Ornamental · Nyctaginaceae
Four O'clock
Mirabilis jalapa
Plant it once and four o'clock opens its fragrant evening flowers all summer, then sows itself for next year.
Full sun
Every 3–7 days
50–86°F · 10–30°C
60–80 days
Overview
Four o'clock earns its name by waking up at the end of the day. The trumpet-shaped flowers stay shut through the heat and unfurl in the late afternoon, filling the evening with a sweet scent that pulls in moths and hummingbirds. A single bushy plant can carry blooms in several colors at once, sometimes even striped or splashed on the same flower.
It grows fast and easy, reaching 1.5 to 4 feet (46 to 122 cm) in a season. Gardeners treat it as a tender perennial that's run as an annual in most places, since it dies back with hard frost but stores energy in fleshy, tuberous roots. Lift those roots before winter and you can replant the same plant year after year.
The trade-off is its eagerness to spread. Four o'clock drops a heavy load of seed and reseeds itself freely, which is welcome in a wild border and a chore in a tidy bed. The seeds and roots are also toxic, so it's worth knowing where it self-sows before you plant it near pets or children.
Care
The short version: give four o'clock full sun, steady moisture in well-drained soil, and a light monthly feed. Pinch it young to keep it bushy, and deadhead before the seeds drop if you'd rather not have volunteers.
Light
Four o'clock flowers best in full sun, where it stays compact and blooms heavily. It will take partial shade and still perform, but a shadier spot tends to make the stems stretch and flop.
Water
Keep the soil evenly moist through the growing season, especially in summer heat. It likes humus-rich ground that drains well and will shrug off the odd wet spell, but it doesn't want to sit in soggy soil for long.
Soil
Plant in well-drained, humus-rich loam, though four o'clock tolerates just about any soil it's given. A pH anywhere from 6.0 to 7.5 suits it, so most garden beds work without fuss.
Temperature
It thrives in warm conditions, roughly 50°F to 86°F (10°C to 30°C), and grows fast once the heat arrives. Frost kills the top growth outright, which is why it's grown as an annual in cooler regions.
Humidity
Average outdoor humidity is all it asks, so there's no number to manage. Good spacing and airflow matter more, since crowded plants flop and trap dampness around the stems.
Feeding
A balanced general-purpose fertilizer about once a month through the growing season keeps it blooming. Go easy, since too much feed, especially nitrogen, grows weak, leggy stems that lean and snap.
Pruning
Four o'clock needs little pruning, but a pinch when young builds a fuller, sturdier plant, and cutting back leggy stems tidies it up. Removing spent plants before the seeds drop is the best way to keep its self-sowing in check.
Size & spacing
Plants reach 1.5 to 4 feet (46 to 122 cm) tall and spread 12 to 24 inches (30 to 61 cm) wide. Give each one that full spacing so the branching stems have room and air can move freely.
When to plant
Four o'clock is all about warmth and has no tolerance for frost. Start the seeds indoors in late winter or sow them straight into warm ground after the last frost, and the plants flower from midsummer right through to the first hard cold of fall.
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 last spring frost; soak seeds overnight to speed germination
- Plant: After all danger of frost has passed, about the same time as tomatoes
- Harvest: Summer through fall; flowers open in late afternoon or early evening and wilt by the following morning
Hardiness
USDA hardiness zones: 9–11
Temperature: down to -7°C
Troubleshooting
Four o'clock is a forgiving plant, and most of its quirks come from its own vigor rather than pests or disease. The few things that trip up growers are soft, floppy stems, a flood of self-sown seedlings, and seeds that are slow to sprout. Match what you see below and the fix is usually simple.
Seeds that sit and refuse to sprout
The hard seed coat is the usual hold-up, since it slows down how fast water can get in, and cold soil only makes the wait longer. Soak the seeds overnight or nick the coat before sowing to give them a head start. Sow them about 1/4 inch deep and keep the soil near 68°F to 70°F (20°C to 21°C), and they break ground in 5 to 7 days.
Fix:
- Soak seeds in water overnight or nick the seed coat before sowing
- Sow 1/4 inch deep and keep soil at about 68 to 70°F
Weak, brittle stems that flop over and snap
Four o'clocks build a lot of soft, branching growth in a hurry, and the stems can't always hold it up. Too much nitrogen or a crowded spot makes the problem worse, so the plant leans and the stems break near the base. Pinch the young plants to force a bushier, sturdier shape, give each one room, and stake the tall ones if they still sprawl.
