WateringTimesWatering plan, $19
Mirabilis jalapa, WUCOLS IV

How often to water four o'clock in California

In July in the Central Valley, established four o'clock in loam needs a deep watering about every 14 days: about 1.5 gallons each time for a plant 2 feet across, about 0.8 gallons a week. Four o'clock grows from a fleshy tuber into a rounded mound of dark green leaves, with fragrant trumpet flowers that open in late afternoon and close by morning. It has moderate drought tolerance, though its California water rating rises in the deserts. It self-sows readily and can spread beyond where it was planted if seed pods are left to mature.

PerennialRated for 6 of 6 zones

How often to water four o'clock, month by month

Your city
Plant width
2 ft
Your soil

Type your city above and the days between waterings and the gallons appear here, worked out from your city's climate table. Or read the figures by climate zone further down.

Every month, on your water days. The personal plan prints this for four o'clock and the rest of your yard, on the days your water supplier allows.Get the plan for $19

How this is worked out: established roots fill the top 1 foot of soil, and you water again when that soil has dried halfway. Loam soil holds about 1.5 inches of water per foot. Water the whole area the plant covers, and skip a watering after a good soaking rain.

Which soil do you have?

Dig down a few inches, take a handful of moist soil and squeeze it.

  • Sandy: gritty, falls apart when you open your hand, will not form a ball.
  • Loam: forms a soft ball that crumbles when you poke it.
  • Clay: forms a firm, sticky ball and squeezes out into a ribbon between thumb and finger.

Still not sure? Pick loam. Most garden beds sit between sand and clay.

How to measure plant width

A shrub with its width marked from one side to the other and the circle under it shaded blue

Measure across the plant, from the tips of the leaves on one side to the tips on the other.

Water the whole area the plant covers, shown in blue. The gallons here cover that area.

A wider plant means more gallons each watering, not more waterings. While it is young, measure again each spring.

How to tell it needs water

  • Soil dry a few inches down around a leafy mound signals that four o'clock needs a soak during active growth
  • Wilting four o'clock leaves call for checking root-area moisture before deciding whether afternoon heat requires more water
  • Fewer open four o'clock flowers warrant checking the time of day as well as the plant's growing conditions
  • Yellowing four o'clock leaves over persistently soggy soil warrant a drainage check before another soak
  • A collapsing four o'clock crown needs inspection rather than an automatic increase in irrigation

How to water it

  • Water the mound at soil level, soaking down to where the fleshy tuber sits below the crown
  • Let the top few inches of soil dry between waterings once the plant has filled out
  • Use well-drained soil, since the tuber fares poorly sitting in water for long stretches
  • Spread a light mulch layer around the base to slow moisture loss without burying the crown
  • Widen the watered area as the mound grows and self-sown seedlings fill in nearby ground

Through the seasons

A newly planted four o'clock needs regular moisture while its tuber and root system establish through the first growing season. Established plants have some drought tolerance, but desert gardens carry a higher water rating than coastal ones. Growth and flowering run from late spring into fall, with frost cutting back the top growth where winters turn cold. Winter rain can help where this plant stays dormant in the ground, though it needs little moisture at that stage either way. WUCOLS rates four o'clock very low water on the north-central coast and on the south coast. It rates low water in the Central Valley and South Inland, and moderate water in the high desert and the low desert.

In pots

Four o'clock grows well in a container with its tuber given room to bulk up over the season. Check the top inch or two of mix often during California summer heat, since a pot dries faster than open ground. Water thoroughly until it drains through the holes, then empty whatever collects in the saucer. In cooler parts of the state, the tuber can be lifted and stored in a cool, dry spot over winter, much like a dahlia. In milder gardens, cut back frost-damaged top growth and let the pot dry out somewhat until new shoots appear in spring.

1 Your climate zone six WUCOLS zones, each from its own reference city
1.07gal per sq ft in JulyLow water use in the Central Valley zone
A year
6.84 gal per sq ft
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses
0.761.52.33.00.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.761.52.33.00.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

Four O'Clock: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.040.160.080.310.740.78
Feb0.050.260.080.350.930.93
Mar0.090.430.110.521.461.52
Apr0.120.610.140.641.891.95
May0.150.830.160.782.392.45
Jun0.160.990.170.922.852.79
Jul0.161.070.213.042.85
Aug0.150.950.190.932.792.6
Sep0.120.720.150.742.142.08
Oct0.090.470.110.531.461.49
Nov0.050.220.080.360.930.96
Dec0.030.140.070.270.650.68
Year1.26.841.557.3721.2721.08

How this is worked out: the WUCOLS water rating for each zone times that zone’s climate for the month. A dash means WUCOLS does not rate the plant there. The figures are what the plant uses, before sprinkler losses.

