WateringTimesWatering plan, $19
Quercus phellos, WUCOLS IV

How often to water willow oak in California

In July on the north-central coast, established willow oak in loam needs a deep watering about every 13 days: about 55 gallons each time under a 10 foot canopy, about 29 gallons a week. Willow oak is a fast-growing, long-lived deciduous oak from the eastern United States. Its narrow, willow-like leaves give it a fine texture, and it typically reaches 40 to 75 feet with a rounded crown. In the wild it grows beside swamps and streams, and it handles medium to wet soils, including clay, as long as they drain.

TreeRated for 2 of 6 zones

How often to water willow oak, 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 willow oak 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

  • Ground dry 18 inches below the surface under a young willow oak in summer means it is time for a long soak
  • Narrow leaves curling and browning at the tips in heat can indicate drought stress
  • A crown that sheds leaves weeks ahead of autumn has probably run short of moisture
  • Thin, yellow growth where water pools for days around the trunk suggests the soil drains poorly

How to water it

  • Lay soakers across the full spread of the crown, leaving the trunk itself dry
  • Give young trees a slow soak that reaches 18 inches to 2 feet, then wait for the top few inches to dry
  • Plant in acidic to average soil, from medium to moist, in full sun to light shade
  • Mulch widely instead of running lawn to the trunk
  • Move emitters outward as the crown spreads each year

Through the seasons

Water a young willow oak deeply and regularly through its first summers, since it naturally grows near water. Established trees still benefit from deep summer soaks in long dry spells. It is deciduous and transplants easily thanks to a fibrous root system. Winter rain usually covers its dormant season. WUCOLS rates willow oak moderate water on the north-central coast and on the south coast. WUCOLS has not evaluated it for the Central Valley, South Inland, the high desert or the low desert.

In pots

Willow oak is a large shade tree and does not stay long in a container. A young tree can grow for a season or two in a deep pot of well-drained mix. Water once the top two inches are dry, soaking until water runs out below. In summer heat, check every couple of days. Empty the saucer afterward. After leaf drop, water lightly through winter, then plant it out while still small.

1 Your climate zone six WUCOLS zones, each from its own reference city
Not ratedWUCOLS does not rate Willow Oak for the Central Valley zone
A year
no figure
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses

WUCOLS lists Willow Oak as not evaluated for the Central Valley zone, so no monthly figure is computed here.

Monthly water need by climate zone

Willow Oak: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.37–0.78–––
Feb0.53–0.81–––
Mar0.87–1.15–––
Apr1.18–1.4–––
May1.46–1.61–––
Jun1.61–1.74–––
Jul1.61–1.98–––
Aug1.49–1.86–––
Sep1.24–1.49–––
Oct0.87–1.15–––
Nov0.47–0.84–––
Dec0.31–0.65–––
Year12–15.5–––

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 not evaluated in the Central Valley, like willow oak. Plants that drink alike can share one valve and one schedule.

Hawthorn MapleAcer crataegifoliumnot rated, Central Valleyno Central Valley ratingMountain MapleAcer glabrumnot rated, Central Valleyno Central Valley ratingMiyabe MapleAcer miyabeinot rated, Central Valleyno Central Valley ratingEverglades PalmAcoelorraphe wrightiinot rated, Central Valleyno Central Valley ratingPink CedarAcrocarpus fraxinifoliusnot rated, Central Valleyno Central Valley ratingYellowwoodAfrocarpus falcatus (Podocarpus falcatus)not rated, Central Valleyno Central Valley ratingNew Caledonian PineAraucaria columnaris (A. cookii)not rated, Central Valleyno Central Valley ratingFormosa Sugar PalmArenga englerinot rated, Central Valleyno Central Valley ratingNeemAzadirachta indicanot rated, Central Valleyno Central Valley ratingBismarck PalmBismarckia nobilisnot rated, Central Valleyno Central Valley ratingAmerican HornbeamCarpinus caroliniananot rated, Central Valleyno Central Valley ratingJapanese HornbeamCarpinus japonicanot rated, Central Valleyno Central Valley ratingAmerican YellowwoodCladrastis kentukeanot rated, Central Valleyno Central Valley ratingPagoda DogwoodCornus alternifolianot rated, Central Valleyno Central Valley ratingGiant DogwoodCornus controversanot rated, Central Valleyno Central Valley ratingButterfly PalmDypsis lutescens (Areca)not rated, Central Valleyno Central Valley rating
Minutes for your sprinklers

Turn this into minutes on your water days

Every city page has a calculator that takes willow oak, 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 much water does willow oak need per day?

In July on the north-central coast, established willow oak needs about 4.1 gallons a day under a 10 foot canopy and about 16 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 willow oak change across California?

Yes. WUCOLS rates willow oak separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, not evaluated in the Central Valley zone, moderate water in the South Coastal zone, not evaluated in the South Inland zone, not evaluated 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.

How big does willow oak get?

It typically grows 40 to 75 feet tall and 25 to 50 feet wide, sometimes taller. It is long-lived. Give it room as a shade tree.

Is willow oak easy to transplant?

Yes, its fibrous root system makes it transplant better than many oaks. Water deeply after planting. Keep the root ball moist the first summer.

Can willow oak grow near a pond?

Yes, it naturally grows near swamps and streams and handles moist soil. It also does well in clay. Avoid soil that stays waterlogged.

Is willow oak good for wildlife?

Yes, its acorns feed birds and mammals once the tree is 15 to 20 years old. It is a high-value wildlife tree. It is toxic to horses.

Is willow oak a good street tree?

It is used for streets, parks and large yards and tolerates urban pollution. Its fine texture and rounded crown make good shade. Give the roots space.

More plant watering guides

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Sources