Four o'clocks (Mirabilis jalapa) are bushy flowering tender perennial plants, a long-standing garden favorite often grown as an annual outside its hardiness range (zones 7 to 10). Native to tropical South America, this tuberous-rooted plant produces slightly pointed oval leaves on multi-branching stems. Varieties include flowers in shades of white, yellow, pink, red, and magenta colors, as well as splashed/marbled blooms in orange and red. Occasionally, plants may produce flowers sporting different colors on the same plant. Four o'clocks can be expected to bloom from mid-summer all the way until frost.
The 2-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 bloom earlier in the day. This quick-growing plant often sprawls in the garden, and it looks best with a support. It is often used in mixed border gardens or in containers on decks and patios.
|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 tall and wide|
|Sun Exposure||Full sun to part shade|
|Soil Type||Tolerates a wide range of soils|
|Soil pH||6 to 7|
|Bloom Time||June through first frost|
|Flower Color||Pink, rose, red, magenta, yellow, white|
|Hardiness Zones||9 to 11|
How to Grow Four O'Clock Plants
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.
Since four o'clocks bloom in the late afternoon and evening, plant them where you’re sure to see them and catch a whiff of their lemony-sweet fragrance, such as around a patio. Grow them in pots on decks or plant them along walkways and on the edges of seating areas. They mingle and grow through other plants nicely, making a pretty underplanting. The plants typically grow 2 to 3 feet tall.
Sphinx moths and other noctural insects pollinate four o'clocks, but butterflies and hummingbirds will also adore four o'clock's late-afternoon tubular flowers. After the plant is done blooming in fall, the tuberous roots can be dug up and stored for winter, then replanted the following spring. Dig and store tubers much as you would dahlias: shake off soil, then place in a cool, dark location with temperatures above freezing.
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.
Any soil type will suffice, but rich, loamy, well-drained soil is ideal. The plant prefers neutral to slightly acidic pH levels.
Do not let these plants dry out; water whenever the top 1 to 2 inches of soil becomes dry. Also avoid overwatering, as soggy roots can be a problem. Mulching around the plants helps to keep the soil moist.
Temperature and Humidity
Mirabilis jalapa, also known as Marvel of Peru, prefers warm but relatively dry air conditions and moist soil.
Use an all-purpose organic fertilizer only if the plant's leaves are pale green. Do not over-fertilize, as the plant thrives on neglect!
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 with a light citrus scent that freely self-seeds.
- Mirabilis jalapa 'Jingles' produces small, multi-colored flowers.
- Mirabilis jalapa ''Kaleidoscope' flowers are multi-colored pink, yellow and white blooms with interesting splashes and streaks.
Toxicity of Four O'Clock Plants
The roots and seeds of four o'clocks are 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.
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 Four O'Clocks 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 monthly with a balanced 10-10-10 fertilizer.
Growing From Seeds
These plants can be sown directly in the garden in the spring when danger of frost has passed. For best germination, soak seeds overnight in water. Plant the seeds about 1/4 inch deep. If growing your own seedlings indoors, start them six to eight weeks before the last frost. Place them underneath a light source, as light boosts germination. 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 pulled and moved to another location if needed.
Common Pests and 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. On a positive note, some reports claim that the leaves of four o'clock plants are both attractive and lethal to Japanese beetles.