How to Grow and Care for Four O Clock Plants

The common name of four o’clocks was given to Mirabilis jalapa because the flowers of this plant do not open until late in the day. This old-fashioned garden ornamental in the four-o’clock family (Nyctaginaceae) is a tender perennial hardy in Zones 7-10, generally grown as an annual throughout most of the US. Native to tropical South America in the Andes – and also sometimes called Marvel of Peru – it is the most commonly grown ornamental species of Mirabilis. Discovered by Europeans in 1540, the root was used by indigenous peoples for medicinal purposes, as a hallucinogen, and as a purported aphrodisiac, while the flowers produce an edible red dye for coloring food.

The shrub-like, erect and spreading, multi-branched plants grow 2-3 feet tall and wide. The weak and brittle stems break easily and flop over if not supported. They are light or bright green but may have a yellow or pink hue. The opposite, ovate, bright green leaves are up to 4 inches long with a pointed end.

They are triangular to egg-shaped to lance-shaped, with smooth (non-toothed) edges. The plants produce elongated, dark-colored, swollen to tuberous taproots that can be a foot or more long and weigh up to 40 pounds in climates where they are perennial.
Flowers are produced in bright and pastel shades of white, yellow, pink, magenta, and red. Flowers of different colors can be found on the same plant – either simultaneously or at different times – and flowers may even be bicolored, speckled, or variegated.

They bloom in summer through fall and may have a strong, sweet-smelling fragrance when open (but sometimes have no noticeable scent). Flowers are borne in terminal or axillary clusters of one to several flowers. The colorful, trumpet-shaped portion of the flower is the pigmented calyx or partially fused sepals; the flowers actually have no petals. Each flower is about two inches long and abruptly flares out to about an inch across at the end with five lobes. These tubular flowers open late in the day or in the evening (although they will open earlier open earlier on rainy or very cloudy afternoons) as they are pollinated by sphinx moths (family Sphingidae) and other nocturnal pollinators with long tongues. Hummingbirds and butterflies are also attracted to the flowers.

The flowers wilt by the following morning and those faded flowers are not self-shedding, remaining on the plant – so some people may not like the appearance. Numerous large, dark, leathery, 5-ribbed, spherical “seeds” (actually a fruit that is a nut-like achene) with a wrinkled surface are produced in the fall. These are poisonous if ingested. They can also self-seed under the right conditions and have become naturalized in some parts of the southern U.S.

Grow four o’clocks in full sun in almost any type of soil but they do best in a humus-rich, well-drained spot. Plants can be started from seed sown outdoors after the danger of frost has passed or indoors up to 8 weeks ahead of time. Soaking the seeds in water overnight will speed up germination. Sow the seeds no more than ¼ inch deep as light aids germination. They should germinate in 1-3 weeks. Transplant seedlings when large enough to handle, if needed, into individual. Thin seedling or place transplants 12-24 inches apart.

As these are tender plants, put transplants outside after all risk of frost, about the same time you would plant tomatoes. Provide moderate moisture and fertilize periodically for the best growth. They have few pests and are not favored by deer. Tubers can be dug in the fall to store indoors and plant again in spring after the last frost. Treat the tubers like dahlias by digging them before the first freeze, shaking off the soil and storing them in dry, cool but frost-free conditions.

This sturdy plant can be used as an annual hedge if planted close together. They are right at home in a cottage garden, in borders and beds, or can be added to large containers. If possible place them along on lighted walkways where the night-blooming flowers and fragrance can be appreciated. They combine nicely with Asiatic lilies, creating an interesting contrast of large and small flowers.
There are some cultivars and hybrids of four o’clocks, although they are often offered just as ”Four O’Clocks”.

Four O’Clocks, Mirabilis jalapa

The common name of four o’clocks was given to Mirabilis jalapa because the flowers of this plant do not open until late in the day. This old-fashioned garden ornamental in the four-o’clock family (Nyctaginaceae) is a tender perennial hardy in Zones 7-10, generally grown as an annual throughout most of the US. Native to tropical South America in the Andes – and also sometimes called Marvel of Peru – it is the most commonly grown ornamental species of Mirabilis. Discovered by Europeans in 1540, the root was used by indigenous peoples for medicinal purposes, as a hallucinogen, and as a purported aphrodisiac, while the flowers produce an edible red dye for coloring food.

The shrub-like, erect and spreading, multi-branched plants grow 2-3 feet tall and wide. The weak and brittle stems break easily and flop over if not supported. They are light or bright green but may have a yellow or pink hue. The opposite, ovate, bright green leaves are up to 4 inches long with a pointed end.

They are triangular to egg-shaped to lance-shaped, with smooth (non-toothed) edges. The plants produce elongated, dark-colored, swollen to tuberous taproots that can be a foot or more long and weigh up to 40 pounds in climates where they are perennial.
Flowers are produced in bright and pastel shades of white, yellow, pink, magenta, and red. Flowers of different colors can be found on the same plant – either simultaneously or at different times – and flowers may even be bicolored, speckled, or variegated.

