WateringTimesWatering plan, $19
Achillea millefolium 'Sonoma Coast', WUCOLS IV

How often to water Sonoma Coast yarrow in California

In July in the Central Valley, established Sonoma Coast yarrow 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. Sonoma Coast yarrow is a low, spreading selection of the native common yarrow, collected on the Sonoma County coast. The mat stays about a foot tall and up to 3 feet wide, with deep green, ferny foliage. Particularly dense heads of white flowers attract butterflies and beneficial insects. It takes clay, sun or part shade, and only occasional water.

PerennialRated for 5 of 6 zones

How often to water Sonoma Coast 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 Sonoma Coast 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 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 under the mat in a dry summer signals Sonoma Coast yarrow can take a soak
  • Deep green leaves fading to gray green and drooping can indicate a long dry spell
  • Flower heads browning early can follow drought during bloom
  • Mushy, browning patches in soggy, compacted clay point to too much water

How to water it

  • Water the whole mat with a soaker or low spray rather than a single point
  • Soak a few inches down, then let the soil dry before watering again
  • Plant in sun or part shade, in clay or lighter soil that does not stay waterlogged
  • Let it creep between stepping stones or fill a meadow planting
  • Shear spent flower heads to tidy the mat

Through the seasons

Keep new plants moist until they begin to spread, then shift to occasional soaks. Once settled, the mat handles dry spells and needs little summer irrigation. It suits meadows and the gaps between stone paths, and shearing spent heads keeps it neat. Winter rain normally covers its needs away from the deserts. On the north-central coast, WUCOLS rates Sonoma Coast yarrow low water. The Central Valley, the south coast, South Inland and the low desert also carry a low water rating. WUCOLS has not evaluated it for the high desert.

In pots

Sonoma Coast yarrow makes a soft, low filler in a wide container or a planter edge. Water once the top two inches of mix are dry, then let the water run out completely. Summer sun can dry a shallow pot within a few days. Keep the saucer empty. Trim faded flower heads to keep it neat. In winter, rain usually covers it, so hold off unless the mix is dry.

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
0.280.570.851.10.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.280.570.851.10.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

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

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.150.160.310.31–0.31
Feb0.210.260.320.35–0.37
Mar0.350.430.460.52–0.61
Apr0.470.610.560.64–0.78
May0.580.830.640.78–0.98
Jun0.640.990.690.92–1.12
Jul0.641.070.791–1.14
Aug0.60.950.740.93–1.04
Sep0.50.720.60.74–0.83
Oct0.350.470.460.53–0.6
Nov0.190.220.330.36–0.38
Dec0.120.140.260.27–0.27
Year4.86.846.27.37–8.43

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 Sonoma Coast yarrow. 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 Sonoma Coast 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 Sonoma Coast yarrow in summer?

In July, established Sonoma Coast yarrow 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 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 Sonoma Coast yarrow need per day?

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

Yes. WUCOLS rates Sonoma Coast 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, not evaluated 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.

What makes Sonoma Coast yarrow different?

It was selected on the Sonoma County coast for its deep green foliage and especially dense white flower heads. It stays low, about a foot tall. It spreads into a mat up to about 3 feet wide.

Can Sonoma Coast yarrow grow in clay?

Yes, it handles clay soil. Avoid spots where water stands after rain. Water less often in clay than in sand.

Can I plant Sonoma Coast yarrow between pavers?

Yes, its low foliage creeps nicely between stone paths. The stones keep the soil cool. Check the soil in the joints before watering.

Does Sonoma Coast yarrow attract butterflies?

Yes, its white flowers draw many butterflies and beneficial insects. It is a good meadow plant. Avoid spraying pesticides near it.

Does Sonoma Coast yarrow need full sun?

It grows in sun or part shade. Shade also keeps soil moist longer.

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Sources