WateringTimesWatering plan, $19
Kerria japonica, WUCOLS IV

How often to water Japanese kerria in California

In July in the Central Valley, established Japanese kerria in loam needs a deep watering about every 8 days: about 8.8 gallons each time for a plant 4 feet across, about 7.6 gallons a week. Japanese kerria, also called Japanese rose, is a deciduous shrub of slender, arching green stems that forms a dense, twiggy mound. It grows up to about 7 feet tall and 9 feet wide. Bright yellow, rose-like flowers open in spring on the previous year's wood. It belongs in part shade, since full sun fades the flowers, and it wants loamy, well-drained soil.

ShrubRated for 4 of 6 zones

How often to water Japanese kerria, month by month

Your city
Plant width
4 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 Japanese kerria 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

  • When the ground under the arching canes feels dry a couple of inches down, kerria is ready for a soak
  • Leaves wilting and browning at the edges in a hot, dry spell can indicate thirst, especially in a sunny spot
  • Blackened twigs and spotted leaves after wet weather point to twig and leaf blight rather than a water shortage
  • Yellowing leaves over heavy, soggy clay can indicate root rot from poor drainage
  • Faded, washed-out flowers usually mean too much sun, not too little water

How to water it

  • Water across the root area under the arching stems with drip or a slow hose, keeping the foliage dry
  • Give each watering time to reach about a foot down, and wait until the upper inches dry out again
  • Plant in loamy, well-drained soil, steering clear of heavy clay and low wet spots
  • Skip heavy feeding, which makes this shrub weedy, and mulch lightly instead
  • Widen the watered area as suckers thicken the clump, and remove unwanted ones

Through the seasons

Keep a new kerria evenly moist through its first summer while roots spread. Established shrubs take deeper soakings with the surface allowed to dry between them. It flowers in spring on last year's stems, then drops its leaves in fall, leaving bright green twigs for winter. WUCOLS rates Japanese kerria moderate water on the north-central coast and in the Central Valley. South Inland and the high desert share that moderate water rating. WUCOLS has not evaluated it for the south coast or the low desert. Winter rain usually covers the bare shrub on the north-central coast and in the Central Valley.

In pots

Japanese kerria can grow in a large container in part shade, where its arching green stems spill over the rim. Choose loamy, free-draining potting soil and a container with open holes in the base. Through summer, push a finger into the soil every few days and water once the top 2 inches feel dry. Run water through until it drips out, and never leave the pot standing in its saucer. Prune flowered stems right after bloom to keep the plant in scale. After leaf fall, water lightly through winter.

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
0.761.52.33.00.4JAN0.65FEB1.09MAR1.52APR2.08MAY2.48JUN2.67JUL2.39AUG1.8SEP1.18OCT0.56NOV0.34DEC0.761.52.33.00.4JFM1.52AMJ2.67JAS1.18OND
Gallons per square foot per month, Central Valley. Peak 2.67 in Jul, 17.11 a year.

Monthly water need by climate zone

Japanese Kerria: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.4–0.780.74–
Feb0.530.65–0.870.93–
Mar0.871.09–1.31.46–
Apr1.181.52–1.611.89–
May1.462.08–1.952.39–
Jun1.612.48–2.292.85–
Jul1.612.67–2.513.04–
Aug1.492.39–2.332.79–
Sep1.241.8–1.862.14–
Oct0.871.18–1.331.46–
Nov0.470.56–0.90.93–
Dec0.310.34–0.680.65–
Year1217.11–18.4121.27–

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 Japanese kerria. Plants that drink alike can share one valve and one schedule.

RosesRosa hybrids..bushmoderate water, Central Valley2.67 gal/sq ft in JulyAzaleasRhododendron spp. (CA native and non-native spp.)moderate water, Central Valley2.67 gal/sq ft in JulyCamelliasCamellia japonica (SHADE IN DESERT)moderate water, Central Valley2.67 gal/sq ft in JulyGardeniasGardenia spp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyBird of ParadiseStrelitzia reginae (shade in desert)moderate water, Central Valley2.67 gal/sq ft in JulyHibiscusHibiscus rosa-sinensismoderate water, Central Valley2.67 gal/sq ft in JulySago PalmCycas revolutamoderate water, Central Valley2.67 gal/sq ft in JulyStar JasmineTrachelospermum jasminoides and cvs.moderate water, Central Valley2.67 gal/sq ft in JulyArborvitaeThuja occidentalis ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyBambooBambusa spp.moderate water, Central Valley2.67 gal/sq ft in JulyLilacsSyringa hybrids (including Descanso hybrids)moderate water, Central Valley2.67 gal/sq ft in JulySpireaSpiraea spp. (CA native and non native spp.)moderate water, Central Valley2.67 gal/sq ft in JulyButterfly BushBuddleja davidii and hybridsmoderate water, Central Valley2.67 gal/sq ft in JulySageSalvia officinalis and cvs.moderate water, Central Valley2.67 gal/sq ft in JulyRed BuckeyeAesculus paviamoderate water, Central Valley2.67 gal/sq ft in JulyWestern ServiceberryAmelanchier alnifoliamoderate water, Central Valley2.67 gal/sq ft in July

Similar plants that need less water 16

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

LavenderLavandula spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyRosemaryRosmarinus officinalislow water, Central Valley1.07 gal/sq ft in JulyBougainvilleaBougainvillea & spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyOlive TreesOlea europaea ssp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyCrape MyrtleLagerstroemia spp., hybrids & 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 JulyAloeAloe spp. & cvs.low 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 JulySagebrushArtemisia spp. (shrubby)low water, Central Valley1.07 gal/sq ft in JulyWild PrivetLigustrum vulgarelow water, Central Valley1.07 gal/sq ft in JulyCoralberrySymphoricarpos orbiculatus (SHADE)low water, Central Valley1.07 gal/sq ft in JulySydney Golden WattleAcacia longifolialow water, Central Valley1.07 gal/sq ft in JulyBlue Leaf WattleAcacia salignalow 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 Japanese kerria, 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 Japanese kerria in summer?

In July, established Japanese kerria in loam needs a deep watering about every 8 days in the Central Valley and about every 9 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 Japanese kerria need per day?

In July in the Central Valley, established Japanese kerria needs about 1.1 gallons a day for a plant 4 feet across and about 4.3 gallons a day for a plant 8 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 Japanese kerria change across California?

Yes. WUCOLS rates Japanese kerria 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, moderate water in the South Inland zone, moderate water 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.

Why are my kerria flowers fading?

Full sun bleaches the yellow flowers quickly. Kerria does best in part or dappled shade, where blooms hold their color longer. Shading the plant helps more than extra water.

When should I prune Japanese kerria?

Prune right after flowering, since it blooms on the previous year's wood. Remove old or leggy canes at the base, or cut the whole plant to the ground to renew it. Water well as new canes grow.

Why do kerria stems stay green in winter?

Its slender stems are naturally green, shiny and zigzag, which adds color after the leaves drop. That color is not a sign of a watering problem.

Can you overwater Japanese kerria?

Yes. It wants well-drained soil, and heavy, wet clay can lead to root rot. Let the upper soil dry between soakings, and keep water off the leaves in wet weather to limit blight.

Does kerria spread?

It sends up suckers that thicken the clump, and they should be removed where unwanted. High fertilization makes it weedier. Feed lightly and keep the suckers in check.

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Sources