WateringTimesWatering plan, $19
Verbena bonariensis ssp. & cvs., WUCOLS IV

How often to water verbena bonariensis in California

In July in the Central Valley, established verbena bonariensis 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. Verbena bonariensis, also called tall verbena, sends up tall, wiry stems topped with small rounded clusters of purple flowers. Its toothed leaves stay mostly near the base. It blooms from spring or summer into fall and draws butterflies, bees and hummingbirds. It self-sows freely and can be invasive in California, especially in moist soil.

PerennialRated for 6 of 6 zones

How often to water verbena bonariensis, 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 verbena bonariensis 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 3 inches down near the base of the clump means verbena bonariensis can take a drink
  • Flower clusters fading early and stems drooping in summer heat can show the roots have dried
  • A white powdery coating on the leaves points to powdery mildew, not thirst
  • Seedlings popping up in watered beds nearby show how readily it spreads in moist soil
  • Yellowing at the base and soft stems in soggy ground point to poor drainage

How to water it

  • Water verbena bonariensis at the base of the clump rather than over the tall stems
  • Soak the soil 6 to 8 inches deep, then let it dry well before the next watering
  • Plant in full sun in average to lean soil that drains, from sand to clay
  • Skip mulch that keeps the soil damp, since moist ground favors its seedlings
  • Keep irrigation to the clump itself so seedlings have less moist ground to take hold

Through the seasons

Water new plants regularly until they settle, then let the soil dry well between soakings. Established clumps handle dry spells in mild coastal and valley gardens, while hot inland gardens call for steadier checks. Flowers run from spring or summer into fall. It is a tender perennial that may act as an annual after a cold winter, and its seedlings return on their own. In WUCOLS, verbena bonariensis is low water in the Central Valley, on the south coast and on the north-central coast. South Inland, the high desert and the low desert carry a moderate water rating.

In pots

Verbena bonariensis grows well in a deep pot, which also limits its self-sowing in garden beds. Use a container with drainage holes and an average, free-draining mix. During hot weather, test the mix with a finger every few days and water once the top 2 inches are dry. Let the water run through and empty the saucer. Leave a few dead stems standing over winter if you like, since native bees can nest in the hollow stalks.

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

Verbena Bonariensis: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.150.160.310.780.740.78
Feb0.210.260.320.870.930.93
Mar0.350.430.461.31.461.52
Apr0.470.610.561.611.891.95
May0.580.830.641.952.392.45
Jun0.640.990.692.292.852.79
Jul0.641.070.792.513.042.85
Aug0.60.950.742.332.792.6
Sep0.50.720.61.862.142.08
Oct0.350.470.461.331.461.49
Nov0.190.220.330.90.930.96
Dec0.120.140.260.680.650.68
Year4.86.846.218.4121.2721.08

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 verbena bonariensis. 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 verbena bonariensis, 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 verbena bonariensis in summer?

In July, established verbena bonariensis in loam needs a deep watering about every 14 days in the Central Valley, about every 18 days on the south coast and about every 6 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 verbena bonariensis need per day?

In July in the Central Valley, established verbena bonariensis 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 verbena bonariensis change across California?

Yes. WUCOLS rates verbena bonariensis separately for each of the six California climate zones: low water in the North-Central Coastal zone, low water in the Central Valley zone, low water in the South Coastal zone, moderate 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.

Is verbena bonariensis invasive in California?

It self-sows freely and carries a high risk of invasiveness in California, especially in moist soil. Cut flower heads before they drop seed, and pull seedlings while small.

Does verbena bonariensis attract butterflies?

Yes. Its purple clusters draw butterflies, bees and hummingbirds, and goldfinches eat the seeds. Water at the base so you do not knock pollinators off the flowers.

Should I cut back verbena bonariensis?

You can leave some hollow stems standing, since native bees nest in them. Cutting seed heads early limits self-sowing. Either way, watering stays the same.

Why are my verbena leaves white?

A white, powdery film is powdery mildew. Give plants room for air to move, and water the soil rather than the leaves.

Can you overwater verbena bonariensis?

Yes. It prefers average to dry soil with good drainage, and extra water mainly feeds its seedlings. Let the soil dry well between soakings.

More plant watering guides

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Sources