Four O'Clock Plant Profile

Evening Blooms in Every Color

Four O'Clock Flowers (Mirabilis jalapa)

Anna Yu/Getty Images

Four o'clocks (Mirabilis jalapa) are bushy flowering perennial plants, a long-standing garden favorite often grown as an annual outside its hardiness range (zones 9 to 11). This tuberous-rooted plant produces slightly pointed oval leaves on multi-branching stems. It is an unusual plant, in that it may produce flowers of different colors on the same plant—including white, yellow, and a variety of pink, red, and magenta colors. Individual flowers may also feature a mixture of colors. The plant can be expected to bloom from mid-summer all the way until frost.

Botanical Name Mirabilis jalapa, Synonym: Mirabilis lindheimeri
Common Name Four o'clock, marvel of Peru, umbrellawort
Plant Type Herbaceous perennial
Mature Size 2 to 3 feet in height, similar spread
Sun Exposure Full sun to part shade
Soil Type Tolerates a wide range of soils
Soil pH 6 to 7 (neutral to slightly acidic)
Bloom Time June through first frost
Flower Color Pink, rose, red, magenta, yellow, white
Hardiness Zones 9 to 11 (USDA)
Native Area Peru
All white four o'clock flower
MIXA / Getty Images

How to Grow Four O'Clocks

Four o'clocks can be directly seeded into the garden or planted from nursery seedlings or tubers. They are heavy feeders, so rich, humusy soil is best; expect to feed them regularly in less ideal soils.

Keep four o'clocks moist. Mulch around the plants to keep the soil moist and the plants blooming. Feeding with an all-purpose fertilizer once a month will keep them blooming profusely. After the plant is done blooming in fall, the tuberous roots can be dug up and stored for winter, then replanted the following spring.

The two-inch-long flowers have five petals and are trumpet-shaped; they typically bloom in the late afternoon, from about 4:00 to 8:00 pm, although on cloudy days they may not bloom at all. This quick-growing plant often sprawls in the garden. It is often used in mixed border gardens, or in containers on decks and patios.

Since four o'clocks bloom in the evening, plant them where you’re sure to see them and catch a whiff of their fragrance. Place pots on decks or plant along walkways and on the edges of seating areas. They mingle and grow through other plants nicely, making a nice underplanting. Hummingbirds will visit your garden because they are attracted to four o' clock's tubular flowers.

Light

Four o' clocks thrive in full sun (six hours per day) but will tolerate part shade, although the plants may become somewhat leggy in shady locations.

Soil

Any soil type will suffice, but rich, loamy soil is ideal. The plant prefers neutral to slightly acidic pH levels.

Water

Do not let these plants dry out; water whenever the top one to two inches of soil becomes dry. Avoid overwatering, as soggy roots can be a problem.

Temperature and Humidity

Mirabilis jalapa is native to Peru. It prefers warm but relatively dry air conditions and moist soil.

Fertilizer

A monthly application of organic fertilizer will keep four o'clocks blooming vigorously. Less robust soils may require more frequent feeding.

Varieties of Four O' Clock

  • Mirabilis jalapa mix includes old-fashioned self-seeding four o’clocks in mixed solid colors.
  • Mirabilis jalapa Alba is a white variety that freely self-seeds.
  • Mirabilis jalapa Jingles cultivars are smaller plants with two-tone and multi-colored flowers.
  • Mirabilis jalapa Kaleidoscope is a hybrid with multi-colored pink, yellow and white blooms.

Toxicity of Four O' Clocks

The roots and seeds of four o' clocks are mildly toxic, causing skin irritation through contact, and stomach pain, nausea, vomiting, and diarrhea if ingested. Both humans and animals can be affected, though fatalities are almost unknown. Treatment is usually not necessary, but it is a good idea to keep children and pets away from these plants.

Pruning

Pinch back the main shoot when the transplant is young to promote a bushier plant and more flowering. In drier seasons, 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 is all but impossible, and they don’t really need it to keep blooming.

Growing in Containers

When planted in containers, four o' clocks require a large pot filled with general-purpose potting soil (not garden soil). Plants in containers will need more frequent watering and feeding than those in the garden. Feed twice monthly with a balanced 10-10-10 fertilizer.

Growing From Seeds

These plants can be sown directly in the garden just before the last frost of the winter or spring. Plant the seeds about a quarter-inch deep. If growing your own seedlings indoors, start them six to eight weeks before the last frost. Chances are good that if you allow your plants to go to seed in the fall, they will self-seed in the garden. Seedlings can be easily pulled and moved to another section

Common Pests

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. On a positive note, some reports claim that the leaves are both attractive and lethal to Japanese beetles.