WateringTimesWatering plan, $19
Betula nigra, WUCOLS IV

How often to water river birch in California

In July in the Central Valley, established river 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. River birch is a fast-growing deciduous tree native to riverbanks and floodplains of the eastern United States, often grown with several trunks. Its cinnamon-brown bark peels in papery curls to show salmon and tan layers, and its leaves turn yellow in fall. It is perhaps the most heat-tolerant birch, but it wants consistently moist soil and rates high water wherever WUCOLS lists it.

TreeRated for 4 of 6 zones

How often to water river 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 river 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

  • Inner leaves yellowing and dropping in summer mean the soil has run dry, a classic river birch stress signal
  • Soil dry 2 inches down under the canopy in summer means it is time for a long soak, since it wants steady moisture
  • Roots matting at the surface under frequent light sprinkling show the watering is too shallow, not too scarce
  • Scattered dieback on an older tree in a hot, dry inland garden can signal the decline birches suffer in hot summers
  • Twigs littering the ground are normal shedding for this tree, not a sign of thirst

How to water it

  • Lay soaker hoses under the canopy and run them long enough to wet the soil about 18 inches deep
  • Keep the soil consistently moist through the dry season rather than letting it dry out between soakings
  • Spread bark mulch over the root zone to keep the soil cool and damp
  • Plant in full sun to part shade in moist, slightly acid soil, away from the house and its gutters
  • Expand the soaker rings outward as the canopy spreads

Through the seasons

Keep a new tree evenly moist through its first summers. River birch needs steady water all through the dry season, and it sheds inner leaves if the soil dries. Leaves turn yellow and drop early in fall, and the peeling bark stands out in winter. In hot, dry inland areas birches often decline within about 20 years, so deep, regular watering matters most there. WUCOLS rates river birch 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

River birch grows into a large, fast tree, so a container works only for a young plant before it goes in the ground. Use a deep pot with drainage holes and a moisture-holding mix. In hot weather, check the mix daily and water before the top inch dries, since dry roots make it shed leaves. Let water drain through, then empty the saucer. Plant it out within a season or two.

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

River 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 river 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 JulyWater BirchBetula occidentalishigh 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 river 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 river 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 river birch in summer?

In July, established river 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 river birch need per day?

In July in the Central Valley, established river 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 river birch change across California?

Yes. WUCOLS rates river 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.

Why is my river birch dropping leaves in summer?

River birch sheds interior leaves during droughts and dry periods. It is a sign the soil has dried out. Soak the root zone deeply and keep it consistently moist.

Can river birch grow in wet soil?

Yes. It grows wild along riverbanks and floodplains and tolerates flooding for long periods. It suits rain gardens and low, damp spots.

Why is the bark peeling on my river birch?

Peeling is natural and is one of its best features. Thin, papery layers curl back to show cinnamon, salmon and brown shades, especially on older trunks.

Does river birch get bronze birch borer?

It is resistant to the bronze birch borer that kills many other birches. Aphids and leaf miners may still appear, and leaf spot can show up in damp weather.

How long does river birch live in California?

Birches tend to be short-lived where summers are hot and dry, often declining within about 20 years. Deep, steady watering and mulch give a river birch its best chance.

Is river birch messy?

It drops a lot of twigs, so it suits less manicured areas. Keep it away from the house, where falling branchlets clog gutters.

More plant watering guides

FoxgloveRed-veined EnkianthusAbyssinian BananaEuropean BeechLeopard PlantTransvaal DaisyGiant GunneraWhite Ginger Lily

Sources