How to Plant and Grow Four O'Clock

Four o'clock has fragrant tubular-shaped flowers that come in various colors and patterns. Sometimes you even get blossoms of different colors on the same plant. These flowers open in the late afternoon, around 4 p.m. (hence the name), and close up again the following morning. Because it loves to self-seed, this classic cottage garden bulb can often be planted once and enjoyed for years. Use four o'clock to fill up space quickly as an annual in a mixed bed, or provide splashes of color in a container. Four o'clock is hardy in warm zones 8-11.

The roots and seeds of the four o’clock plant are considered mildly toxic to humans and pets. Wear gloves when handling the roots.

Where to Plant Four O'Clock

Plant four o’clocks in full sun and well-drained soil. If you can, situate this nighttime bloomer near a bedroom window to enjoy its fragrance during warm evenings. Mix four o’clock plants with other flowering plants to bring an old-fashioned cottage garden look to any bed or border with lots of sunlight and ample space for the blooms to spread (if you feel like letting them roam).

In warm climates, some types of four o'clock can be grown as a ground cover. When grown in this fashion, it can be mowed to ground level at the end of the season in October.

How and When to Plant Four O'Clock

Four o'clock is extremely easy to start from seeds (it will even self-seed in optimum conditions). Soak them in water overnight before planting to improve their odds of germinating. Plant seeds directly in the garden soil after the last frost date, or start plants indoors 6 to 8 weeks ahead of that date. If you prefer to work with seedlings or dormant tubers plant them outside after the last frost date.

If you are sowing seeds directly into the ground, place them 6 inches apart and cover them with just a 1/2 inch of soil. When seedlings emerge, thin them to about 12 to 18 inches apart. Transplanted seedlings should be planted 12 to 18 inches apart to allow for growth.

When planting a dormant tuber, dig a hole twice the size of the tuber and place it in the hole with the pointed end down. Holding it in place, cover your tuber with 1 to 2 inches of soil, tamping it down as you work. Space multiple tubers about 24 inches apart and water them thoroughly when you are finished planting.

Four O'Clock Care Tips

It's easy to care for four o'clocks. Regular watering and feeding are all they need, with an occasional pruning.

Light

Plant four o'clock in full sun. Many varieties will tolerate part shade but risk flopping over, thanks to this plant's ultimate large size and fast growth pattern.

Soil and Water

Four o'clocks grow in most soils but prefer well-drained, evenly moist soil with a slightly acidic pH. Water when the top 1 to 2 inches of soil are dry but prevent root rot by avoiding overwatering. Mulch around the plants to keep moisture in the ground. They're somewhat drought-tolerant.

Temperature and Humidity

Four o’clock plants are tender perennials, so they do not tolerate temperatures below 30 degrees Fahrenheit. In warmer climates, however, the tubers can be overwintered in the ground to come back in the next growing season.

Four o’clock plants are not fussy about air humidity but do require consistent, even soil moisture.

Fertilizer

If your soil lacks nutrients, fertilize four o'clocks once a month during the growing season. For the amount to use, follow product label directions. When planted in higher-quality soil, fertilizing is needed only once a year.

Pruning

Trim away faded flowers and shoots to keep plants looking healthy when the weather is dry. If you like, you can pinch off the main stem of the plant when four o'clock is young to encourage bushier growth. Pinch as close to the leaf nodes as possible, but do not damage the buds underneath. Ideally, when you do this, the plant will send out multiple new stems from the pinch point.

Potting and Repotting Four O'Clock

Four o'clocks are large plants, so don't do as well in containers as other plants do. Look for smaller varieties if you want to plant them in pots.

Pests and Problems

Part-shade conditions may lead to problems with powdery mildew. Look out for white or brown rust or leaf spot. Use preventive measures to keep fungus from growing, including tossing out affected plants and plant rotation.

How to Propagate Four O'Clock

There are two ways to propagate four o’clock plants from seed. First, you can simply allow the plants to reseed themselves and thin them out when seedlings emerge. Second, you can collect four o’clock seeds by plucking the dark, pea-sized seeds from the fading blooms. Remember to use caution when handling the seeds as they contain toxic compounds.

Dry your saved seeds in a cool location for several days and then place them in an envelope. Keep your packet of seeds in a cool, dry place until the following spring.

In spring—about 6 to 8 weeks before the last frost—soak your seeds in a bowl of water overnight. Prepare a tray or some grow pots with moist potting mix and sow the seeds about 1/4 inch deep. Position the pots in a warm (about 70 degrees) spot that gets at least 6 hours of sunlight each day and keep the soil evenly moist. Do not allow the soil to completely dry out. Once seedlings emerge, they should be hardened off for a week before they are transplanted outdoors.

Since four o'clock is a tender perennial that produces tuberous roots, it can also be divided much in the same way you would divide dahlias. Look for bulbous growth buds (or eyes) that branch from the original stem. Cut the tuber apart with a straight-edged sharp knife (not a serrated one). Each division needs a section of the original stem and an eye for successful division. Replant your divided tubers immediately to avoid shocking the plant.

In cooler climates, if you wish to bring back your four o’clocks the following spring, you will need to overwinter them by digging up the tuberous roots in the fall and storing them in a cool, dry place until planting time the following spring.

Types of Four O'Clock

'Limelight' Four O'Clock

Mirabilis 'Limelight' bears chartreuse foliage and bright magenta flowers on 2-foot-tall plants.

'Red Glow' Four O'Clock

This selection of Mirabilis bears vibrant red flowers on 2-foot-tall plants.

Four O'Clock Companion Plants

Cosmos

This cottage-garden favorite fills your garden with color all season. The simple, daisylike flowers appear in cheery shades on tall stems that are great for cutting. The lacy foliage makes a great backdrop for shorter plants, as well. Plant cosmos from seed directly in the ground in spring or start from established seedlings. Cosmos plants are hardy in zones 2-11.

Flowering Tobacco

There are several types of nicotiana, also called flowering tobacco because it's a cousin of the regular tobacco plant. Try the shorter, more colorful types in containers or the front of beds or borders. The taller, white-only types, which can reach 5 feet, are dramatic in the back of borders. And they're ideal for night gardens in zones 10-11; they're usually most fragrant at dusk.

Petunia

Petunias are vigorous growers and prolific bloomers from mid-spring through late fall. Color choices are nearly limitless, some with beautiful veining. Many are sweetly fragrant. Some also tout themselves as "weatherproof," meaning the flowers don't close up when water splashes them. Wave petunias have made this plant even more popular. Reaching up to 4 feet long, they're great as a groundcover or when cascading from window boxes and pots. Hardy in zones 10-11

Garden Plans for Four O'Clock

Moon Garden

There's no rule that says gardens are purely for daytime enjoyment. This garden plan, filled with night bloomers such as moonflowers, four o'clock, and angel's trumpets is at its best when the moon is high in the sky. Be sure to include a garden bench where you can bask in the sweet fragrances (that also attract nighttime pollinators like fireflies).