How often to water white ash in California
In July in the Central Valley, established white ash in loam needs a deep watering about every 8 days: about 55 gallons each time under a 10 foot canopy, about 47 gallons a week. White ash is a fast-growing deciduous shade tree from eastern North America and Mexico, usually 60 to 90 feet tall. Its compound leaves, dark green above and whitish beneath, turn yellow with purple tints in fall. It grows best in rich, moist, well-drained soil, and like most ashes it does best with regular watering.
How often to water white ash, 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
- A soil probe that stops at dry ground 8 to 12 inches down under the crown in summer calls for a long soak
- Wilting, dying branches while the soil is still moist can point to verticillium wilt rather than thirst
- Yellowing leaves over waterlogged ground point to poor drainage, since it grows best in well-drained soil
- Spotted, distorted spring leaves after a wet spell point to anthracnose, not to a lack of water
- Winged seeds littering paths come from female trees and are not a sign of stress
How to water it
- Give deep, regular soakings through summer, wetting the soil about 18 inches down
- Spread water widely under and beyond the canopy as the tree grows
- Plant in rich, moist, well-drained soil, in sun or shade
- Keep it away from salty coastal air, which it does not tolerate
- Choose a male tree if you want to avoid seed litter near walks
Through the seasons
Water a young tree regularly through its first summers while roots spread. Small flowers appear before the leaves in spring, and the leaves color yellow and purple in fall. Female trees hang clusters of winged seeds from late summer into winter. Established trees still want regular deep watering through the dry summer. Winter rain usually covers the bare tree on the north-central coast and in the Central Valley. WUCOLS rates white ash moderate water on the north-central coast and in the Central Valley. WUCOLS marks it as not suited to the south coast, South Inland, the high desert or the low desert.
In pots
White ash becomes a very large tree, so it belongs in a container only as a young sapling before planting out. It transplants easily, which makes the move simple. Use a deep pot with drainage holes and a rich, well-drained mix. On hot days, check the mix 2 inches down and water once it is dry there. Let water drain, then empty the saucer, and plant it in the ground within a season or two.
- A year
- 17.11 gal per sq ft
- Reference
- Sacramento climate table
- Counts
- Plant need, before sprinkler losses
Monthly water need by climate zone
White Ash: gallons per square foot per month, by WUCOLS climate zone
| Month | N. Coast | C. Valley | S. Coast | S. Inland | Hi Desert | Lo Desert |
|---|---|---|---|---|---|---|
| Jan | 0.37 | 0.4 | – | – | – | – |
| Feb | 0.53 | 0.65 | – | – | – | – |
| Mar | 0.87 | 1.09 | – | – | – | – |
| Apr | 1.18 | 1.52 | – | – | – | – |
| May | 1.46 | 2.08 | – | – | – | – |
| Jun | 1.61 | 2.48 | – | – | – | – |
| Jul | 1.61 | 2.67 | – | – | – | – |
| Aug | 1.49 | 2.39 | – | – | – | – |
| Sep | 1.24 | 1.8 | – | – | – | – |
| Oct | 0.87 | 1.18 | – | – | – | – |
| Nov | 0.47 | 0.56 | – | – | – | – |
| Dec | 0.31 | 0.34 | – | – | – | – |
| Year | 12 | 17.11 | – | – | – | – |
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 moderate water in the Central Valley, like white ash. Plants that drink alike can share one valve and one schedule.
Citrus TreesCitrus spp.moderate water, Central Valley2.67 gal/sq ft in July
Japanese MapleAcer palmatummoderate water, Central Valley2.67 gal/sq ft in July
Avocado TreesPersea americanamoderate water, Central Valley2.67 gal/sq ft in July
Magnolia TreesMagnolia grandiflora ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in July
Palm TreesSyagrus romanzoffiana (Arecastrum romanzoffianum)moderate water, Central Valley2.67 gal/sq ft in July
Apple TreesMalus spp. (edible) e.g, 'Anna' (low chill variety for low desert)moderate water, Central Valley2.67 gal/sq ft in July
Peach TreesPrunus spp. ediblemoderate water, Central Valley2.67 gal/sq ft in July
Persimmon TreesDiospyros kakimoderate water, Central Valley2.67 gal/sq ft in July
Amur MapleAcer ginnalamoderate water, Central Valley2.67 gal/sq ft in July
Fernleaf MapleAcer japonicummoderate water, Central Valley2.67 gal/sq ft in July
Box ElderAcer negundomoderate water, Central Valley2.67 gal/sq ft in July
Norway MapleAcer platanoidesmoderate water, Central Valley2.67 gal/sq ft in July
Red MapleAcer rubrummoderate water, Central Valley2.67 gal/sq ft in July
Chinese MapleAcer truncatummoderate water, Central Valley2.67 gal/sq ft in July
Red BuckeyeAesculus paviamoderate water, Central Valley2.67 gal/sq ft in July
Red HorsechestnutAesculus x carneamoderate water, Central Valley2.67 gal/sq ft in JulySimilar plants that need less water 16
Rated lower than white ash in the Central Valley. Worth a look for a new bed or a lawn replacement.
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
Portuguese OakQuercus faginealow 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 JulyTurn this into minutes on your water days
Every city page has a calculator that takes white ash, 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 white ash need per day?
In July in the Central Valley, established white ash needs about 6.8 gallons a day under a 10 foot canopy and about 27 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 white ash change across California?
Yes. WUCOLS rates white ash separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, moderate water in the Central Valley zone, not suited to this region in the South Coastal zone, not suited to this region 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.
Why does my white ash drop so many seeds?
Only female trees make seeds, in drooping clusters of winged samaras that ripen from late summer and can hang on through winter. They can be a nuisance near walkways. Male trees produce no seeds.
Are white ash branches brittle?
Yes. Its branches can break in high winds and under heavy loads. Keep large limbs away from roofs and have weak ones removed.
What pests attack white ash?
Borers, scales, leaf miners and aphids can all appear, along with anthracnose, leaf spots and verticillium wilt. Check the bark and leaves before blaming water.
Can white ash grow in shade?
Yes. It grows in full sun to shade and in many soil types. It does best in rich, moist soil with good drainage.
How big does white ash get?
It usually grows fast to 60 to 90 feet tall and 50 to 75 feet wide, and old trees can top 100 feet. Plant it only where it has plenty of room.
More plant watering guides
Sources
- WUCOLS IV plant water use classification for Fraxinus americana, 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