WateringTimesWatering plan, $19
Ulmus americana, WUCOLS IV

How often to water American elm in California

In July in the Central Valley, established American elm 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. American elm is a fast-growing deciduous shade tree from eastern North America, 60 to 80 feet tall with a classic vase shape. Its leaves turn soft yellow in fall. Like most elms it is adapted to summer rain, so dry California summers call for deep irrigation. It is also highly susceptible to Dutch elm disease.

TreeRated for 4 of 6 zones

How often to water American elm, 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 American elm 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 soil probe meeting dry ground 12 inches deep beneath the branches in midsummer means the elm is due for a long, slow soak
  • Leaves yellowing and wilting in one part of the crown, then browning but hanging on, point to Dutch elm disease rather than thirst
  • Leaves riddled with holes or skeletonized point to elm leaf beetle, not drought
  • Wet, oozing streaks on the trunk point to wetwood, a bacterial problem rather than an irrigation one
  • Roots surfacing in a lawn point to frequent shallow sprinkling, since elms tend to root shallowly

How to water it

  • Run slow, deep irrigation in the dry months until moisture reaches at least 18 inches
  • Spread water broadly across the root zone, since elms tend to be shallow rooted
  • Plant in full sun or part shade in well-drained soil of average moisture
  • Prune only when needed, in late fall or winter, and remove dead limbs promptly
  • Choose a selection resistant to Dutch elm disease, and widen watering as the canopy spreads

Through the seasons

Water a young tree regularly through its first summers while roots spread. Elms are adapted to summer rain, so established trees still need deep, regular irrigation through California's dry season to stay vigorous. Small flowers appear in late winter, winged seeds follow in spring, and the leaves turn soft yellow before dropping in fall. From late fall to spring, rain normally carries the leafless tree along the coast and in the Central Valley. On the north-central coast, in the Central Valley, on the south coast and in South Inland, American elm rates moderate water. WUCOLS has not evaluated it for the high desert. WUCOLS marks it as not suited to the low desert.

In pots

American elm becomes a very large tree, so a container suits only a young sapling before planting. Its fibrous roots make it easy to move into the ground later. Grow it in a tall nursery container with open holes and a free-draining mix. Through warm weather, feel the mix 2 inches down every couple of days and water when it is dry there. Let excess drain, empty the saucer, and plant it out within a season or two.

1 Your climate zone six WUCOLS zones, each from its own reference city
2.67gal per sq ft in JulyModerate water use in the Central Valley zone
A year
17.11 gal per sq ft
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses
0.671.32.02.70.4JAN0.65FEB1.09MAR1.52APR2.08MAY2.48JUN2.67JUL2.39AUG1.8SEP1.18OCT0.56NOV0.34DEC0.671.32.02.70.4JFM1.52AMJ2.67JAS1.18OND
Gallons per square foot per month, Central Valley. Peak 2.67 in Jul, 17.11 a year.

Monthly water need by climate zone

American Elm: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.40.780.78––
Feb0.530.650.810.87––
Mar0.871.091.151.3––
Apr1.181.521.41.61––
May1.462.081.611.95––
Jun1.612.481.742.29––
Jul1.612.671.982.51––
Aug1.492.391.862.33––
Sep1.241.81.491.86––
Oct0.871.181.151.33––
Nov0.470.560.840.9––
Dec0.310.340.650.68––
Year1217.1115.518.41––

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 moderate water in the Central Valley, like American elm. Plants that drink alike can share one valve and one schedule.

Citrus TreesCitrus spp.moderate water, Central Valley2.67 gal/sq ft in JulyJapanese MapleAcer palmatummoderate water, Central Valley2.67 gal/sq ft in JulyAvocado TreesPersea americanamoderate water, Central Valley2.67 gal/sq ft in JulyMagnolia TreesMagnolia grandiflora ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyPalm TreesSyagrus romanzoffiana (Arecastrum romanzoffianum)moderate water, Central Valley2.67 gal/sq ft in JulyApple TreesMalus spp. (edible) e.g, 'Anna' (low chill variety for low desert)moderate water, Central Valley2.67 gal/sq ft in JulyPeach TreesPrunus spp. ediblemoderate water, Central Valley2.67 gal/sq ft in JulyPersimmon TreesDiospyros kakimoderate water, Central Valley2.67 gal/sq ft in JulyAmur MapleAcer ginnalamoderate water, Central Valley2.67 gal/sq ft in JulyFernleaf MapleAcer japonicummoderate water, Central Valley2.67 gal/sq ft in JulyBox ElderAcer negundomoderate water, Central Valley2.67 gal/sq ft in JulyNorway MapleAcer platanoidesmoderate water, Central Valley2.67 gal/sq ft in JulyRed MapleAcer rubrummoderate water, Central Valley2.67 gal/sq ft in JulyChinese MapleAcer truncatummoderate water, Central Valley2.67 gal/sq ft in JulyRed BuckeyeAesculus paviamoderate water, Central Valley2.67 gal/sq ft in JulyRed HorsechestnutAesculus x carneamoderate water, Central Valley2.67 gal/sq ft in July

Similar plants that need less water 16

Rated lower than American elm 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 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 American elm, 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 American elm in summer?

In July, established American elm in loam needs a deep watering about every 8 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 American elm need per day?

In July in the Central Valley, established American elm 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 American elm change across California?

Yes. WUCOLS rates American elm separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, moderate water in the Central Valley zone, moderate water in the South Coastal zone, moderate water in the South Inland zone, not evaluated 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 is my American elm wilting in one section?

Leaves that yellow and wilt in one part of the canopy, then brown and hang on, can mean Dutch elm disease. Brown streaks under the bark of a cut branch help confirm it. Have an arborist check the tree promptly, since the disease spreads to nearby elms.

Why are my elm leaves full of holes?

Elm leaf beetle chews holes in the leaves and skeletonizes their surfaces. From a distance the browning can look like Dutch elm disease, so inspect the leaves up close.

Are there disease-resistant elms?

Yes. Resistant selections such as 'Princeton' are available. Hackberry and hornbeam look similar and are not attacked by elm pests.

When should I prune American elm?

Avoid unnecessary pruning, and prune when needed in late fall or winter. Clean and sterilize tools between trees, and remove dead or dying limbs promptly.

Can American elm grow in wet soil?

Yes. It adapts to both wet and dry sites, though it grows best in well-drained soil with average moisture.

More plant watering guides

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Sources