Four o'clocks are one of those old-fashioned flowers I never get tired of. On hot July evenings, when so many plants look spent and sulky, these cheerful bloomers begin their daily show just as the light softens, opening their trumpet-shaped flowers and releasing that sweet, unmistakable fragrance. If you want them performing reliably every evening through late summer, July is the month that makes the difference.
I’ve grown four o'clocks in borders, gravelly side beds, and even in those awkward dry spots near the patio where other plants complained, and I can tell you they respond brilliantly to a few timely jobs. Below are the July tasks I would prioritize to keep plants vigorous, encourage heavier flowering, and make sure that lovely dusk scent carries right across the garden.
1. Water deeply, not little and often
By July, four o'clocks are usually growing fast and setting plenty of buds, so shallow watering just won’t do much good. I aim to soak the root zone to a depth of at least 6 to 8 inches, which usually means giving established plants around 1 inch of water per week, and closer to 1.5 inches if temperatures are consistently above 85°F. In practical terms, that is often 2 to 3 gallons per mature clump every 5 to 7 days in open ground, depending on your soil.
If your soil is sandy, you may need to water every 3 to 4 days. In heavier loam or clay, once a week is often enough. The best test is to push a finger or a trowel into the soil: if it is dry 2 inches down, water. Try to do it early in the morning so moisture is available through the heat of the day and the foliage dries quickly.
2. Mulch around the base to hold moisture
One of my favorite July shortcuts is adding a 2-inch layer of mulch around each plant. Four o'clocks cope with summer heat fairly well, but mulching cuts down stress dramatically and helps keep flower production steady. Use shredded bark, leaf mold, compost, or even clean straw, keeping the mulch about 1 inch away from the stems so they are not sitting in damp material.
A 2-inch mulch layer can lower moisture loss enough that you may water less frequently, especially during windy weather. It also helps stop the soil surface from baking hard, which matters if your plants are in full sun. I’ve noticed that mulched plants stay lusher by evening, and they rebound far better after a hot spell.
3. Feed lightly with a low-nitrogen fertilizer
In July, I avoid heavy feeding because too much nitrogen gives you lots of leaf growth and fewer flowers. What you want is a light application of a bloom-supporting fertilizer, something like a 5-10-10 or 4-6-4. Apply at half the label rate if your plants already look healthy, because four o'clocks are not especially greedy feeders.
As a guide, granular fertilizer might be applied at roughly 1 to 2 tablespoons around a mature plant, scratched lightly into the top inch of soil and watered in well. If you prefer a liquid feed, use it every 10 to 14 days at a diluted strength. I’ve had excellent results with a seaweed-and-tomato-feed routine used sparingly, especially in containers where nutrients wash out faster.
4. Deadhead spent flowers and remove seed set if you want more bloom
Four o'clocks are generous plants, but if they begin putting too much energy into seed production, flower numbers can slow. The flowers are small and short-lived, so I do not obsess over removing every faded bloom, but once or twice a week in July I go over the plants and pinch off spent clusters and any developing black seeds I do not want.
This tidying usually takes only 5 to 10 minutes for a few plants, yet it keeps them looking fresh and often encourages another flush of buds. If you want them to self-sow, leave some seeds later in the season. In July, though, I focus on bloom production first.
5. Thin crowded stems for better air flow
By midsummer, four o'clocks can become surprisingly dense, often reaching 2 to 3 feet tall and nearly as wide. That lush growth is lovely, but crowded stems trap humidity and shade the center of the plant. If yours are looking congested, remove a few weaker or inward-growing shoots at the base.
I generally thin no more than 10 to 15 percent of the growth at one time. The goal is not to make the plant sparse, just to open it enough that light and air can move through. This simple step can reduce mildew problems in humid regions and helps the plant direct energy into strong outer stems and fresh buds.
