How to grow four o'clock plants – for spectacular, sweet-smelling summer blooms that hummingbirds and butterflies adore

Four o'clock plants (Mirabilis jalapa) truly live up to their name. They got their moniker from the fact that their flowers don't open until late afternoon and last into the night. The plants are also known as the 'Marvel of Peru' due to their native origin in the Andes regions of South America.

They are tender perennials that produce bright, sweet-smelling tubular flowers in summer and fall. The spectacular blooms come in many colors, and you can even get multiple colors on a stem. They make great plants for pollinators, attracting hummingbirds, butterflies, and bees during the day, plus nocturnal pollinators after the sun goes down.

Four o'clock plants are simple, low-maintenance plants for flower beds or containers. You can grow them in most climates, as even though they are tender, they can be grown as annuals or lifted and overwintered in cooler climates, similar to dahlias. If you want to grow four o'clock plants, I spoke to some experienced gardeners to reveal their tips and tricks for sowing seeds and having happy and healthy four o'clock plants.

All you need to know to grow four o'clock plants

The easiest and most inexpensive way to grow four o'clock plants is to sow seeds in spring. Alternatively, you can propagate the plants by purchasing tubers or taking plant cuttings from established clumps.

Before growing four o'clock plants, it is important to recognize that they are toxic to both people and animals. If you worry about potentially poisonous plants in your yard, due to an overly curious pet, for example, steer clear of this plant.

How and when to plant four o'clock seeds

Four o'clock plants are simple flowers to grow from seed, but before you start sowing, they do need to be both scarified and soaked – it takes a bit more effort but is well worth it.

Juliet Howe, award-winning horticulturist and founder of Twigs Design, recommends both these steps, as they speed up germination and increase the number of seeds that will sprout.

'Mirabilis jalapa seeds have a hard outer coating,' she explains. 'Thinning or scarifying this seed coating will speed up germination by allowing water into the seed. To scarify a seed, either rub gently with a piece of sandpaper or, using a small blade, cut the seed, creating an entry point for water.

'Then, place the seeds in a bowl of lukewarm water for eight hours. This hydrates the embryo inside the seed, signalling that it’s time to begin growing.'

After completing the above steps, the seeds can be sown. In warmer climates, this can be done outdoors after the risk of frost has passed. In cooler zones with shorter seasons, starting seeds indoors 6-8 weeks before the last frost is advisable to give them a protected start and avoid any unexpected late frosts.

• To sow seeds indoors – Sow seeds on the surface of well-draining seed compost and give a light covering of more compost or vermiculite – but keep it thin as they need light for germination. Place the container in a bright spot where it can receive temperatures between 65 and 75°F. The seedling should appear in 7-14 days, and you can transplant the seedlings outside after the frost, after a period of hardening off.
• To sow seeds outdoors – Once the soil temperature reaches at least 65°F, sow seeds directly into their growing position a quarter inch deep in the soil and at least six inches apart. Gently cover them with a thin layer of soil and keep them moist for good germination. Thin the seedlings as they develop to 18-24 inches apart to give plants adequate space to grow.

Juliet Howe

Juliet Howe is an award-winning horticulturist and the founder of Twigs Design. For more than two decades she has helped beautify the homes, gardens, and communities of Fairfield County, CT.

Where to grow four o'clock plants

Four o'clocks do best in full sun; they are a sun-loving flower that does its best blooming planted in a sunny spot in the yard. However, in very hot climates, they may benefit from some protection from the intense afternoon sun.

'Four o'clocks can take some shade,' claims Edwin Dysinger from Seedtime. 'As long as they have at least six hours of full sun each day, they'll bloom well.'

On an ideal location for four o'clocks, Edwin adds: 'They don't require a special soil and can do well in poor soils, but they will do best in a neutral to slightly acidic soil.'

The truth is that four o'clock plants can prosper in a variety of soil types, provided the drainage is sufficient.

'While four o'clock plants need water to thrive, their tubers will rot if they are in waterlogged soil,' says Juliet. 'Choose a site where the soil is well-drained, or amend the soil accordingly.'

Such amendments to improve the garden soil include adding organic matter, such as compost, well-rotted manure, or leaf mold, to boost drainage and provide essential nutrients to plants.

Edwin Dysinger

Edwin Dysinger is a farmer, gardener, and co-founder of Seedtime, a visual garden planning app designed to make growing easier and more efficient. Drawing from years of hands-on experience, Edwin is passionate about helping others simplify their gardening journey with tools built by growers, for growers.

How to grow four o'clock plants – maintenance tips

• Watering – The key with four o'clock plants is consistency; the soil wants to be moist but not waterlogged, especially if you want the best flowers. 'If the top inch of the soil is dry to the touch, it is time to water,' says Juliet. 'During summer's hottest days, this may be at least every other day. In early fall, this may drop to once or twice a week.' Keep a close eye on when to water plants, but avoid overwatering as four o'clocks can suffer from root rot in waterlogged soils. Consider using a soil moisture meter to judge when your plants need moisture and avoid making the watering mistake of over-saturating the soil.
• Feeding – If you are fortunate enough to have rich, fertile soil, extra feeding may not be essential. Plants will benefit from an application of an organic balanced fertilizer in the spring, followed by feeding with a bloom booster in midsummer. One fertilizing mistake to avoid is continuing to feed past summer, as Juliet warns: 'Stop fertilizing in the fall. You'll want your plant to put its energy into its tuber, shutting down for the season rather than sending up new growth.'
• Pruning – Edwin recommends 'pinch back or trim young shoots to make them more bushy'. This is best done when the plant is young, around six inches tall, and beneficial as pinching out plants promotes bushier growth and increased flowering. The flowers of four o'clock plants themselves are short-lived and not self-shedding. Deadheading isn't essential, but it is recommended to tidy the plant, encourage more flowers, and have a longer blooming season. Deadheading also prevents the plant from self-seeding around the garden.
• Overwintering – Four o'clocks are fully hardy in zones 9-11. If you live in the US hardiness zone 8, you can attempt to overwinter tender plants by adding two inches of protective mulch before the first freeze. For gardeners in cooler climates with cold winters, you can lift the tubers to store for winter. Simply cut back the plant, lift the tubers, and, like with overwintering dahlias, store them in a dry, cool, frost-free place. If you aren't fussed about overwintering four o'clocks, you can treat them as an annual and remove them once the frosts kill the plant.

FAQs

Can you plant four o'clock seeds in the fall?

No, fall is not an ideal time to plant seeds. If you want to grow four o'clock plants from seed, stick to sowing in spring, either outdoors after your last frost or indoors 6-8 weeks before the final frost for your location.

How do you collect seeds from four o'clocks?

Four o'clocks are self-seeding flowers. You can prevent this by deadheading, or embrace it and get new plants for free. Either let nature do its course, or collect seeds before the plant disperses them. Four o'clocks produce large black seeds at the tips of the stems. You want to pick them and lay them out on a flat surface to dry, before storing the seeds in paper envelopes or glass jars to sow next spring.

As mentioned earlier, four o'clock plants flower into the night and make great plants for nocturnal pollinators. If you are looking for more plants that bloom at night, the likes of moonflowers, night-blooming Jasmine, and evening primrose all make fantastic choices. They are perfect if you want to create a moon garden to be enjoyed after dusk by humans and pollinators alike.