WateringTimesWatering plan, $19
Juglans regia ssp. & cvs., WUCOLS IV

How often to water English walnut in California

In July in the Central Valley, established English walnut 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. English walnut is a large deciduous tree grown across California for its edible nuts and broad, dense canopy. It sends down a deep taproot early, letting an established tree draw on moisture far below the surface. That same taproot makes it hard to move once planted, so give a young tree its permanent spot from the start.

TreeRated for 4 of 6 zones

How often to water English walnut, 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 English walnut 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

  • A dry, pale patch of soil at the edge of a young walnut's root ball is a cue to water
  • Leaflets drooping and dull in the afternoon heat can indicate a thirsty young tree
  • Sparse, undersized leaves through spring on an older tree warrant a closer look at soil moisture
  • Dark, wet bark at the trunk base with thinning upper foliage can indicate overwatering and root or crown rot
  • Premature yellow leaf drop in late summer on an otherwise healthy tree does not by itself establish thirst

How to water it

  • Water a young walnut over its full root ball and just beyond, moving the wet area outward as roots spread
  • Apply water with drip lines or a gentle trickle instead of a hose aimed at the trunk, keeping the crown dry
  • Keep the root crown and lower trunk dry between waterings to guard against root and crown rot
  • Choose a well-drained planting site, or mound the soil where natural drainage is slow
  • Water mature trees less often than young ones, checking soil moisture at depth before another soak

Through the seasons

A newly planted English walnut needs steady moisture while its taproot and side roots extend into surrounding soil. Established trees are deciduous, dropping their leaves in fall and using little water through winter dormancy. Summer irrigation matters most while the canopy is fully leafed out and producing nuts. WUCOLS rates English walnut moderate water on the north-central coast, on the south coast and in South Inland. It rates low water in the Central Valley. WUCOLS marks it as not suited to the high desert. WUCOLS marks it as not suited to the low desert. Winter rain often covers dormant coastal trees, but keep the root crown from sitting in soaked soil whenever rain is frequent.

In pots

A young English walnut develops a deep taproot early, so it belongs in a tall container only for its first year or two before planting in the ground. Check the potting mix several inches down through summer heat, since a shallow check misses how the taproot zone is drying. Let water drain fully through the holes and empty the saucer so roots do not sit wet. Keep the trunk base dry rather than pooling water against it. In winter, water only when the mix has dried, since the leafless tree uses very little moisture then.

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
0.631.31.92.50.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.631.31.92.50.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

English Walnut: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.160.780.78––
Feb0.530.260.810.87––
Mar0.870.431.151.3––
Apr1.180.611.41.61––
May1.460.831.611.95––
Jun1.610.991.742.29––
Jul1.611.071.982.51––
Aug1.490.951.862.33––
Sep1.240.721.491.86––
Oct0.870.471.151.33––
Nov0.470.220.840.9––
Dec0.310.140.650.68––
Year126.8415.518.41––

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 English walnut. 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 English walnut, 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 English walnut in summer?

In July, established English walnut in loam needs a deep watering about every 20 days in the Central Valley, about every 11 days on the south coast and about every 9 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 English walnut need per day?

In July in the Central Valley, established English walnut 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 English walnut change across California?

Yes. WUCOLS rates English walnut separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, low water in the Central Valley zone, moderate water in the South Coastal zone, moderate 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.

Why are my walnut tree's lower leaves turning yellow and dropping?

Check the soil at the drip line for constant dampness, since that favors root and crown rot. Bark that looks dark or wet near the base supports that concern. Dry, dusty soil points toward thirst instead, especially in a young tree.

How do I water a walnut tree without causing crown rot?

Keep irrigation water away from the trunk and lower bark. Let the top of the root zone dry somewhat between soakings. Walnuts planted on a slight mound drain better where soil is heavy.

Does an English walnut need water once it is mature?

A large, established tree still needs summer soil moisture around its wide root area for a full nut crop. Watch for wilted or scorched leaflets during heat as a cue. Deep, spaced-out soaks reach the root system better than light sprinkling.

Can I grow English walnut in a container long term?

Its deep taproot makes long-term container life difficult. Plan on moving a young tree to open ground within its first couple of years. A crowded root system in a pot struggles compared with one open to deeper soil.

Why does my walnut tree drop nuts early?

Check the root zone at depth rather than only the surface. Reviewing recent watering alongside pest and heat conditions helps narrow the cause.

More plant watering guides

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Sources