6. Check that they are getting enough sun
Four o'clocks will tolerate some light shade, particularly in very hot climates, but in July they flower best with at least 6 hours of direct sun a day. If they are growing in less than that, you may get plenty of leaves but a weaker evening display. Take a day to observe the area properly, because nearby shrubs or fast-growing annuals can cast more shade than you realized back in May.
For container-grown plants, this is an easy fix: move the pot into a brighter spot. For plants in the ground, trim back neighboring growth if possible. Even gaining an extra 2 hours of sun can noticeably improve bud count over the next couple of weeks.
7. Stake floppy plants before they collapse
After rain or irrigation, lush July growth can get heavy, especially if plants are in rich soil. I like to support them before they splay out across the border. Use three or four slim bamboo canes around the clump and loop soft twine or plant ties around the outside about 12 to 18 inches from the ground.
You do not need to bind them tightly. A loose corral is enough to keep stems upright while still looking natural. This matters more than people think, because flowers held upright are more visible, less likely to be splashed with soil, and easier for evening pollinators to find.
8. Watch for spider mites, aphids, and caterpillar damage
Four o'clocks are fairly easygoing, but hot, dry July weather can bring spider mites, especially if plants are stressed. Look for pale speckling on leaves, fine webbing, or foliage that seems dull and dusty. Aphids may gather on soft new growth, while caterpillars can chew ragged holes overnight.
I inspect the undersides of leaves every few days. A strong spray of water often clears light aphid infestations. Spider mites usually improve when plants are watered properly and foliage is hosed down in the morning every few days during a dry spell. If damage is heavier, insecticidal soap can help, but always spray in the cool part of the day and follow the label exactly.
9. Weed the root area so the plants are not competing
July weeds steal exactly what your four o'clocks need most: water, nutrients, and space. I keep a weed-free circle at least 12 inches around each plant, wider if the clump is large. This is especially important with fast-growing summer weeds like crabgrass, pigweed, or chickweed in milder regions, because they can crowd younger plants quickly.
Pull weeds after rain or after watering when the soil is soft, and try not to disturb the roots too deeply. A hand hoe used gently over the top 1 inch of soil is usually enough. Once you weed and mulch, maintenance becomes much easier for the rest of the month.
10. Harvest a few flowers in the evening and enjoy the scent close up
This may sound indulgent, but I genuinely think it is part of growing them well: spend time with the plant at the hour it is meant to shine. Four o'clocks often begin opening in late afternoon, typically between 4 p.m. and 6 p.m., depending on cloud cover, temperature, and your local conditions. That is the best time to notice whether flowering is abundant, whether buds are forming properly, and whether fragrance is strong.
If you cut a few stems for a small jar on an outdoor table, do it in the evening with clean snips and place them straight into water. They are not long-lasting cut flowers, but they are delightful for a short twilight display. More than once, I’ve caught a watering issue or pest problem simply because I made a habit of checking them at the same hour each day.
11. Feed container-grown plants more often than those in the ground
If your four o'clocks are in pots, July care needs to be more hands-on. Containers heat up faster, dry faster, and lose nutrients faster. A 12- to 16-inch pot in full sun may need watering once a day during a heatwave, and sometimes twice a day if temperatures climb above 90°F and the plant is root-filled.
I feed potted plants with a diluted liquid fertilizer every 7 to 10 days, rather than relying on a single granular feed. Make sure the pot has good drainage, and never let it stand in a saucer full of water for hours on end. Healthy container plants can bloom just as generously as those in the ground, but they need more regular attention.
12. Mark the best plants now if you want to save seed or lift tubers later
July is an excellent month to decide which four o'clocks have earned a place next year. If one plant has especially vivid magenta flowers, stronger fragrance, better branching, or superior drought tolerance, mark it with a tie or plant label now. By early autumn, it is easy to forget which clump performed best.
If you garden in a colder region where tubers are lifted before winter, that note will be useful later. If you save seed, let a few of the healthiest flowers mature toward the end of the season. I always find that a little selection from year to year improves the display, and it costs absolutely nothing.