How to Grow and Care for Four O'Clock Plants

Four o'clock plants (Mirabilis jalapa) are bushy blooming perennials in warm climates that are native to South America (they are also known as 'Marvel of Peru'). These tuberous-rooted plants produce slightly pointed oval leaves on branching stems and reach 2-3 ft. tall and wide. They get their common name because of the way they bloom. The flowers have a lemon scent and open in the late afternoon, typically around 4 p.m. or so, and then remain open until the next morning.

This is a fast-growing plant that often sprawls in the garden and thrives in full sun. It's important to note that all parts of four o'clock plants are toxic both to people and pets. Read on for our care guide.

Four O'Clock Plant Care

Here are the main care requirements for growing four o'clock plants:

• Keep consistently moist
• Thrives in full sun
• Hardy in zones 9-11
• Feed throughout the growing season
• Prune to keep looking fresh and healthy

Planting

Plant four o’clock plants container deep and 24 inches apart. Four o'clock plant seeds can be sown directly in the garden once frost has passed. If there is still a threat of frost, start 8 weeks before the last frost date indoors. Plant in full sun and well-draining, acidic soil. Soak the seeds overnight before planting to increase chances of germination.

Light

Plant four o'clock plants 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

Opt for rich, loamy, well-drained soil with a neutral to slightly acidic soil pH when planting your four o'clock plant for ideal conditions. However, these plants can grow in a variety of soil types.

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. Water every 8-9 days, however, during periods of extreme heat you'll want to water more frequently (every 2-3 days).

Temperature and Humidity

Consider your climate and planting location when planting four o'clock plants. 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, following product instructions, 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': 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 four o'clock plant is young to promote a bushier growth habit and more flowering. In dry weather, when four o'clocks may get a little ragged looking, shear them back by about a third to reinvigorate the plants.

Propagating Four O'Clock Plants

It's possible to propagate four o' clock plants by cuttings. Here's how:

1. Take a 3- to 6-inch-long cutting below a set of leaves, ideally when the plant is not currently in bloom.
2. Take off any bottom leaves, but leave a few at the top.
3. Apply a powdered or gel rooting hormone to the ends.
4. Plant in a small pot or planting tray with potting soil.
5. Keep the soil moist, but don't oversaturate as you'll risk root rot.
6. Until you start to see new growth, keep the cuttings out of direct sunlight. Indirect, dappled light is the best option.
7. Once you see new growth, you can transfer the cuttings to a bed or container.
   

How to Grow Four O'Clock Plants From Seed

Four o'clock plants can be sown directly in the garden in the spring once the danger of frost has passed.

1. For best germination, soak the seeds overnight in water.
2. Then, plant the seeds about 1/4-inch deep in your garden soil.
3. 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.
4. Keep the soil moist but not soggy as you wait for seedlings to appear.
5. When frost danger has passed and seedlings are sturdy, harden them off before planting in the garden.
   

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 Pests & 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

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. 

Bloom Months

Four o’clocks readily bloom each year starting around June and stretching all the way to frost in the fall.

What Do Four O'Clock Plants Flowers Look and Smell Like?

The tubular flowers have a lemony-sweet fragrance. 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 bicolor flowers, sometimes with marbling or other markings.

How to Encourage More Blooms

Providing sufficient light is typically the best way to get the most blooms out of your plant year after year.

Deadheading Four O'Clock Plants Flowers

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.

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 could 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 may still bloom overnight; you just don't 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.