HARDINESS: Winter hardy in Zones 7 to 10
PREFERRED SOIL pH: Adaptable
PREFERRED SOIL TYPE: Average
PREFERRED LIGHT: Sun to partial shade
ATTRIBUTES: Multicolored, fragrant flowers open in late afternoon; for beds
SEASON OF INTEREST: Summer to fall
FAVORITES: 'Jalapa Yellow' for yellow flowers; 'Broken Colors' for confetti colors
QUIRKS: Well-grown four-o'clocks are shrubby
GOOD NEIGHBORS: Petunias; other night-blooming annuals, such as flowering tobacco
WHERE IT GROWS BEST: Full sun to partial shade
POTENTIAL PROBLEMS: Japanese beetles
CRITTER RESISTANCE: Good
SOURCE: Seeds, tuberous roots
DIMENSIONS: 3 ft (1 m) tall, 30 in (76.2 cm) wide
Four-o'clocks in the Landscape
Although these care-free plants were popular garden staples until the 1950s, they fell out of style for several decades, perhaps because the flowers don't open until late afternoon and they close by the following morning. But today, many people don't get to enjoy their gardens until the workday is done, so the plant's late-day performance is no longer seen as a drawback. It's great to come home to the colorful, tubular flowers of four-o'clocks, which emit a heady scent o f sugar, lemon, and spice that varies from plant to plant.
The 2-4 ft (0.6-1.2 m) tall plants look festive grown in masses and more resemble leggy shrubs than annuals, making them suitable for use as a seasonal hedge. Even before the 2 in (5.1 cm) long blossoms emerge, the bright green leaves add a fresh accent to the landscape. The richly hued flowers combine well with magenta petunias or pink flowering tobacco, intensifying the colors.
A Carnival of Colors
Four-o'clock colors were once limited to yellow and magenta, and while four-o'clock flowers still tend to be mottled with those two colors, more choices are now available. An old variety that has been newly rediscovered is 'Broken Colors', which produces hundreds of 1-2 in (2.5-5.1 cm) long, trumpet-shaped flowers in colors including raspberry, orange, lemon yellow, and white, with some of the flowers being striped or dotted with several colors. Specialty nurseries often stock a solid yellow variety simply called 'JalapaYellow'.
Four-o'clocks are easy to grow from seed. In cold climates, start the seeds indoors 6 weeks before the last frost. Soak seeds in water overnight before sowing them on the surface of the soil. Keep the soil moist and at 70°F (21°C) until seedlings have several sets of adult leaves. Set seedlings out after danger of frost has passed, spacing them about 14 in (36 cm) apart in a sunny site with fertile, well-drained soil. Four-o'clocks will bloom the first season. In mild-winter climates, seeds can be sown outdoors in spring or at summer's end for flowering the following season.
Four-o'clocks grow as perennials in Zone 8 and warmer climates, and if undisturbed will form large tuberous roots. In colder climates, you can dig the tubers up in the fall after the first frost, the same way you would dig dahlias, and store the tubers in a dark, dry place that remains above 50°F (10°C) over winter. Plant the tubers outdoors in spring as soon as the ground warms. Saving tubers is a way to keep a favorite color year after year.
Because four-o'clocks have fleshy stems, they will wilt quickly if they're growing in dry soil. Water as needed during droughts to prevent wilting. Small and spindly plants may need fertilizer, which is easily provided by a monthly application of a balanced, soluble, all-purpose plant food, as directed on the package.
Pests are few but do include the metallic green Japanese beetle, which chews holes in blossoms for a few weeks in summer. Plants recover quickly when the beetles' feeding frenzy ends. Handpick beetles early in the morning, when they are sluggish, and drop them into a bowl of soapy water, or spray the plants with the biological insecticide neem, according to package directions. Apply the biological control milky spore to nearby lawns in spring to kill beetle larvae.