WateringTimesWatering plan, $19
Tanacetum vulgare, WUCOLS IV

How often to water tansy in California

In July in the Central Valley, established tansy in loam needs a deep watering about every 5 days: about 1.5 gallons each time for a plant 2 feet across, about 1.9 gallons a week. Tansy is a tough, aromatic perennial with fern-like leaves and flat clusters of yellow button flowers on stems that can reach several feet. Established clumps tolerate dry soil, though they prefer moisture with good drainage. Both prolific seed production and spreading rhizomes can carry this plant beyond its original bed.

PerennialRated for 2 of 6 zones

How often to water tansy, 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 tansy 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 several inches down at the base of an older clump signals it needs a soak
  • Check soil moisture when leaves wilt or curl instead of deciding from their afternoon appearance alone
  • Inspect the root ball of a pale, sparse young plant before deciding whether it needs water
  • Softening stems above persistently wet soil call for a drainage check before another soak
  • Inspect leaning stems for damage and check soil conditions before adding water

How to water it

  • Soak the root zone at the base of the clump with drip or a slow hose rather than overhead watering
  • Let the top several inches of soil dry before watering an established plant again
  • Use well-drained soil and avoid low spots where water collects around the crown
  • Remove spent flower heads before they set seed if you want to limit where tansy spreads
  • Keep irrigation within the intended planting area and remove unwanted seedlings beyond it

Through the seasons

Check a young tansy closely while its root system establishes, then base watering on moisture beneath the clump. Mature plants tolerate dry soil but still have a moderate water rating in both evaluated regions. The leafy stems die back seasonally, and yellow flowers appear in summer and into fall. Keep plant material away from children and animals that might eat it. Coastal and valley winter rainfall can supply much of the cool-season need. WUCOLS rates tansy moderate water on the north-central coast and in the Central Valley. The south coast, South Inland, high desert and low desert have not been evaluated.

In pots

Watch a potted tansy for roots escaping through drainage holes, and remove spent blooms before seeds scatter beyond the container. Check the top inch or two of mix during California summer heat and water once it feels dry there. Let water run through the holes, then empty the saucer. Inspect nearby ground for seedlings instead of assuming the pot contains every route of spread. As leafy stems die back for winter, recheck the mix before watering again.

1 Your climate zone six WUCOLS zones, each from its own reference city
2.67gal per sq ft in JulyModerate water use in the Central Valley zone
A year
17.11 gal per sq ft
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses
0.671.32.02.70.4JAN0.65FEB1.09MAR1.52APR2.08MAY2.48JUN2.67JUL2.39AUG1.8SEP1.18OCT0.56NOV0.34DEC0.671.32.02.70.4JFM1.52AMJ2.67JAS1.18OND
Gallons per square foot per month, Central Valley. Peak 2.67 in Jul, 17.11 a year.

Monthly water need by climate zone

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

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.4––––
Feb0.530.65––––
Mar0.871.09––––
Apr1.181.52––––
May1.462.08––––
Jun1.612.48––––
Jul1.612.67––––
Aug1.492.39––––
Sep1.241.8––––
Oct0.871.18––––
Nov0.470.56––––
Dec0.310.34––––
Year1217.11––––

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 moderate water in the Central Valley, like tansy. Plants that drink alike can share one valve and one schedule.

DahliasDahlia spp.moderate water, Central Valley2.67 gal/sq ft in JulyFernsNephrolepis cordifolia (SHADE IN DESERT)moderate water, Central Valley2.67 gal/sq ft in JulyDayliliesHemerocallis spp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyBegoniasBegonia & ssp. & cvs. (shade in the desert)moderate water, Central Valley2.67 gal/sq ft in JulyCalla LiliesZantedeschia aethiopica SHADE IN DESERTmoderate water, Central Valley2.67 gal/sq ft in JulySageSalvia officinalis and cvs.moderate water, Central Valley2.67 gal/sq ft in JulyBicolor MonkshoodAconitum cammarummoderate water, Central Valley2.67 gal/sq ft in JulyGarden MonkshoodAconitum napellusmoderate water, Central Valley2.67 gal/sq ft in JulyCarpet BugleAjuga reptans (shade)moderate water, Central Valley2.67 gal/sq ft in JulySnowdrop WindflowerAnemone sylvestrismoderate water, Central Valley2.67 gal/sq ft in JulyMountain SandwortArenaria montanamoderate water, Central Valley2.67 gal/sq ft in JulySwamp MilkweedAsclepias incarnatamoderate water, Central Valley2.67 gal/sq ft in JulyOrange MilkweedAsclepias tuberosamoderate water, Central Valley2.67 gal/sq ft in JulyGreater MasterwortAstrantia majormoderate water, Central Valley2.67 gal/sq ft in JulyHardy BegoniaBegonia grandismoderate water, Central Valley2.67 gal/sq ft in JulyWax BegoniaBegonia semperflorensmoderate water, Central Valley2.67 gal/sq ft in July

Similar plants that need less water 16

Rated lower than tansy in the Central Valley. Worth a look for a new bed or a lawn replacement.

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 tansy, 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 much water does tansy need per day?

In July in the Central Valley, established tansy needs about 0.3 gallons a day for a plant 2 feet across and about 1.1 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 tansy change across California?

Yes. WUCOLS rates tansy separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, moderate water in the Central Valley zone, not evaluated in the South Coastal zone, not evaluated in the South Inland zone, not evaluated in the High and Intermediate Desert zone, not evaluated in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

Is tansy safe to grow around pets?

Keep tansy where pets cannot eat it. Its thujone can be poisonous if swallowed, and contact with the foliage can irritate skin. Wear gloves and cover your arms when handling it.

How do I stop tansy from spreading in my yard?

Remove fading flower heads before seed develops, and check surrounding ground for seedlings. Tansy also spreads through rhizomes and root fragments, so controlling seed alone will not contain an established patch. Keep inspecting its edges after removal work.

Why is my tansy flopping over?

Inspect the stems and growing conditions before assuming that extra water will help. Tansy grows in sun or partial shade and tolerates poor soil, but neither feature identifies the cause of flopping. Support damaged or leaning growth as needed while investigating the problem.

Can tansy survive a California summer without irrigation?

Tansy tolerates dry soil, but its California ratings are moderate water in the two evaluated regions. Check an established clump during prolonged dry weather rather than assuming its roots supply all it needs. Let the condition of the soil guide a soak.

Does tansy attract beneficial insects?

Its flowers provide food for pollinators. That value does not prevent tansy from spreading aggressively. On existing plants, remove spent heads before seed develops if you want to limit new seedlings.

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Sources