Few flowers keep a schedule the way four o’clock flowers do. Their trumpet-shaped blooms stay shut through the heat of the day, then unfurl in the late afternoon, releasing a sweet fragrance that pulls in hummingbirds, butterflies, and night-flying moths until the next morning. Botanically known as Mirabilis jalapa, and nicknamed the Marvel of Peru, this old-fashioned cottage-garden plant is one of the easiest summer bloomers you can grow from seed, and one of the most generous once it settles in.
Part of the appeal is theater. A single plant can carry pink, yellow, white, magenta, and even striped or speckled flowers at the same time, and the show resets every evening. The rest of the appeal is how little it asks of you: four o’clocks shrug off poor soil, summer heat, and neglect, and they come back year after year either from overwintered roots or from seed they scatter themselves. Here is everything you need to plant, grow, and keep four o’clock flowers performing.
What four o’clock flowers are and why they open at 4 PM
Four o’clock flowers are bushy, fast-growing tender perennials in the Nyctaginaceae family, native to tropical Central and South America. Most gardeners grow Mirabilis jalapa, which forms a multi-branched, shrub-like mound 2 to 3 feet tall and roughly as wide in a single season. The stems are a little brittle and can flop in wind or rain, so the plants look best grown close together where they support one another.
The flowers themselves are a small botanical trick. What looks like a five-lobed trumpet is actually the pigmented calyx, the fused sepals, because Mirabilis flowers have no true petals at all. Each bloom is about two inches long and flares to an inch across, and the color range runs from white and clear yellow through pink, red, and magenta, often with bicolor stripes, splashes, or marbling on the same plant.
The name comes from the plant’s daily rhythm. Blooms open in the late afternoon, often around 4 PM, and close by the following morning. That timing is driven by light and temperature rather than a literal clock, so flowers open earlier on cloudy or rainy afternoons and may stay open all day when skies are overcast. The late opening is no accident: four o’clocks evolved to be pollinated by long-tongued sphinx moths that fly at dusk, which is also why the evening fragrance is strongest right as the flowers open.
When and how to plant four o’clock seeds
Four o’clocks are simple to start from seed, and starting from seed is by far the cheapest way to fill a bed. The large, black, grenade-shaped seeds have a hard coat, though, so two quick steps make a real difference to germination.
- Scarify the seed. Nick each seed with a knife or rub it briefly with sandpaper to break the hard outer coating. This gives water a way in.
- Soak overnight. Drop the scarified seeds in a bowl of lukewarm water for 8 to 12 hours to hydrate the embryo and signal it is time to grow.
Once that prep is done, timing depends on your climate:
- Direct sowing outdoors. After all danger of frost has passed and the soil has warmed to at least 65°F, sow seeds a quarter inch deep, spaced about 6 inches apart. Keep the bed evenly moist. Seeds usually sprout in 5 to 14 days at soil temperatures of 65 to 75°F.
- Starting indoors. In short-season regions, sow indoors 6 to 8 weeks before your last frost. Press seeds onto the surface of moist seed compost and cover only thinly with vermiculite, since four o’clock seeds need light to germinate. Hold them at 65 to 75°F, and transplant out after the frost once seedlings are hardened off.
As the plants grow, thin or space them 12 to 24 inches apart. They are fast: flowers typically appear 8 to 10 weeks after sowing, giving you bloom from midsummer right up to the first frost.
Where to plant four o’clocks for the best bloom
Four o’clocks are sun lovers. Give them a spot with at least 6 hours of direct sun for the heaviest flowering; they will tolerate part shade but bloom noticeably less in it. In very hot southern gardens, a little relief from harsh afternoon sun is fine and will not cost you many flowers.
Soil is where these plants are wonderfully forgiving. They grow in almost any soil, including poor ground, but they do best in a humus-rich, well-drained site with neutral to slightly acidic pH. The one thing they will not forgive is waterlogged ground, because the fleshy, tuberous roots rot in soggy conditions. If your soil drains slowly, work in compost, leaf mold, or well-rotted manure before planting to open it up.
Place four o’clocks where you will actually be in the evening, since that is when the show happens. Along a patio edge, beside a doorway, under a window, or toward the back of a border, the late-day fragrance and color are easy to enjoy. Planted in a row and spaced closely, they also make a fast, informal seasonal hedge.
How to care for four o’clock flowers through the season
Once established, four o’clocks need little fuss, but a few habits keep them lush and flowering hard.
- Watering. Aim for consistently moist soil that never sits wet. When the top inch of soil is dry, water; in peak summer heat that may be every other day, easing to once or twice a week by early fall. Overwatering is the main way gardeners lose these plants to root rot, so let the surface dry between drinks.