Fix:
- Provide stakes or grow among supporting companions
- Pinch young plants to promote a bushier, sturdier habit
- Avoid over-fertilizing with high-nitrogen feeds
Volunteer seedlings popping up everywhere the next year
A single plant drops a heavy load of seed, and vigorous self-seeding turns last year's flower bed into this year's crop of volunteers. Deadhead the spent blooms before the seed sets, and pull young seedlings while they're easy to lift. In colder areas you can dig and store the tuberous roots over winter and skip the reseeding altogether.
Fix:
- Deadhead spent flowers before seeds form
- Remove volunteer seedlings while young
- Dig and store tuberous roots over winter rather than allowing reseeding
Toxicity
Four o'clock is more than a pretty face, and not in a good way. The seeds and roots are toxic to cats, dogs, horses, rabbits, livestock, and birds, and they're not safe for people either, causing stomach pain, nausea, vomiting, and diarrhea if eaten. The seeds are the most dangerous part, and handling the roots can irritate sensitive skin, so plant it where pets and small children can't reach the seedpods.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Toxic
A cat that chews the seeds, roots, or foliage tends to drool, go off its food, and vomit. The seeds are the part most likely to cause trouble, so keep them out of reach.
Dogs Toxic
Dogs react much the same way, with drooling, an upset stomach, and diarrhea after they eat any part of the plant. Curious chewers that dig up and gnaw the roots are most at risk.
Horses Toxic
The alkaloids in the seeds and roots can leave a horse drooling and colicky, with diarrhea following close behind. Keep the plant well clear of paddocks and turnout.
Rabbits Toxic
Rabbits should never nibble four o'clock, since the same toxins bring on a sore, upset gut. Don't toss trimmings into a hutch or run.
Livestock Toxic
Grazing animals such as goats, sheep, and cattle can suffer stomach pain and diarrhea if they get into the foliage or dig up the roots. Fence the plant off from pasture.
Birds Toxic
The seeds are the most dangerous part for birds, and a pecked seed or chewed leaf can cause vomiting and lasting gut upset. Treat the whole plant as off-limits.
People Caution
The seeds and roots are toxic if eaten and cause stomach pain, nausea, vomiting, and diarrhea, so keep them away from small children who might mistake a seed for a treat. Handling the roots can also leave sensitive skin red and irritated, so wear gloves when you dig them.
Keep seeds and roots away from pets and children; wear gloves if you are sensitive when digging or handling tuberous roots.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Most four o'clocks are simply sold by color, but a few named selections are worth seeking out for their flowers or foliage.
'Broken Colors'
Every flower comes striped and splashed with contrasting colors, so a single plant carries blooms that no two look quite alike.
'Limelight'
Bright chartreuse leaves set off neon pink flowers for a combination that reads from across the garden.
'Marbles' series
A mixed strain of bicolor blooms streaked and splotched in shifting color pairings across the planting.
How to propagate
Four o'clock is one of the simplest plants to multiply. You can raise it from seed for a fast first-year display, or save a favorite plant by lifting its roots before winter.
SeedEasy
Sow indoors 6 to 8 weeks before last frost or direct sow outdoors after frost danger passes · Germinates in about 5 to 7 days at 68 to 70°F; blooms the first season
Seed is the easy way in, and the plants flower their first summer. Soak the seeds overnight or nick the hard coat, sow them about 1/4 inch deep, and space the seedlings 12 to 24 inches apart. Start them indoors 6 to 8 weeks before your last frost, or sow straight into warm ground once frost has passed, and they sprout in about 5 to 7 days at 68°F to 70°F (20°C to 21°C).
DivisionModerate
Lift and divide tuberous roots in fall for winter storage, replanting in spring after frost · Stored tubers resprout in spring once replanted in warm soil
Where winters turn cold, you can carry a favorite plant over by its roots, much like a dahlia. Dig the tuberous roots in fall before the first frost, shake off the soil, and store them somewhere cool, dry, and frost-free. Replant them in spring once the soil warms, and they resprout for another season.
Myths
Four o'clock is edible or harmless because it is such a common garden flower.
Being common doesn't make it safe. The seeds and roots are toxic if eaten and bring on stomach pain, nausea, vomiting, and diarrhea, and the roots can leave sensitive skin irritated. Keep the seeds away from children and pets, and wear gloves when you handle the roots.
The flowers always open right at four o'clock.
The clock has nothing to do with it. The blooms open in the late afternoon or early evening, cued by fading light rather than a fixed hour, and they wilt away by the next morning. Cool, overcast days can coax them open earlier.