WateringTimesWatering plan, $19
Acorus calamus 'Variegatus', WUCOLS IV

How often to water variegated sweet flag in California

In July in the Central Valley, established variegated sweet flag in loam needs a deep watering about every 3 days: about 1.5 gallons each time for a plant 2 feet across, about 3.0 gallons a week. Variegated sweet flag is an iris-like perennial with cream and green striped leaves that rise from thick spreading rhizomes. It is a marginal water plant suited to pond edges, bog gardens and consistently soggy beds. Unlike most garden perennials, letting its soil dry out works against it rather than toughening the roots.

PerennialRated for 4 of 6 zones

How often to water variegated sweet flag, 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 variegated sweet flag 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 pulling away from the rhizomes and drying at the surface signals sweet flag needs water right away
  • Leaf tips browning and curling in a bed that is allowed to dry between soakings can indicate the plant is too dry for its needs
  • Water more than nine inches above the planted rhizomes exceeds the shallow standing water recommended for this sweet flag
  • Sparse new growth in a bed that has been allowed to dry out repeatedly can signal chronic underwatering

How to water it

  • Plant variegated sweet flag directly in pond margins, bog beds or containers standing in a saucer of water
  • Keep the soil saturated at the root zone rather than allowing the surface to dry between waterings
  • Use rich, organic soil that holds moisture, mounding it if the bed is not naturally boggy
  • Limit standing water over the crown to a few inches so the rhizomes stay covered but not deeply submerged
  • Extend the wet zone outward as the clump's rhizomes spread

Through the seasons

A newly planted variegated sweet flag needs its bed or pot kept wet while the rhizomes establish, with little room for the soil to dry. Established clumps die back in winter and send up fresh striped leaves from thick rhizomes each spring. Watering matters through the entire growing season from spring into fall, since this plant does not adopt a drought tolerant summer pattern. Winter rain rarely covers its needs on its own, since a pond edge or bog bed depends on a steady water source beyond seasonal storms. WUCOLS rates variegated sweet flag high water on the north-central coast, in the Central Valley, on the south coast and in South Inland. WUCOLS marks it as not suited to the high desert or the low desert.

In pots

Grow variegated sweet flag in a pot set inside a larger saucer or basin so water always stands at its base. Check the saucer during California summer heat and refill it before it runs dry, since this plant does not tolerate drying out like a typical container plant. Use a rich, moisture retentive mix rather than a fast-draining one. Divide a crowded pot every few years as the rhizomes fill it. In winter, keep the mix damp but reduce standing water if the pot sits in a cold spot.

1 Your climate zone six WUCOLS zones, each from its own reference city
4.27gal per sq ft in JulyHigh water use in the Central Valley zone
A year
27.38 gal per sq ft
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses
1.12.13.24.30.64JAN1.04FEB1.74MAR2.43APR3.32MAY3.97JUN4.27JUL3.82AUG2.88SEP1.88OCT0.89NOV0.55DEC1.12.13.24.30.64JFM2.43AMJ4.27JAS1.88OND
Gallons per square foot per month, Central Valley. Peak 4.27 in Jul, 27.38 a year.

Monthly water need by climate zone

Variegated Sweet Flag: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.60.641.241.24––
Feb0.841.041.291.39––
Mar1.391.741.842.08––
Apr1.882.432.232.58––
May2.333.322.583.12––
Jun2.583.972.783.67––
Jul2.584.273.174.02––
Aug2.383.822.983.72––
Sep1.982.882.382.98––
Oct1.391.881.842.13––
Nov0.740.891.341.44––
Dec0.50.551.041.09––
Year19.227.3824.829.46––

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 high water in the Central Valley, like variegated sweet flag. Plants that drink alike can share one valve and one schedule.

Japanese Sweet FlagAcorus gramineushigh water, Central Valley4.27 gal/sq ft in JulyRed GingerAlpinia purpuratahigh water, Central Valley4.27 gal/sq ft in JulyShell GingerAlpinia zerumbethigh water, Central Valley4.27 gal/sq ft in JulySiberian BuglossBrunnera macrophyllahigh water, Central Valley4.27 gal/sq ft in JulyMarsh MarigoldCaltha palustrishigh water, Central Valley4.27 gal/sq ft in JulyUmbrella Sedge and PapyrusCyperus spp. (CA native and non-native species)high water, Central Valley4.27 gal/sq ft in JulyUmbrella PlantDarmera peltata (Peltiphyllum)high water, Central Valley4.27 gal/sq ft in JulyFoxgloveDigitalis purpurea cvshigh water, Central Valley4.27 gal/sq ft in JulyLeopard PlantFarfugium japonicum cvs. (Ligularia tussilaginea cvs.)high water, Central Valley4.27 gal/sq ft in JulyTransvaal DaisyGerbera jamesonii & hybridshigh water, Central Valley4.27 gal/sq ft in JulyGiant GunneraGunnera manicatahigh water, Central Valley4.27 gal/sq ft in JulyWhite Ginger LilyHedychium coronariumhigh water, Central Valley4.27 gal/sq ft in JulyJapanese IrisIris ensatahigh water, Central Valley4.27 gal/sq ft in JulyRushJuncus aquatic spp. (native and non-native spp.)high water, Central Valley4.27 gal/sq ft in JulyCardinal FlowerLobelia cardinalis hybrids and cvs. (CA native and non-native spp.)high water, Central Valley4.27 gal/sq ft in JulyBananaMusa spp. (shade in low desert)high water, Central Valley4.27 gal/sq ft in July

Similar plants that need less water 16

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

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
Minutes for your sprinklers

Turn this into minutes on your water days

Every city page has a calculator that takes variegated sweet flag, 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 variegated sweet flag in summer?

In July, established variegated sweet flag in loam needs a deep watering about every 3 days in the Central Valley, about every 5 days on the south coast and about every 4 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 variegated sweet flag need per day?

In July in the Central Valley, established variegated sweet flag needs about 0.4 gallons a day for a plant 2 feet across and about 1.7 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 variegated sweet flag change across California?

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

Can I grow variegated sweet flag without a pond?

Yes, as long as the container or bed can hold standing water or stay constantly saturated. A saucer kept full beneath a pot works well for this purpose. Without a steady water source, the leaves will scorch and thin quickly.

Why are the leaves on my sweet flag losing their stripes?

Cream to yellow stripes are characteristic of this cultivar. It grows in full sun or partial shade, so faded stripes alone do not establish a watering or light problem.

How deep can I plant sweet flag in a pond?

Set it at the pond edge or on a shallow shelf, with the rhizomes just below the soil surface. It does well in standing water up to about nine inches deep. A container set in shallow water also works.

Is variegated sweet flag hard to contain near a pond?

It spreads by rhizomes into a slowly widening clump rather than the fast spread reported for the plain species. Dividing it every few years keeps a bed or pond edge in bounds. Keep an eye on the clump size near natural waterways.

Can sweet flag survive being allowed to dry out occasionally?

It has little tolerance for repeated drying, unlike many garden perennials. A dried-out bed can scorch and thin the leaves within days. Keep the root zone consistently wet rather than treating this like a typical perennial.

Does variegated sweet flag need full sun?

It grows well in full sun near the coast and appreciates afternoon shade in hot inland spots. More shade can mean the soil stays wet longer between checks. Either way, the root zone should not be allowed to dry out.

More plant watering guides

Japanese Sweet FlagWhite AlderRed AlderRed GingerShell GingerBog RosemaryRiver BirchWater Birch

Sources