WateringTimesWatering plan, $19
Betula occidentalis, WUCOLS IV

How often to water water birch in California

In July in the Central Valley, established water birch in loam needs a deep watering about every 5 days: about 55 gallons each time under a 10 foot canopy, about 76 gallons a week. Water birch is a western native that grows in clumps along mountain streams and springs, as a multi-stemmed shrub or a tree. Its shiny, reddish-brown bark does not peel, and its leaves can color brightly in fall. It is a thirsty tree that does best in soil kept moist through the dry season.

TreeCalifornia nativeRated for 4 of 6 zones

How often to water water birch, month by month

Your city
Canopy width
10 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 water birch 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 under the branches, 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 canopy width

A tree with its canopy width marked across the widest branches and the circle under it shaded blue

Measure across the branches, from the tips of the outer leaves on one side to the tips on the other. A tape works, or pace it out.

Water the whole circle under the branches, shown in blue. The gallons here cover that circle.

A wider canopy means more gallons each watering, not more waterings. While the tree is young, measure again each spring.

How to tell it needs water

  • Soil dry 3 to 4 inches down around the stems means a water birch is overdue for a deep soak
  • Leaves that wilt or brown at the edges in summer heat point to a dry root zone
  • Foliage that turns pale green, then yellow, then brown, with D-shaped holes in the bark, points to bronze birch borer in a stressed tree
  • Yellow leaves with green veins in alkaline soil point to iron chlorosis rather than thirst
  • Aphids or leaf miners on the foliage are common birch pests, not a sign that the watering is off

How to water it

  • Lay soaker hoses or drip line across the whole root zone to keep the roots cool and moist
  • Spread a thick layer of bark mulch over the roots, kept a few inches back from the stems
  • Soak until water reaches about 18 inches down, and water again before the top few inches dry out
  • Plant on the east side of a building or in a naturally damp low spot, not against a hot south or west wall
  • Widen the watered area as the clump spreads and new stems rise from the base

Through the seasons

Keep a new water birch moist through its first few summers while its roots spread. Established trees still need regular deep watering, since birch need more water than most other trees. Catkins appear in spring and small cones follow in late summer. Leaves can color brightly in fall before they drop. The bare tree rests through winter, when rain covers the cool months on the coast and in the valley. In hot, dry interior areas birch tend to live only a short time. WUCOLS rates it 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

Water birch grows into a large clump or tree, so a container suits it only while young. Use a big pot with open drainage holes and a mix that holds moisture. Check the mix 1 to 2 inches down daily in summer, since this thirsty tree dries a pot quickly. Water until it drains from the holes. Keep the pot out of hot afternoon sun and off hot paving. In winter the leafless tree uses far less water, so check the mix before each watering.

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

Water Birch: 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 water birch. Plants that drink alike can share one valve and one schedule.

Big Leaf MapleAcer macrophyllumhigh water, Central Valley4.27 gal/sq ft in JulyWhite AlderAlnus rhombifoliahigh water, Central Valley4.27 gal/sq ft in JulyRed AlderAlnus rubra (Alnus oregona)high water, Central Valley4.27 gal/sq ft in JulyRiver BirchBetula nigrahigh water, Central Valley4.27 gal/sq ft in JulyEuropean White BirchBetula pendulahigh water, Central Valley4.27 gal/sq ft in JulyWhite-Barked Himalayan BirchBetula utilis var. jacquemontiihigh water, Central Valley4.27 gal/sq ft in JulyEuropean BeechFagus sylvaticahigh water, Central Valley4.27 gal/sq ft in JulyBlack CottonwoodPopulus trichocarpa (Populus balsamifera)high water, Central Valley4.27 gal/sq ft in JulyCarolina PoplarPopulus x canadensishigh water, Central Valley4.27 gal/sq ft in JulyWeeping WillowSalix babylonicahigh water, Central Valley4.27 gal/sq ft in JulyPeking WillowSalix matsudanahigh water, Central Valley4.27 gal/sq ft in JulyCoast RedwoodSequoia sempervirenshigh water, Central Valley4.27 gal/sq ft in JulyVine MapleAcer circinatumhigh water, Central Valley4.27 gal/sq ft in JulyHydrangeaHydrangea macrophylla & cvs.high water, Central Valley4.27 gal/sq ft in JulyBlueberriesVaccinium hybrids and cvs (CA native and non- native spp.)high water, Central Valley4.27 gal/sq ft in JulyShell GingerAlpinia zerumbethigh water, Central Valley4.27 gal/sq ft in July

