Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
I love planting different kinds of flowers so that I have color in my garden from very early spring until late in the fall. During the summer, I grow flowers so that I have blooms all day from early in the morning (morning glories) until late at night (moon flowers). For a little pick me up after work, I grow four o’clocks which open late in the afternoon.
What are Four O'Clocks?
Four O’Clocks (Mirabilis jalapa) are herbaceous perennial flowering plants that are native to Peru. They are also called Marvel of Peru. The Aztecs grew them for medicinal purposes as well as for their beauty. The tubers were reputed to be both an aphrodisiac and to have hallucinogenic properties. The flowers produce an edible red dye which was used as a food coloring. In modern times, the dye from the flowers is used to color cakes and jellies.
The plants are called four o’clocks because the flowers open between 4 pm and 8 pm. They remain open all night emitting a lovely fragrance then close in the morning. New flowers open the following afternoon. The reason that the plants bloom at night is because its pollinators, which include sphynx moths and hawk moths, are active at night. The moths follow the scent to the flowers then use their long tongues to get to the nectar at the bottom of the long throats of the trumpet shaped flowers.
Four o’clocks are hardy in zones 7 – 10. In colder climates they are grown as annuals or at the end of the season the tubers are be dug up and stored indoors during the winter like dahlia tubers. They are then replanted in the spring.
The plants are quite large, growing 2 to 3 feet tall and wide. The stems are very brittle so you should give them some support. They grow from a tuber that can be as long as 12 inches and weigh as much as 40 pounds in areas where the plants are perennial.
The flowers are trumpet shaped with five petals. They come in pink, yellow and white. My favorite four o’clocks, and the only ones that I grow, are called Broken Colors with flowers that are bicolor with stripes and blotches. They make a colorful border in my flower bed. Bloom time is summer through fall. When they open in the late afternoon, the flowers will often attract hummingbirds.
After the flowers close in the morning, they will fall off of the plants. If they have been pollinated, you will find a green seed where the flowers were. The seeds mature to a brown color. Both the seeds and the tubers are poisonous. If ingested, they cause nausea, vomiting, and diarrhea.
How to Grow Four O'Clocks in Your Garden
Choose a sunny spot in your garden. The plants do best in full sun. They can take a little shade but have a tendency to get tall and leggy and fall over in the shade. They like rich, well-drained soil. Don’t let these beauties dry out. They like moist soil but not soggy soil which will cause their tuber to rot. Be sure to water before the top two inches of soil has dried out, about 1 inch of water per week. Fertilize monthly with a balanced fertilizer.
As the growing season progresses, your plants may start to look a little ragged, especially if you haven’t been deadheading them. Just like your petunias, it’s a good idea to prune them back by a third midway through your growing season to keep them looking great and growing vigorously.
How to Grow Four O'Clocks in Containers
Four o’clocks can be grown in containers. Just remember that containers need to be watered more often because they dry out quickly. You will also need to use more fertilizer because every time you water, nutrients leach out of the soil and drain out through the drainage hole with the water. Fertilize your containers twice a month with a balanced fertilizer. If you are using potting soil that has slow release fertilizer already in it, you will not need any additional fertilizer.
How to Store Then Plant Four O'Clock Tubers
If you live north of zone 7 and don’t want to keep buying four o’clock seeds or you have plants whose flowers you really like, you can dig up the tubers in the fall and replant them in the spring just like you do for your dahlias.
In the fall before your first frost, carefully dig up the tubers from your garden. If you wait until after a frost, the low temperatures will kill both the plants above ground and the tuber below ground. Cut the top vegetation from the tubers and brush the soil off of them but don’t wash them. If you store the tubers after they get wet, they will rot. Store the tubers somewhere dry and cool that will not freeze over the winter.
In the spring, after the last frost, you can replant your tubers. Dig holes that are twice as wide as the tubers and one inch deeper. You want the growing tip to be one inch deep. Space your holes 24 inches apart. Place a tuber in each hole with the pointed, root end at the bottom of the hole. The rounded growing tip should be facing upwards. Fill in the soil around and on top of the tubers making sure that the growing tip is only one inch below the soil. Then water well. Make sure the soil remains moist for the first two weeks after they are planted as they get acclimated to their new home. After two weeks, give them 1 inch of water (or rainwater) every week.
How to Grow Four O'Clocks From Seed
Most gardeners grow four o’clocks from seed. You can direct sow them in your garden after your last frost or start them indoors 6 to 8 weeks before your last frost. Whether you are starting them indoors or outdoors, it will help germination if you soak the seeds overnight before planting. This will soften the hard seed coat to make germination easier. Then plant the seeds ¼ inch deep. Germination should occur in 1 to 3 weeks. If grown outdoors, thin your seedlings to 12 to 24 inches apart. If grown indoors, transplant your seedlings after your last frost into your garden when the soil has warmed spacing them 12 to 24 inches apart.
In my NJ zone 6 garden, I transplant my tropicals the last week in May/first week in June. Any earlier, and the soil is still cold. Tropical plants will not grow in cold soil.
How to Save Seed From Four O'Clocks
Four o’clocks are one of the easiest plants from which to save seed. When the flowers have finished, they drop from the plant. If you look at the stem where they were, you will a green seed starting to form. Keep an eye on those seeds and when they have matured to a dark brown, simply use your finger to scoop them out. Spread the seeds in a single layer on a paper plate or paper towel and dry them for about for about a week someplace that is cool, dry and out of the sunlight. I use the top of my refrigerator.
Questions & Answers
Question: Can I grow them in sandy soil in Florida?
Answer: Sandy soil does not have enough nutrients in it and drains too quickly. Either add some compost and peat moss to your soil which will add nutrients and hold water or grow four o'clock in raised beds filled with rich loamy well-drained soil. You can also try growing them in containers using standard potting soil.
© 2020 Caren White
Caren White (author) on February 05, 2020:
Thank you. I'm glad that you found it helpful.
Umesh Chandra Bhatt from Kharghar, Navi Mumbai, India on February 05, 2020:
Excellent article. Well presented.