WateringTimesWatering plan, $19
Populus nigra 'Italica', WUCOLS IV

How often to water Lombardy poplar in California

In July in the Central Valley, established Lombardy poplar 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. Lombardy poplar is a narrow, columnar deciduous tree used as a fast-growing screen or windbreak. Shallow, suckering roots can lift paving and damage drains. Cytospora canker can kill this short-lived tree, and drought stress increases its susceptibility.

TreeRated for 6 of 6 zones

How often to water Lombardy poplar, 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 Lombardy poplar 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

  • Soil dry several inches down along the root run beneath a Lombardy poplar signals it needs a deep soak
  • Sunken, discolored patches oozing on the upper trunk or branches point to canker, which stressed, poorly watered trees are more prone to
  • Puddles expanding along an already wet poplar row during irrigation are a cue to stop adding water
  • A spread of new suckers in the lawn or bed nearby reflects this tree's root habit rather than a watering problem

How to water it

  • Spread emitters across the root area along the poplar row rather than concentrating water beside each trunk
  • Let an established row dry out several inches down between deep soakings rather than keeping the surface constantly damp
  • Mow or cut off suckers at ground level as soon as they appear in the row or nearby turf
  • Keep the trunk and lower bark dry when watering, since splashing moisture there can help canker spores take hold
  • Step up watering frequency for a desert row to match the higher rating WUCOLS gives those zones

Through the seasons

A newly planted row of Lombardy poplars needs frequent attention through its first couple of summers, since the shallow roots have not yet spread far enough to buffer a dry stretch. Avoid prolonged drought even in a mature row, because water stress increases susceptibility to Cytospora canker. Leaves emerge in spring, turn gold by fall and drop for a bare winter silhouette, so most of the water budget belongs to the warmer half of the year. WUCOLS rates it moderate water on the north-central coast, in the Central Valley, on the south coast and in South Inland. It rates high water in the high desert and the low desert.

In pots

Lombardy poplar can reach 40 to 70 feet, so plan a ground planting with space away from drains and paving. While a nursery tree remains potted, check the mix below the surface in California summer heat. Water through the drainage holes and empty any saucer afterward. Shelter the container from reflected heat. During its leafless winter period, check the mix before watering rather than keeping the pot constantly soaked.

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
1.22.43.64.90.4JAN0.65FEB1.09MAR1.52APR2.08MAY2.48JUN2.67JUL2.39AUG1.8SEP1.18OCT0.56NOV0.34DEC1.22.43.64.90.4JFM1.52AMJ2.67JAS1.18OND
Gallons per square foot per month, Central Valley. Peak 2.67 in Jul, 17.11 a year.

Monthly water need by climate zone

Lombardy Poplar: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.40.780.781.191.24
Feb0.530.650.810.871.491.49
Mar0.871.091.151.32.332.43
Apr1.181.521.41.613.033.12
May1.462.081.611.953.823.92
Jun1.612.481.742.294.564.46
Jul1.612.671.982.514.864.56
Aug1.492.391.862.334.464.17
Sep1.241.81.491.863.423.32
Oct0.871.181.151.332.332.38
Nov0.470.560.840.91.491.54
Dec0.310.340.650.681.041.09
Year1217.1115.518.4134.0333.73

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 Lombardy poplar. 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 Lombardy poplar 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 Lombardy poplar, 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 Lombardy poplar in summer?

In July, established Lombardy poplar 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 Lombardy poplar need per day?

In July in the Central Valley, established Lombardy poplar 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 Lombardy poplar change across California?

Yes. WUCOLS rates Lombardy poplar 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, high water in the High and Intermediate Desert zone, high water 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 Lombardy poplars short-lived?

They are especially prone to a canker disease that attacks the trunk and upper branches, often fatally. Stress from heat, drought or poor drainage can make a tree more vulnerable to infection. Consistent watering for its zone helps but does not remove the underlying disease risk.

What does Lombardy poplar foliage look like?

Its shiny green leaves are triangular to diamond-shaped. The foliage turns yellow in fall before the tree becomes bare.

Can I use Lombardy poplar as a privacy screen?

Yes, its fast growth and narrow form make it a traditional choice for quick screens and windbreaks. Because it is short-lived and canker-prone, plan for eventual gaps and replacement in the row. Give each tree enough root space to limit competition for water.

How do I stop Lombardy poplar suckers from spreading?

Remove unwanted shoots while they are small and keep checking the row for more. Suckering is part of this poplar's documented root habit.

Can Lombardy poplar roots damage pipes or pavement?

Its shallow, wide-spreading roots are a common cause of lifted paving and invaded irrigation lines close to the surface. Keep new plantings well away from foundations, walkways and sewer lines. Roots already established nearby will not retreat if watering changes.

Why does my Lombardy poplar look thin and sparse compared to when it was young?

Cytospora canker can kill branches on this poplar, and drought stress increases susceptibility. Inspect damaged wood and check soil moisture before deciding how to respond.

More plant watering guides

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Sources