WateringTimesWatering plan, $19
Achillea millefolium (non-native hybrids), WUCOLS IV

How often to water yarrow in California

In July in the Central Valley, established yarrow in loam needs a deep watering about every 20 days: about 2.2 gallons each time for a plant 2 feet across, about 0.8 gallons a week. Garden yarrow forms a low mat of ferny leaves beneath flat flower heads. Spreading rhizomes let a clump widen beyond its original planting spot. Established plants need little water, while rich soil and frequent irrigation can encourage soft stems that fall outward.

Ground coverPerennialRated for 6 of 6 zones

How often to water yarrow, 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 yarrow 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 1.5 feet 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 2 to 3 inches down beside a yarrow clump signals that its root area needs a moisture check
  • Crisp lower leaves and early fading flower heads can accompany dryness but do not establish the cause alone
  • Ferny foliage still limp in the morning can indicate thirst when the soil is dry
  • Flopping flower stems can reflect excess water, rich soil or shade rather than thirst

How to water it

  • Water around the yarrow clump with drip or a slow hose beneath the ferny foliage
  • Soak the top foot of soil and let the upper root area dry before another application
  • Use a slight mound in heavy clay so the yarrow crown does not remain waterlogged
  • Keep mulch thin and clear of the crown and emerging rhizomes
  • Move emitters toward the spreading clump edges instead of leaving water only at the old center

Through the seasons

Keep a new yarrow root ball lightly moist through its first summer while rhizomes extend into nearby soil. Established clumps can take deeper, more widely spaced soakings. Growth slows in cold weather, leaving a low rosette of ferny leaves. Irrigation matters mainly from late spring through early fall as flower heads form and open. Coastal and Central Valley winter rain can supply moisture; check both deserts during long dry winter spells. WUCOLS rates yarrow low water in all six climate zones.

In pots

Yarrow spreads sideways by rhizomes, so use a roomy container with freely draining mix. Check the top inch or two often in California summer heat and water when dry. Soak until excess leaves the drainage holes, then empty the saucer so the crown does not remain over trapped water. Divide the clump when rhizomes crowd the pot. Winter growth slows, so check whether rain has moistened the mix before watering during a dry spell.

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
0.300.610.921.20.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.300.610.921.20.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

Yarrow: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.150.160.310.310.30.31
Feb0.210.260.320.350.370.37
Mar0.350.430.460.520.580.61
Apr0.470.610.560.640.760.78
May0.580.830.640.780.950.98
Jun0.640.990.690.921.141.12
Jul0.641.070.7911.221.14
Aug0.60.950.740.931.121.04
Sep0.50.720.60.740.860.83
Oct0.350.470.460.530.580.6
Nov0.190.220.330.360.370.38
Dec0.120.140.260.270.260.27
Year4.86.846.27.378.518.43

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 yarrow. Plants that drink alike can share one valve and one schedule.

BougainvilleaBougainvillea & spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyAgapanthusAgapanthus orientalislow water, Central Valley1.07 gal/sq ft in JulyGeraniumsPelargonium x hortorum and cvs.low water, Central Valley1.07 gal/sq ft in JulyLantanaLantana camara ssp. & 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 JulyJunipersJuniperus spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyRussian SagePerovskia spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyMountain AlyssumAlyssum montanumlow water, Central Valley1.07 gal/sq ft in JulySagebrushArtemisia spp. (shrubby)low 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 July
Minutes for your sprinklers

Turn this into minutes on your water days

Every city page has a calculator that takes yarrow, 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 yarrow in summer?

In July, established yarrow in loam needs a deep watering about every 20 days in the Central Valley, about every 27 days on the south coast and about every 22 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 yarrow need per day?

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

Yes. WUCOLS rates yarrow 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, low water in the South Inland zone, low water in the High and Intermediate Desert zone, low water in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

How do I water newly planted yarrow?

Soak the nursery root ball at planting, then check its upper inch or two during warm weather. The small ball can dry sooner than the surrounding bed. Widen coverage as new growth spreads beyond it.

How do I water yarrow seeds?

Keep the top half inch of the seedbed damp while the tiny seeds germinate. A fine spray helps avoid washing them away. Once seedlings have true leaves, gradually water more deeply and allow slight surface drying.

Why is my yarrow flopping?

Check for shade, rich soil and frequent irrigation before assuming thirst. Soft stems may struggle to hold the flat flower heads. Cut spent stems back and adjust watering according to the soil rather than the leaning flowers alone.

Does yarrow need extra fertilizer for stronger stems?

Do not feed yarrow solely to correct leaning stems. If growth remains weak in full sun with suitable moisture, test the soil before feeding.

When should I divide a potted yarrow?

Divide potted yarrow in early spring as new growth begins. Keep vigorous outer sections with roots and discard dead material from the center.

More plant watering guides

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Sources