Similar plants that need less water 16

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

Citrus TreesCitrus spp.moderate water, Central Valley2.67 gal/sq ft in JulyJapanese MapleAcer palmatummoderate water, Central Valley2.67 gal/sq ft in JulyAvocado TreesPersea americanamoderate water, Central Valley2.67 gal/sq ft in JulyMagnolia TreesMagnolia grandiflora ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyPalm TreesSyagrus romanzoffiana (Arecastrum romanzoffianum)moderate water, Central Valley2.67 gal/sq ft in JulyApple TreesMalus spp. (edible) e.g, 'Anna' (low chill variety for low desert)moderate water, Central Valley2.67 gal/sq ft in JulyPeach TreesPrunus spp. ediblemoderate water, Central Valley2.67 gal/sq ft in JulyPersimmon TreesDiospyros kakimoderate water, Central Valley2.67 gal/sq ft in JulyAmur MapleAcer ginnalamoderate water, Central Valley2.67 gal/sq ft in JulyFernleaf MapleAcer japonicummoderate water, Central Valley2.67 gal/sq ft in JulyBox ElderAcer negundomoderate water, Central Valley2.67 gal/sq ft in JulyNorway MapleAcer platanoidesmoderate water, Central Valley2.67 gal/sq ft in JulyRed MapleAcer rubrummoderate water, Central Valley2.67 gal/sq ft in JulyChinese MapleAcer truncatummoderate water, Central Valley2.67 gal/sq ft in JulyRed BuckeyeAesculus paviamoderate water, Central Valley2.67 gal/sq ft in JulyRed HorsechestnutAesculus x carneamoderate 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 water birch, 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 water birch in summer?

In July, established water birch in loam needs a deep watering about every 5 days in the Central Valley, about every 7 days on the south coast and about every 5 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 water birch need per day?

In July in the Central Valley, established water birch needs about 11 gallons a day under a 10 foot canopy and about 43 gallons a day under a 20 foot canopy. Give it in deep waterings spread days apart rather than a little every day, so the whole root zone gets wet.

Does watering for water birch change across California?

Yes. WUCOLS rates water birch 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.

How do I protect water birch from borers?

Keep the tree well watered and mulched, since bronze birch borer goes after stressed birch. Avoid hot spots such as the south and west sides of buildings. Do not fertilize unless a deficiency is confirmed, because feeding raises the tree's water demand.

When should I prune water birch?

Prune in the dormant season, from late fall through March, when borer adults are not flying. Avoid spring pruning, since cuts bleed while the sap is running. Little pruning is needed beyond removing dead wood.

Can water birch grow in a wet spot?

It grows naturally along streams and springs. In gardens it suits small groups in consistently moist soil along ponds and in low spots. Make sure the spot stays damp through summer, not only in winter.

Will water birch grow near the coast?

Yes. It is a mountain native, yet it grows well in coastal gardens. It still needs regular summer water there.

Why is my birch declining in the Central Valley?

Birch typically have a short life in hot, dry interior parts of California. Heat stress also opens the door to bronze birch borer. Deep, regular watering, mulch and a cooler east-facing spot give it the best chance.

How big does water birch get?

Most often it grows as a multi-stemmed shrub 10 to 15 feet tall. On good sites it can become a multi-trunked tree to 40 feet or more.

More plant watering guides

Red-veined EnkianthusAbyssinian BananaEuropean BeechLeopard PlantTransvaal DaisyGiant GunneraWhite Ginger LilyClimbing Hydrangea

Sources