How to Grow and Care for 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.

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

Common Name Four o'clock plant, marvel of Peru, garden jalap
Botanical Name Mirabilis jalapa (synonym: Mirabilis lindheimeri)
Family Nyctaginaceae
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, USA
Native Area South America
Toxicity Toxic to people, toxic to pets

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 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.

Four o' clock flowers
​The Spruce / Autumn Wood

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.
All white four o'clock flower
MIXA / Getty Images
Mirabilis jalapa 'Kaleidoscope'
Anna Yu / Getty Images 

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 unrooted 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.

FAQ
  • Why is it called a four o'clock plant?

    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.

  • Are four o'clock plants easy to care for?

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

  • How fast do four o'clock plants grow?

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

Article Sources
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  1. Four O’clock. https://extension.usu.edu/rangeplants/forbsherbaceous/four-oclock.

  2. “Michigan Humane.” Michigan Humane, https://www.michiganhumane.org/.