WateringTimesWatering plan, $19
Notholithocarpus densiflorus (Lithocarpus densiflorus), WUCOLS IV

How often to water tanbark oak in California

In July on the north-central coast, established tanbark oak in loam needs a deep soak only about once a month or less: about 55 gallons each time under a 10 foot canopy. Tanbark oak is a California native evergreen tree that grows slowly, sometimes to 80 feet, though some plants stay shrubby. Its leathery, toothed leaves are dark olive green above and fuzzy tan beneath, and small white flowers in upright catkins lead to acorns. It grows wild in coastal mountain forests from southwestern Oregon to the ranges above Santa Barbara.

TreeCalifornia nativeRated for 3 of 6 zones

How often to water tanbark 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 tanbark 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

  • Soil dry a foot down around a young tree in its first summer means it needs a deep soak
  • Leaves yellowing or dropping heavily in a long hot spell on a young tree can signal thirst
  • Leaf edges browning in hot, dry wind suggest the site is too exposed
  • Yellowing leaves and dieback in soggy, poorly drained soil point to root problems

How to water it

  • Water a young tree deeply, then let the soil dry well between soakings
  • Water an established tree only in long dry spells
  • Plant in cool sun, part shade or shade in well-drained soil
  • Leave leaf litter under the canopy as natural mulch
  • Choose a cool, sheltered site rather than a hot, exposed one

Through the seasons

Water a young tree through its first few summers while roots grow deep. After that, it needs only occasional deep water in long dry spells. It stays evergreen and flowers in catkins before the acorns form. It does best in cool, coastal conditions, in sun, part shade or full shade. WUCOLS rates tanbark oak low water on the north-central coast, on the south coast and in South Inland. WUCOLS marks it as not suited to the Central Valley, the high desert or the low desert.

In pots

Tanbark oak grows slowly and can live in a large container for several years while young. Use a deep pot with a well-drained mix. Water when the top few inches are dry, then let all excess drain. In summer, check every few days and keep the pot out of hot afternoon sun. Do not let it stand in water. In winter, rain usually covers it, so water only in dry spells.

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

WUCOLS lists Tanbark Oak as not suited to this region for the Central Valley zone, so no monthly figure is computed here.

Monthly water need by climate zone

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

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.15–0.310.31––
Feb0.21–0.320.35––
Mar0.35–0.460.52––
Apr0.47–0.560.64––
May0.58–0.640.78––
Jun0.64–0.690.92––
Jul0.64–0.791––
Aug0.6–0.740.93––
Sep0.5–0.60.74––
Oct0.35–0.460.53––
Nov0.19–0.330.36––
Dec0.12–0.260.27––
Year4.8–6.27.37––

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 suited to this region in the Central Valley, like tanbark oak. Plants that drink alike can share one valve and one schedule.

Sugar MapleAcer saccharumnot rated, Central Valleyno Central Valley ratingQueensland KauriAgathis robustanot rated, Central Valleyno Central Valley ratingCherimoyaAnnona cherimolanot rated, Central Valleyno Central Valley ratingPurple Orchid TreeBauhinia variegata (purpurea)not rated, Central Valleyno Central Valley ratingToogBischofia javanicanot rated, Central Valleyno Central Valley ratingClustered Fishtail PalmCaryota mitisnot rated, Central Valleyno Central Valley ratingWhite SapoteCasimiroa edulisnot rated, Central Valleyno Central Valley ratingFilbertCorylus maximanot rated, Central Valleyno Central Valley ratingSpotted GumCorymbia maculata (Eucalyptus maculata)not rated, Central Valleyno Central Valley ratingDove TreeDavidia involucratanot rated, Central Valleyno Central Valley ratingRoyal PoincianaDelonix regianot rated, Central Valleyno Central Valley ratingTriangle PalmDypsis decaryinot rated, Central Valleyno Central Valley ratingMountain White GumEucalyptus dalrympleananot rated, Central Valleyno Central Valley ratingRainbow EucalyptusEucalyptus degluptanot rated, Central Valleyno Central Valley ratingRoxburgh FigFicus auriculatanot rated, Central Valleyno Central Valley ratingIndian BanyanFicus benghalensisnot 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 tanbark 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 tanbark oak in summer?

In July, established tanbark oak in loam needs a deep watering 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 tanbark oak need per day?

In July on the north-central coast, established tanbark oak needs about 1.6 gallons a day under a 10 foot canopy and about 6.5 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 tanbark oak change across California?

Yes. WUCOLS rates tanbark oak separately for each of the six California climate zones: low water in the North-Central Coastal zone, not suited to this region in the Central Valley zone, low water in the South Coastal zone, low 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.

Are tanbark oak acorns edible?

Its leached acorns were ground into flour by Native Americans. The flour tastes a little like bitter oatmeal. Acorns must be leached before eating.

Where does tanbark oak grow naturally?

It grows in forests of the coastal mountains from southwestern Oregon to the Transverse Ranges above Santa Barbara. It also occurs in the northern Sierra Nevada. Cool, coastal sites suit it best.

Why is it called tanbark oak?

Its bark was once used to tan hides for leather. Its botanical name has changed over the years. It may be sold under either name.

How big does tanbark oak get?

It grows slowly to 65 to 80 feet in good sites. Some plants stay shrubby. Give it room.

Can tanbark oak grow in shade?

Yes, it grows in cool sun, part shade or shade. A shady, sheltered spot suits it in warm areas. Keep the soil well drained.

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Sources