They bloom in summer through fall and may have a strong, sweet-smelling fragrance when open (but sometimes have no noticeable scent). Flowers are borne in terminal or axillary clusters of one to several flowers. The colorful, trumpet-shaped portion of the flower is the pigmented calyx or partially fused sepals; the flowers actually have no petals. Each flower is about two inches long and abruptly flares out to about an inch across at the end with five lobes. These tubular flowers open late in the day or in the evening (although they will open earlier open earlier on rainy or very cloudy afternoons) as they are pollinated by sphinx moths (family Sphingidae) and other nocturnal pollinators with long tongues. Hummingbirds and butterflies are also attracted to the flowers.

The flowers wilt by the following morning and those faded flowers are not self-shedding, remaining on the plant – so some people may not like the appearance. Numerous large, dark, leathery, 5-ribbed, spherical “seeds” (actually a fruit that is a nut-like achene) with a wrinkled surface are produced in the fall. These are poisonous if ingested. They can also self-seed under the right conditions and have become naturalized in some parts of the southern U.S.


Grow four o’clocks in full sun in almost any type of soil but they do best in a humus-rich, well-drained spot. Plants can be started from seed sown outdoors after the danger of frost has passed or indoors up to 8 weeks ahead of time. Soaking the seeds in water overnight will speed up germination. Sow the seeds no more than ¼ inch deep as light aids germination. They should germinate in 1-3 weeks. Transplant seedlings when large enough to handle, if needed, into individual. Thin seedling or place transplants 12-24 inches apart.

As these are tender plants, put transplants outside after all risk of frost, about the same time you would plant tomatoes. Provide moderate moisture and fertilize periodically for the best growth. They have few pests and are not favored by deer. Tubers can be dug in the fall to store indoors and plant again in spring after the last frost. Treat the tubers like dahlias by digging them before the first freeze, shaking off the soil and storing them in dry, cool but frost-free conditions.

This sturdy plant can be used as an annual hedge if planted close together. They are right at home in a cottage garden, in borders and beds, or can be added to large containers. If possible place them along on lighted walkways where the night-blooming flowers and fragrance can be appreciated. They combine nicely with Asiatic lilies, creating an interesting contrast of large and small flowers.
There are some cultivars and hybrids of four o’clocks, although they are often offered just as ”Four O’Clocks”.

• ‘Broken Colors’ – has flowers splashed or marbled in orangey-red
• ‘Jingles’ is a series with small, multi-colored flowers.
• The related M. longiflora has white flowers with an orange-blossom scent.

– Susan Mahr, University of Wisconsin – Madison

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How to Grow and Care for Four O’Clock Plants

Marie Iannotti is a life-long gardener and a veteran Master Gardener with nearly three decades of experience. She’s also an author of three gardening books, a plant photographer, public speaker, and a former Cornell Cooperative Extension Horticulture Educator. Marie’s garden writing has been featured in newspapers and magazines nationwide and she has been interviewed for Martha Stewart Radio, National Public Radio, and numerous articles.

Julie Thompson-Adolf is a Master Gardener and author with over 30 years of experience in year-round organic gardening; seed starting, growing heirlooms, and sustainable farming.

Four o’clock plants (Mirabilis jalapa) are bushy blooming 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.

It’s important to note that all parts of four o’clock plants are toxic both to people and pets.

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.

Types of Four O’Clock Plants

There are several types 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 with interesting splashes and streaks.

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.

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 uprooted and moved to another location if you wish.

Overwintering

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.

Common Plant 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.

How to Get Four O’Clock Plants to Bloom

Four o’clocks readily bloom each year starting around June and stretching all the way to frost in the fall. The tubular flowers have a lemony-sweet fragrance. 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. Providing sufficient light is typically the best way to get the most blooms out of your plant year after year.

Common Problems With Four O’Clock Plants

Four o’clock plants are generally healthy when grown in conditions they like. However, some common issues can arise in subpar environments.

Curling Leaves

Both pests and diseases can cause curling leaves on a plant. Aphids are a common culprit of curling leaves on four o’clocks, as these tiny insects suck the sap out of the leaves. They often can be knocked off the plant with a strong stream of water from a hose, or you can use insecticidal soaps.

Plant Not Blooming

If your plant doesn’t seem to be blooming at all, heat might be the reason. While four o’clocks generally bloom around 4 p.m., they might wait until later in the evening if the weather is extremely hot. So your plant might still bloom overnight; you just might not see it. Very nutrient-poor soil also can result in sparse blooms. Have a soil test done to make sure your soil has enough phosphorus, which aids in flowering.

This plant gets its common name because its blooms open in the late afternoon, or around 4 p.m. They stay open until the next morning.

Feeding and watering four o’clock plants is straightforward and not time-consuming. The plants also require minimal pruning.

Four o’clock plants grow and spread quickly under optimal conditions.

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1. Four O’clock. Utah State University Extension Office.
2. “Michigan Humane.” Michigan Humane Society.