How often to water Portuguese oak in California
In July in the Central Valley, established Portuguese 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. Portuguese oak is a tree from Spain and Portugal that can reach 70 feet, with thick gray-brown bark broken into squarish blocks. Its leathery, toothed leaves, 1 to 3 inches long, are gray-green above and gray-felted beneath, and they usually hang on through winter. Like other oaks it bears acorns, and it rates low water in the Central Valley.
How often to water Portuguese oak, month by month
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.
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.
How to tell it needs water
- On a young tree, soil dry 6 inches down under the canopy in summer calls for one slow, deep soak
- Leaves hanging on into winter are normal for this oak, not a sign of drought
- Yellowing leaves and dieback in soil kept wet through summer point to too much water for a low-water oak
- Leaves that differ in shape and toothing from tree to tree are normal, since this species is very variable
How to water it
- Water a young tree deeply at the edge of its root zone, wetting the soil about 18 inches down
- Once it is established, give only occasional deep soaks in summer, letting the soil dry well between them
- Plant it where it has room to grow into a large tree
- Mulch the root zone instead of planting thirsty lawn under the canopy
- Widen the watering circle as the canopy spreads
Through the seasons
Water a young tree regularly through its first two or three summers, then taper off. Its leathery leaves usually stay on through winter, and new shoots appear in spring. Winter rain usually covers it in the Central Valley, and established trees need only occasional deep summer soaks there. WUCOLS rates Portuguese oak low water in the Central Valley. WUCOLS has not evaluated it for the north-central coast, the south coast, South Inland, the high desert or the low desert.
In pots
Portuguese oak grows into a large tree, so a container suits only a young seedling waiting to be planted. Use a deep pot with drainage holes and a well-drained mix. In summer, check the mix 2 inches down every few days and water when it is dry there. Let water drain through, then empty the saucer. Plant it in the ground while it is small, before roots circle the pot.
- A year
- 6.84 gal per sq ft
- Reference
- Sacramento climate table
- Counts
- Plant need, before sprinkler losses
Monthly water need by climate zone
Portuguese Oak: gallons per square foot per month, by WUCOLS climate zone
| Month | N. Coast | C. Valley | S. Coast | S. Inland | Hi Desert | Lo Desert |
|---|---|---|---|---|---|---|
| Jan | – | 0.16 | – | – | – | – |
| Feb | – | 0.26 | – | – | – | – |
| Mar | – | 0.43 | – | – | – | – |
| Apr | – | 0.61 | – | – | – | – |
| May | – | 0.83 | – | – | – | – |
| Jun | – | 0.99 | – | – | – | – |
| Jul | – | 1.07 | – | – | – | – |
| Aug | – | 0.95 | – | – | – | – |
| Sep | – | 0.72 | – | – | – | – |
| Oct | – | 0.47 | – | – | – | – |
| Nov | – | 0.22 | – | – | – | – |
| Dec | – | 0.14 | – | – | – | – |
| Year | – | 6.84 | – | – | – | – |
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 Portuguese 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 July
Fig TreesFicus carica ssp. & cvs.low water, Central Valley1.07 gal/sq ft in July
Crape MyrtleLagerstroemia spp., hybrids & cvs.low water, Central Valley1.07 gal/sq ft in July
AloeAloe spp. & cvs.low water, Central Valley1.07 gal/sq ft in July
Pomegranate TreesPunica granatumlow water, Central Valley1.07 gal/sq ft in July
EucalyptusEucalyptus polyanthemoslow water, Central Valley1.07 gal/sq ft in July
Pine TreesPinus canariensislow water, Central Valley1.07 gal/sq ft in July
JunipersJuniperus spp. & cvs.low water, Central Valley1.07 gal/sq ft in July
Texas Red OakQuercus buckleyilow water, Central Valley1.07 gal/sq ft in July
Soapbark TreeQuillaja saponarialow water, Central Valley1.07 gal/sq ft in July
Necklace TreeSophora affinislow water, Central Valley1.07 gal/sq ft in July
Bailey AcaciaAcacia baileyanalow water, Central Valley1.07 gal/sq ft in July
Silver WattleAcacia dealbatalow water, Central Valley1.07 gal/sq ft in July
Green WattleAcacia decurrenslow water, Central Valley1.07 gal/sq ft in July
Sydney Golden WattleAcacia longifolialow water, Central Valley1.07 gal/sq ft in July
Blackwood AcaciaAcacia melanoxylonlow water, Central Valley1.07 gal/sq ft in JulyTurn this into minutes on your water days
Every city page has a calculator that takes Portuguese 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 Portuguese oak need per day?
In July in the Central Valley, established Portuguese 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 Portuguese oak change across California?
Yes. WUCOLS rates Portuguese oak separately for each of the six California climate zones: not evaluated in the North-Central Coastal zone, low water in the Central Valley zone, not evaluated 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.
Is Portuguese oak evergreen?
Partly. Its leathery leaves usually persist on the tree through winter. New growth replaces them in spring.
How big does Portuguese oak get?
It can grow into a tree up to 70 feet tall, though it occasionally stays shrubby. Give it plenty of room.
Where does Portuguese oak come from?
It is native to Spain and Portugal and possibly North Africa. It has been grown in gardens since 1835.
Why do Portuguese oak leaves look so different from tree to tree?
It is an exceedingly variable species, with leaves that differ in size, shape and toothing. Some forms keep a gray felt under the leaves, while others become almost smooth.
Can you overwater Portuguese oak?
Yes. In the Central Valley it is a low-water tree once established. Water deeply but rarely, and let the soil dry well between soakings.
More plant watering guides
Sources
- WUCOLS IV plant water use classification for Quercus faginea, the University of California survey California agencies use for landscape plan reviewRead August 23, 2026 on wucols.ucdavis.edu
- Model Water Efficient Landscape Ordinance, adopted text and appendices, effective 2025-01-02 · monthly reference evapotranspiration per city, Appendix CRead August 23, 2026 on water.ca.gov/-/media/DWR-Website/Web-Pages/Programs/Water-Use-And-Efficiency/MWELO-Rulemaking/Final-MWELO-Text-and-Appendices_20250103.pdf
- UC Statewide IPM Program, irrigation scheduling using evapotranspirationRead September 30, 2026 on ipm.ucanr.edu/PMG/GARDEN/ENVIRON/evap.html
- Shaw and Pittenger, Landscape Irrigation System Evaluation and Management, UC Cooperative Extension, 2009Read September 30, 2026 on ucanr.edu/sites/default/files/2013-02/160836.pdf
- Pittenger, Water Management in Gardens and Landscapes, UC Riverside, 2017Read September 30, 2026 on ucanr.edu/sites/default/files/2017-03/258022.pdf