WateringTimesWatering plan, $19
Quercus suber, WUCOLS IV

How often to water cork oak in California

In July in the Central Valley, established cork oak in loam needs a deep watering about every 20 days: about 55 gallons each time under a 10 foot canopy, about 19 gallons a week. Cork oak is a broad, round-headed evergreen tree known for its thick, deeply fissured, corky gray bark. Established trees are drought tolerant and handle long dry stretches once settled into the ground. A young tree still needs regular soakings while its roots spread.

TreeRated for 6 of 6 zones

How often to water cork 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 cork 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

  • Dry, pale soil pulling away from a young cork oak's root ball calls for a deep soak
  • Leaves curling and dulling through a hot first summer in the ground can indicate a young tree needs water
  • An established tree holding its canopy through a long rainless summer is normal for this species, not a sign of stress
  • Thinning foliage and soft, blackened bark near the base over wet soil can indicate root rot
  • Cracking or peeling in the thick corky bark is a mature feature of this tree, not a cue about watering

How to water it

  • Give a newly planted cork oak regular soakings across its root ball while its roots spread into the surrounding soil
  • Stretch out the time between waterings as the tree settles in, checking depth rather than counting days
  • Choose a planting site with fast drainage, since wet, heavy soil threatens this tree's roots more than dry spells do
  • Run drip emitters a few feet out from the trunk rather than directly against it
  • Expect an established tree to need little beyond winter rain in most years

Through the seasons

A newly planted cork oak needs regular soakings through its first couple of summers while its deep root system develops. Established trees are evergreen year round and tolerate long dry stretches, often needing little more than winter rain to get through the cool season. Watering an older tree matters most during extended summer heat rather than on any fixed schedule. Winter rain can cover the dormant season across most of the state where this tree grows. WUCOLS rates cork oak low water in all six of California's climate zones: the north-central coast, the Central Valley, the south coast, South Inland, the high desert and the low desert.

In pots

Cork oak adapts to container life for its first few years, though its vigorous roots eventually call for open ground. Feel the mix several inches down through California's dry months, since a planted bed holds moisture far longer than a pot. Water until it runs through the drainage holes, then tip out the saucer so the roots are not left standing in it. A fast-draining, slightly acidic mix suits this species better than a rich, moisture-holding one. In winter, this evergreen needs only occasional water as its growth slows.

1 Your climate zone six WUCOLS zones, each from its own reference city
1.07gal per sq ft in JulyLow water use in the Central Valley zone
A year
6.84 gal per sq ft
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses
0.300.610.921.20.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.300.610.921.20.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

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

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.150.160.310.310.30.31
Feb0.210.260.320.350.370.37
Mar0.350.430.460.520.580.61
Apr0.470.610.560.640.760.78
May0.580.830.640.780.950.98
Jun0.640.990.690.921.141.12
Jul0.641.070.7911.221.14
Aug0.60.950.740.931.121.04
Sep0.50.720.60.740.860.83
Oct0.350.470.460.530.580.6
Nov0.190.220.330.360.370.38
Dec0.120.140.260.270.260.27
Year4.86.846.27.378.518.43

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 low water in the Central Valley, like cork oak. Plants that drink alike can share one valve and one schedule.

Olive TreesOlea europaea ssp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyFig TreesFicus carica 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 JulyAloeAloe spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyPomegranate TreesPunica granatumlow water, Central Valley1.07 gal/sq ft in JulyEucalyptusEucalyptus polyanthemoslow water, Central Valley1.07 gal/sq ft in JulyPine TreesPinus canariensislow water, Central Valley1.07 gal/sq ft in JulyJunipersJuniperus spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyTexas Red OakQuercus buckleyilow water, Central Valley1.07 gal/sq ft in JulyPortuguese OakQuercus faginealow water, Central Valley1.07 gal/sq ft in JulySoapbark TreeQuillaja saponarialow water, Central Valley1.07 gal/sq ft in JulyNecklace TreeSophora affinislow water, Central Valley1.07 gal/sq ft in JulyBailey AcaciaAcacia baileyanalow water, Central Valley1.07 gal/sq ft in JulySilver WattleAcacia dealbatalow water, Central Valley1.07 gal/sq ft in JulyGreen WattleAcacia decurrenslow water, Central Valley1.07 gal/sq ft in JulySydney Golden WattleAcacia longifolialow 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 cork 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 often should I water cork oak in summer?

In July, established cork oak in loam needs a deep watering about every 20 days in the Central Valley, about every 27 days on the south coast and about every 22 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 cork oak need per day?

In July in the Central Valley, established cork oak needs about 2.7 gallons a day under a 10 foot canopy and about 11 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 cork oak change across California?

Yes. WUCOLS rates cork oak separately for each of the six California climate zones: low water in the North-Central Coastal zone, low water in the Central Valley zone, low water in the South Coastal zone, low water in the South Inland zone, low water in the High and Intermediate Desert zone, low water in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

How much water does an established cork oak need?

Very little in most of the state, since WUCOLS rates it low water in every climate zone. An established tree is drought tolerant and can go long stretches without irrigation. Occasional deep soaking during extended summer heat still helps a mature tree.

Why does cork oak have such thick bark?

The thick, corky bark is a natural insulating layer that also makes this species notably fire resistant. Growers harvest it for cork products once a tree reaches several decades of age. This bark feature has no bearing on how the tree is watered.

Can cork oak grow in average garden soil?

Yes, it tolerates a range of well-drained soils, though it favors slightly acidic ground. Heavy, slow-draining clay is the condition to avoid. Improving drainage before planting helps more than extra watering afterward.

Does a young cork oak need frequent watering?

Yes, a newly planted tree needs more regular soakings than an established one while its roots reach deeper soil. Expect to water more often through its first couple of summers. Taper off gradually as the tree settles in.

Is cork oak the source of real wine cork stoppers?

Yes, cork oak bark is the traditional source of cork used in wine stoppers and other products. Commercial harvesting does not apply to a typical landscape tree. A home garden specimen is grown mainly for its form and shade.

More plant watering guides

GeraniumsOlive TreesFig TreesCrape MyrtleWisteriaLantanaSalviaIrises

Sources