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WateringTimes

Olea europaea ssp. & cvs. · WUCOLS

How Often to Water Olive Trees in California

Computed August 26, 2026 from WUCOLS and adopted state reference data

Established olive trees rate as low water plants in the Central Valley: about 1.07 gallons per square foot in July and 6.84 gallons per square foot per year, before irrigation losses. Olive trees are among the most drought tolerant trees you can plant in a California yard. They come from the dry Mediterranean and rate low water use in every part of the state. An established tree wants deep, infrequent soakings at the drip line and soil that drains freely, and steady wet ground harms it far more than a dry spell.

Your climate zone

Olive Trees: low water use in the Central Valley zone

About 1.07 gallons per square foot in July and 6.84 gallons per square foot over a full year, using Sacramento as the zone reference city. These are plant needs before irrigation system losses.

Monthly water need by climate zone

Olive Trees: gallons per square foot per month, by WUCOLS climate zone

Six climate zones, one row per month. The table scrolls sideways on a narrow screen; the month column stays put.

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

Computed as the WUCOLS class midpoint for Olea europaea ssp. & cvs. times monthly reference evapotranspiration for each zone's reference city (N. Coast: San Francisco, C. Valley: Sacramento, S. Coast: Los Angeles, S. Inland: Riverside, Hi Desert: Victorville, Lo Desert: Palm Springs) times 0.62. A dash means WUCOLS does not rate this plant for that zone. Values are plant needs before irrigation system losses. Cool-season values are usually covered by rain, and dormant or deciduous plants often need no irrigation at all in winter; see Through the seasons below.

How to tell it needs water

  • Soil dry 2 to 3 inches down at the drip line means an established tree is ready for a deep soak
  • Leaves that fold inward along the midrib or turn a dull gray are showing drought stress
  • Shriveled or dropping fruit in summer heat on a fruiting variety points to water stress
  • Yellow leaves that drop while the soil stays damp signal overwatering or poor drainage, not thirst
  • Heavy leaf drop over soggy ground means roots are suffocating, so let the soil dry out

How to water it

  1. Water in a wide ring near the drip line, not against the trunk, since that is where the feeder roots are
  2. Use drip emitters or a slow hose trickle, and move the ring outward as the canopy grows
  3. Soak deeply so water reaches the whole root zone, then let the soil dry before the next watering
  4. Keep the trunk base dry, and hold mulch back from the bark while spreading it out toward the drip line
  5. In heavy clay, split a soaking into slow cycles so water sinks in instead of running off, and wait longer between waterings

In pots

A potted olive lives by different rules than one in the ground. The container holds a small root zone that dries fast in summer heat, so check it often and water when the top few inches of mix are dry, until water runs from the drainage holes. Never leave the pot standing in a saucer of water, because trapped moisture rots olive roots quickly. A container tree also cannot ride out a dry spell the way an established tree in the ground can, so do not treat it as drought proof.

Through the seasons

An olive tree's needs follow California's dry summer rhythm. Winter rain usually covers the cool months in coastal and valley areas, and irrigation matters mainly from late spring through early fall, when the soil dries out and fruiting trees are setting and sizing their crop. Young trees are the exception: keep them on regular deep soakings through the first summer and taper off as the roots spread, because a tree is not established until its roots reach well past the planting hole. A mature olive rates low water use even in the deserts, but the long hot season there means the warm months still carry nearly all of the year's watering.

Questions people ask

How much water do olive trees need in summer?
In July, an established planting needs roughly this many gallons per square foot: 0.64 in the North-Central Coastal zone, 1.07 in the Central Valley zone, 0.79 in the South Coastal zone, 1 in the South Inland zone, 1.22 in the High and Intermediate Desert zone, 1.14 in the Low Desert zone. Figures are computed from the WUCOLS rating for Olea europaea ssp. & cvs. and each zone's reference evapotranspiration, and they are plant needs before irrigation system losses.
Does watering for olive trees change across California?
Yes. WUCOLS rates olive trees 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.
Can you overwater an olive tree?
Yes, and it is the most common mistake with landscape olives. Roots sitting in wet soil suffocate and invite root rot: leaves yellow and drop, growth stalls, and branches can die back even though the tree is getting plenty of water. Let the soil dry well between deep soakings and fix any drainage problem before adding more water.
How often should I water a newly planted olive tree?
Keep the root ball evenly moist through the first summer while roots grow into the surrounding soil. Check the top of the root zone in warm weather and soak deeply whenever it dries. From the second growing season, stretch the intervals and water a wider ring, until the established tree needs only occasional deep soakings in the warm months.
Is drip irrigation good for olive trees?
Drip suits olives well. Place emitters in a ring near the drip line rather than against the trunk, then add emitters and move the ring outward as the canopy grows. Run the system long enough to wet the soil deep into the root zone, then let it dry before the next cycle. Short frequent runs keep roots shallow and the surface damp, which olives dislike.
Should I water an olive tree in winter in California?
Usually not if it is in the ground. Winter rain covers the cool season in most of the state, and the tree slows down then and takes up little water. Step in only during a long dry warm spell, and keep checking containers, which dry out even in winter.
Why is my olive tree turning yellow or dropping leaves?
Check the soil first. Yellow leaves over damp ground point to overwatering or poor drainage, the top cause of olive decline in gardens. Olives also shed some of their oldest inner leaves naturally, mostly in spring, so a light drop on an otherwise healthy tree is normal. A thirsty tree looks different: dull gray, folded leaves above soil that is dry deep down.
Does watering affect olive fruit?
Yes. Drought stress around bloom and fruit set makes a tree drop fruit, and dry midsummer soil leads to small, shriveled olives. Deep soakings through the heat improve fruit size on fruiting varieties. If you grow a fruitless landscape cultivar, the tree can stay drier, since fruit quality is not a concern and the tree itself handles drought well.

More plant watering guides

Sources

WateringTimes is an informational gardening and landscape reference for California. Watering numbers are estimates computed from public state data. Nothing on this site is regulatory or professional advice of any kind. Check your water supplier’s current rules before relying on any schedule.