Plants with the same water needs 16

Rated low water in the Central Valley, like four o'clock. Plants that drink alike can share one valve and one schedule.

AgapanthusAgapanthus orientalislow water, Central Valley1.07 gal/sq ft in JulyGeraniumsPelargonium x hortorum and cvs.low water, Central Valley1.07 gal/sq ft in JulySalviaSalvia greggii ssp., cvs. & hybridslow water, Central Valley1.07 gal/sq ft in JulyIrisesIris germanicalow water, Central Valley1.07 gal/sq ft in JulySucculentsEcheveria spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyRussian SagePerovskia spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyYarrowAchillea millefolium (non-native hybrids)low water, Central Valley1.07 gal/sq ft in JulyMountain AlyssumAlyssum montanumlow water, Central Valley1.07 gal/sq ft in JulySilver SageSalvia argentealow water, Central Valley1.07 gal/sq ft in JulyPurple MulleinVerbascum phoeniceumlow water, Central Valley1.07 gal/sq ft in JulySilvery YarrowAchillea clavennaelow water, Central Valley1.07 gal/sq ft in JulyFern Leaf YarrowAchillea filipendulinalow water, Central Valley1.07 gal/sq ft in JulyCalifornia Native YarrowAchillea millefolium (CA native cultivars)low water, Central Valley1.07 gal/sq ft in JulyWoolly YarrowAchillea tomentosalow water, Central Valley1.07 gal/sq ft in JulyPerennial HollyhockAlcea rosea cvs.low water, Central Valley1.07 gal/sq ft in JulyMountain Lady's MantleAlchemilla alpinalow water, Central Valley1.07 gal/sq ft in July
Minutes for your sprinklers

Turn this into minutes on your water days

Every city page has a calculator that takes four o'clock, your sprinkler type and the month, and gives the minutes per water day for that supplier's schedule. Or put it in a zone of the personal watering plan and get all twelve months printed.

Questions people ask

How often should I water four o'clock in summer?

In July, established four o'clock in loam needs a deep watering about every 14 days in the Central Valley, about once a month or less on the south coast and about every 14 days in the South Inland zone. Sandy soil holds less water, so waterings come closer together. Clay stretches them. Check the soil before each watering and skip one after a soaking rain.

How much water does four o'clock need per day?

In July in the Central Valley, established four o'clock needs about 0.1 gallons a day for a plant 2 feet across and about 0.4 gallons a day for a plant 4 feet across. Give it in deep waterings spread days apart rather than a little every day, so the whole root zone gets wet.

Does watering for four o'clock change across California?

Yes. WUCOLS rates four o'clock separately for each of the six California climate zones: very low water in the North-Central Coastal zone, low water in the Central Valley zone, very low water in the South Coastal zone, low water in the South Inland zone, moderate water in the High and Intermediate Desert zone, moderate water in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

Why do my four o'clock flowers only open late in the day?

Four o'clock typically opens its flowers toward evening, with blooms closing by morning. Flowers can also open during very cloudy weather. Closed daytime flowers alone are not a reason to change irrigation.

Can four o'clock survive a dry summer without much care?

Established four o'clock has moderate drought tolerance, but still needs soil checks during dry weather. Use its local water rating when deciding whether to irrigate. Desert gardens carry moderate water ratings despite the lower coastal ratings.

Do I need to dig up four o'clock tubers for winter?

Where winters stay mild, the tuber can often overwinter in the ground with little attention. In colder parts of the state, lifting and storing the tuber in a cool, dry spot protects it from hard frost. Treat it much like a dahlia tuber in that case.

Why are four o'clock seedlings showing up all over my bed?

Four o'clock readily produces self-sown seedlings and can move beyond its original planting. Remove flowers before seed ripens and pull unwanted seedlings while small. Do not increase irrigation just to help an unwanted patch expand.

Is four o'clock considered weedy or invasive?

It can become weedy in warm climates where it self-sows without any control, forming more plants than many gardeners want. Removing spent flowers or unwanted seedlings keeps it in check. This tendency is separate from its moisture needs.

More plant watering guides

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Sources