How to Grow Four O'Clock Plants

Four o' clock plant

The Spruce / Autumn Wood

Four o'clock plants (Mirabilis jalapa) are bushy flowering perennials. These tuberous-rooted plants produce slightly pointed oval leaves on branching stems. They get their common name because of the way they bloom. The flowers open in the late afternoon, typically around 4 p.m. or so, and then remain open until the next morning. The approximately 2-inch-long blooms are trumpet-shaped with five petals, and they come in several colors, often shades of pink and red. Some four o’clock plants produce flowers in multiple colors, sometimes with marbling or other markings. This is a fast-growing plant that often sprawls in the garden. It’s best planted in the spring.

Botanical Name Mirabilis jalapa (synonym:  Mirabilis lindheimeri)
Common Names Four o'clock plant, marvel of Peru, garden jalap
Plant Type Herbaceous, perennial
Mature Size 2–3 ft. tall and wide
Sun Exposure Full, partial
Soil Type Moist, well-drained
Soil pH Acidic, neutral
Bloom Time Summer, fall
Flower Color Pink, red, yellow, white
Hardiness Zones 9–11 (USDA)
Native Area South America
Toxicity Toxic to people and animals
Four o' clock flowers
​The Spruce / Autumn Wood

Four O'Clock Plant Care

Because four o'clock plants bloom in the late afternoon and evening, it's best to plant them where you’re sure to see them and catch a whiff of their lemony-sweet fragrance, such as around a patio. They grow well in garden beds or in container plantings, and they mingle and grow through other plants nicely, making a pretty underplanting.

Four o’clock plant maintenance is fairly simple. Expect to water your plants fairly regularly if you don’t have rainfall, and feed them throughout the growing season. They’ll also need a bit of pruning to keep them looking fresh and healthy. After the plant is done blooming in the fall, the tuberous roots can be dug up and stored for winter in a cool (but not freezing), dark location. Replant them the following spring once temperatures are reliably above freezing. If you live within the plant's growing zones, the tubers can stay in the ground for winter.

Light

Four o'clocks thrive in full sun, meaning approximately six hours of direct sunlight on most days. They will tolerate partial shade, though the plants might become somewhat leggy and not bloom as profusely in locations that are too shady.

Soil

These plants can grow in a variety of soil types. But rich, loamy, well-drained soil is ideal. And a neutral to slightly acidic soil pH is best.

Water

Do not let these plants dry out; water whenever the top 1 to 2 inches of soil becomes dry. But avoid overwatering, as soggy soil can cause root rot. Mulching around the plants can help to keep the soil sufficiently moist. Plants grown in containers will generally need more regular watering than those in the ground.

Temperature and Humidity

Four o’clock plants thrive in warm temperatures and are often grown as annuals in cooler climates outside of their growing zones, where the plants die once frost and cold fall temperatures arrive. Humidity typically isn’t an issue for them as long as adequate soil moisture is maintained. 

Fertilizer

Apply a balanced fertilizer in the spring, and continue to feed monthly until fall. However, if you already have rich soil, you might only need to give your plants the one spring feeding. 

Varieties of Four O'Clock Plants

There are several varieties of four o'clocks:

  • Mirabilis jalapa 'Alba' is a white variety with a light citrus scent that freely self-seeds.
  • Mirabilis jalapa 'Jingles' produces small, multicolored flowers.
  • Mirabilis jalapa 'Kaleidoscope' flowers are multicolored pink, yellow, and white blooms with interesting splashes and streaks.
All white four o'clock flower
MIXA / Getty Images
Mirabilis jalapa 'Kaleidoscope'

Anna Yu / Getty Images 

Are Four O'Clock Plants Toxic?

All parts of this plant, including the seeds, are poisonous both to people and animals. Toxicity can result from ingesting the plant or from skin contact.

Symptoms of Poisoning

Ingestion can cause stomach pain, nausea, vomiting, diarrhea, and lack of appetite. Skin contact can cause redness, rash, and pain. The symptoms are typically mild and resolve on their own, but it’s still wise to contact a medical professional as soon as possible if you suspect poisoning.

Pruning

Pinch back the main shoot when the plant is young to promote a bushier growth habit and more flowering. In dry weather, when the plants can get a little ragged looking, a shearing back by about a third will refresh them. Because four o’clocks bloom so profusely, keeping them deadheaded (removing spent blooms) is all but impossible, which is fine because they don’t really need it to keep blooming.

How to Grow Four O'Clock Plants From Seed

These plants can be sown directly in the garden in the spring once the danger of frost has passed. For best germination, soak the seeds overnight in water. Then, plant the seeds about 1/4 inch deep in your garden soil. You also can start seeds indoors roughly six to eight weeks prior to your area's projected last frost date. Plant them in a seed-starting mix about 1/4 inch deep, and place them by a light source. Keep the soil moist but not soggy as you wait for seedlings to appear.

Furthermore, chances are good that if you allow your plants to go to seed in the fall, they will self-seed in the garden, especially in warmer zones. Seedlings can be easily unrooted and moved to another location if you wish.

Common Pests/Diseases

Four o'clocks tend to be very pest- and disease-resistant. However, rusts (white rust and brown rust) and some leaf spot diseases can affect the foliage. The best solution for areas prone to rust bacteria is to follow integrated pest management practices, such as discarding affected plants, applying fungicide to stored tubers, and rotating plants from year to year.

Watch Now: 7 Tips for Every Gardener