or more hours of light, and watch it firm right up. Pinch those stem tips in early summer and it throws out lower branches that fill in fast.
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 turning up on the leaves
Hot, sticky weather plus a packed bed is what wakes up powdery mildew and rust. Open the planting up to get air moving, strip off the worst leaves, and aim your water at the base so the foliage stays dry. Give each plant 10 to 15 inches of elbow room and you head most of it off before it starts.
Fix:
- Improve air circulation
- Remove affected foliage
- Water at the base to keep leaves dry
New growth twisting up with a sticky film on the leaves
Clusters of aphids, spider mites, or whiteflies pile onto the soft new growth and leave a sticky film as their calling card. Blast them off with a strong jet of water, and only break out insecticidal soap if they dig in hard. A vigorous, unstressed plant powers through most of this on its own.
Fix:
- Spray off with a strong jet of water
- Apply insecticidal soap if infestation is heavy
Holes and notches chewed clean through the leaves
Small holes usually mean flea beetles or cabbage budworm are grabbing a meal. Pick off any caterpillars you spot by hand and keep going. Cleome is tough and rarely bothered by pests, so a healthy plant in full sun blasts right past a little chewing.
Fix:
- Handpick caterpillars
- Tolerate minor damage as plants are generally pest-free
Toxicity
Pet owners, breathe easy: cleome is non-toxic to cats, dogs, and horses, and the ASPCA logs no cases of toxic ingestion. The one thing to watch is the prickly stems and musky leaves, so keep gloves handy when you handle the plant.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
Let a curious cat poke around, since the ASPCA lists spider flower as non-toxic to cats and a nibble does zero harm. The only catch is the prickly stems, and a cat dodges those all on its own.
Dogs Safe
Dogs run no poisoning risk around cleome at all. A dog that goes overboard on any plant might get a mildly upset stomach, but the foliage itself packs nothing harmful.
Horses Safe
Cleome is safe for horses and carries no known toxins. Better yet, its musky scent steers grazers off well before they ever take a bite.
Rabbits Safe
Rabbits face zero poisoning risk from cleome. The prickly leaves and strong smell send them bounding off toward tastier picks in the bed.
Livestock Safe
Cattle, goats, and sheep share a pasture or garden edge with cleome safely. No records of toxic ingestion exist, and the musky foliage rarely tempts them anyway.
Birds Safe
Cleome poses no toxic threat to backyard or wild birds, and it actually pulls them in. Pollinators and hummingbirds flock to the flowers, and the seed pods feed birds later in the season.
People Safe
Plant it around children with confidence, since no part of it is poisonous. Just slip on gloves when you handle it, because 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 shows up in a handful of named strains that differ mostly in height, color, and whether they keep the usual thorns and scent. These are the ones you will run into most.
Helen Campbell
An old favorite that fires off fragrant, pure white flowers on tall plants topping out at 4 to 5 feet.
Queen series
The classic 3 to 5 foot strain that shows up in rose, violet, pink, and white, sold as Rose Queen, Violet Queen, and the rest.
Linde Armstrong
A compact 18 to 24 inch pink pick that ditches both the thorns and the musky scent.
Senorita series
Thornless, odorless sterile hybrids grown from cuttings, so they pump out flowers all season without flinging seedlings everywhere.
How to propagate
Cleome grows from seed alone, and the fun part is it does most of the heavy lifting 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 runs on seed and nothing else, and that is half the fun. Start it indoors 6 to 8 weeks before your last frost, or sow it straight into warm ground the moment the soil hits 70°F to 75°F (21°C to 24°C). Cover the seed lightly, then watch it pop in 7 to 14 days and burst into flower about 70 to 80 days later. A few strains like the Queen series spring up better after 4 or 5 days of chilling in the fridge, and once a plant gets going it sows next year's crop for you.
Myths
Cleome is poisonous to cats and dogs.
Great news for pet owners: the ASPCA lists spider flower as non-toxic to cats, dogs, and horses, with no records of toxic ingestion. What gets mistaken for danger is the prickly stems and the musky scent, and those are only handling nuisances. Cleome is safe to grow around pets and children.
Cleome has to be started indoors and transplanted to do well.
Not so, since cleome hates having its roots disturbed and a transplant tends to sulk. Sow the seed straight into warm ground after frost and it springs up just fine on its own. Direct sowing often works as well as transplants, and once it settles in it reseeds itself freely.