- Feeding. In rich soil, four o’clocks may need no feeding at all. In average ground, apply a balanced organic fertilizer in spring and a bloom-boosting feed, such as a high-potash tomato fertilizer, in midsummer. Stop feeding in fall so the plant channels energy into its roots rather than soft new growth that frost will kill.
- Pinching for shape. When young plants reach about 6 inches tall, pinch back the growing tips. This encourages bushier, denser plants with more flowering stems.
- Deadheading. It is optional. Four o’clocks bloom freely without it, and the spent flowers are not self-cleaning, so they hang on looking tired until they drop. Removing them tidies the plant, can extend the season slightly, and curbs self-seeding.
Containers follow the same rules but dry out faster, so check pots daily in summer and feed monthly, taking care not to keep the mix soggy.
How to overwinter four o’clocks and grow them as perennials
Whether four o’clocks behave as annuals or perennials comes down to your hardiness zone, and this is where a lot of conflicting advice circulates. Here is the simple version:
- Zones 9 to 11: reliably perennial. Roots survive the winter in the ground and resprout each spring.
- Zone 8: borderline. Cut plants back after frost and add about 2 inches of mulch over the root zone before the first hard freeze to improve their odds.
- Zones 2 to 7: grow as annuals, or lift and store the roots.
The roots are worth saving. In mild climates a four o’clock taproot can swell to a foot or more long and, over years, weigh up to 40 pounds, storing huge reserves of energy. Treat them exactly like dahlia tubers: after the foliage dies back, cut the stems just above ground, dig the roots, shake off the soil, and store them somewhere cool, dry, and frost-free. In late winter, pot them up in barely moist compost and start them into growth in a warm spot before planting out after your last frost. A stored root resprouts faster and flowers earlier than a fresh seed.
How to manage self-seeding and save your own seed
Four o’clocks reseed enthusiastically. In mild, frost-free regions that can tip into a nuisance, where they crowd out other plants and have naturalized in parts of the southern United States. In cold-winter gardens it is more of a happy surprise, with volunteer seedlings popping up once the soil warms.
To keep them in bounds, deadhead before the flowers set seed and pull volunteer seedlings while they are small. To welcome more plants, do the opposite and let some flowers ripen. Collecting your own seed is easy: wait until the spent bloom dries and a hard black seed forms at the stem tip, gather the seeds, dry them on a flat surface, and store them in labeled paper envelopes or jars to sow next spring. One caution for seed savers: four o’clocks cross-pollinate readily, so saved seed often shifts color from the parent over the years, which is part of the fun.
Common problems and how to fix them
Four o’clocks are among the most trouble-free flowers you can grow, and they are not favored by deer or rabbits, very likely because every part of the plant is toxic. Still, a few issues come up:
- Few or no flowers. Almost always too much shade or too much nitrogen. Move plants into more sun and cut back high-nitrogen feeding so energy goes to blooms, not leaves.
- Floppy, sparse plants. Leggy growth usually means low light or no pinching. Pinch young plants and grow them close together for mutual support.
- Yellowing leaves and collapse. The usual culprit is root rot from wet soil. Improve drainage, water only when the top inch is dry, and never let containers stand in saucers of water.
- Aphids or spider mites. Occasional, and worst on plants grown indoors or under stress. Check leaf undersides, hose pests off, or treat with insecticidal soap.
A word on safety: the roots and seeds are the most toxic parts, the plants can cause contact dermatitis on sensitive skin, and all parts are considered poisonous if eaten. If you have curious pets or small children who graze on plants, site four o’clocks where they cannot reach the seeds.
Cultivars and a few design ideas
If you want more than the standard mix, look for named selections. ‘Broken Colors’ and the ‘Marbles’ series produce striped, splashed, and marbled bicolor flowers; ‘Jingles’ is a small-flowered, multi-colored series; ‘Limelight’ pairs neon-pink blooms with chartreuse foliage; and ‘Salmon Sunset’ carries unusual pinkish-orange flowers. For something different, the related Mirabilis longiflora, the long-flowered four o’clock, bears white blooms with elongated throats and an orange-blossom scent.
For design, lean into the plant’s evening character. Four o’clocks are natural partners in a moon garden alongside moonflowers, night-blooming jasmine, and evening primrose, all of which open and release fragrance after dusk. They also make a charming “garden clock” with children: pair them with morning glories that open at sunrise, sunflowers that track the sun through the day, four o’clocks that open in the afternoon, and moonflowers that take over after dark, so something is always changing from dawn to nightfall. In a cottage border, their constant resupply of color through summer and into fall earns four o’clock flowers a spot worth saving room for.