WateringTimesWatering plan, $19
Alnus rhombifolia, WUCOLS IV

How often to water white alder in California

In July in the Central Valley, established white alder 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. White alder is a fast-growing deciduous native tree of moist West Coast canyons, found where water flows year-round. Young trees shoot up quickly before slowing on the way to about 50 feet. It fixes its own nitrogen, casts dense, cool shade, and will even grow in a creek bed with water running around its roots.

TreeCalifornia nativeRated for 5 of 6 zones

How often to water white alder, 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 white alder 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 drying at the surface under the canopy in summer means white alder needs water now
  • Leaves yellowing and dropping in midsummer point to drought stress
  • Leaf edges browning in a hot, dry spell suggest the roots are too dry
  • Few plants thriving beneath the tree is normal, since its shade and roots compete hard

How to water it

  • Keep the root zone moist all year with deep, frequent watering
  • Plant it beside a creek, pond or wet spot where other trees drown
  • Give it full sun and room to grow fast
  • Open up the limbs if you want to garden beneath it
  • Do not plant it in a dry garden

Through the seasons

Water a young tree heavily and often as it races upward. Established trees still need constant moisture, since white alder is not drought tolerant and grows wild only where water lasts all year. Leaves drop in fall, and it fixes its own nitrogen, so it needs little feeding. White alder carries a high water rating from WUCOLS on the north-central coast and the south coast, in the Central Valley and South Inland, and in the high desert. The low desert is the one zone WUCOLS marks it as not suited to.

In pots

White alder grows too fast and thirsty for a pot beyond its first year, so treat a container as a short stop. A young tree can wait in a deep tub of moisture-holding mix stood in a tray of water. Add water whenever the surface begins to dry, which may be every day in summer. Never let the mix dry out. Move it into a wet, sunny spot in the ground early.

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
1.22.43.64.90.64JAN1.04FEB1.74MAR2.43APR3.32MAY3.97JUN4.27JUL3.82AUG2.88SEP1.88OCT0.89NOV0.55DEC1.22.43.64.90.64JFM2.43AMJ4.27JAS1.88OND
Gallons per square foot per month, Central Valley. Peak 4.27 in Jul, 27.38 a year.

Monthly water need by climate zone

White Alder: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.60.641.241.241.19–
Feb0.841.041.291.391.49–
Mar1.391.741.842.082.33–
Apr1.882.432.232.583.03–
May2.333.322.583.123.82–
Jun2.583.972.783.674.56–
Jul2.584.273.174.024.86–
Aug2.383.822.983.724.46–
Sep1.982.882.382.983.42–
Oct1.391.881.842.132.33–
Nov0.740.891.341.441.49–
Dec0.50.551.041.091.04–
Year19.227.3824.829.4634.03–

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 white alder. Plants that drink alike can share one valve and one schedule.

Big Leaf MapleAcer macrophyllumhigh 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 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 white alder 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 white alder, 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 white alder in summer?

In July, established white alder 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 white alder need per day?

In July in the Central Valley, established white alder 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 white alder change across California?

Yes. WUCOLS rates white alder 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, high water 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.

Is white alder drought tolerant?

No, it is not drought tolerant. It grows wild where water flows year-round. Keep its roots moist.

How fast does white alder grow?

Very fast, to about 30 feet in five or six years. Then growth slows toward 50 feet. Give it room.

Can I grow plants under white alder?

Its shade is dense and its roots compete hard, so few plants thrive beneath it. Opening up the limbs helps a little. Choose tough shade plants.

Is white alder native to California?

Yes, it is native to moist canyons on the West Coast. It grows in many plant communities along streams. It suits creekside restoration.

Can white alder grow in wet, poorly drained soil?

Yes, it tolerates no drainage, seasonal flooding, sand and clay. It even grows in creek beds. Use it for wet spots.

More plant watering guides

Soft Shield FernBlack CottonwoodCarolina PoplarOrnamental RhubarbWeeping WillowPeking WillowWillowStevia

Sources