WateringTimesWatering plan, $19
Populus x canadensis, WUCOLS IV

How often to water Carolina poplar in California

In July in the Central Valley, established Carolina poplar in loam needs a deep watering about every 5 days: about 55 gallons each time under a 10 foot canopy, about 76 gallons a week. Carolina poplar is a fast-growing hybrid of European black poplar and eastern cottonwood, with triangular, toothed leaves on an open, deciduous crown. It thrives along waterways with periodic flooding and rich soil, and it is a thirsty tree. Its aggressive roots and weak wood make where you plant it as important as how you water it.

TreeRated for 5 of 6 zones

How often to water Carolina 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 Carolina 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 6 inches down under the canopy in summer signals that a Carolina poplar needs a deep soak
  • Leaves yellowing and dropping early in summer heat point to drought stress in this thirsty tree
  • Holes in the trunk with sawdust or oozing sap point to borers, which go after stressed trees
  • Sunken, discolored patches on the bark or dying branches can signal canker disease
  • A soft, dark area at the trunk base warrants a check for crown rot, which a constantly wet trunk invites

How to water it

  • Water deeply and slowly over the wide root zone with drip or a soaker, keeping the trunk base dry
  • Soak the soil about 2 feet down, and water again before the upper few inches dry out in summer
  • Plant well away from buildings, paving and drain lines, since its aggressive roots can damage them
  • Mulch the root zone with wood chips to slow evaporation
  • Extend irrigation outward as the open crown spreads toward 40 feet

Through the seasons

A newly planted Carolina poplar needs deep, frequent soakings through its first summers while its roots spread. Established trees still use a great deal of water and need deep summer irrigation in most rated zones. It leafs out in spring, grows fast through summer and drops its leaves in fall. Rain covers the leafless months on the coast and in the Central Valley. WUCOLS rates Carolina poplar high water on the north-central coast, in the Central Valley, in the high desert and in the low desert. It rates moderate water in South Inland. WUCOLS has not evaluated it for the south coast.

In pots

Carolina poplar grows too fast and too large for a container beyond its first season. Keep a nursery tree in its pot only briefly, checking the mix daily in summer heat, since it dries out quickly. Water until it drains through, then empty the saucer. Plant it out in a spot well away from structures, pipes and paving. In winter, after leaf fall, water only when the mix begins to dry.

1 Your climate zone six WUCOLS zones, each from its own reference city
4.27gal per sq ft in JulyHigh water use in the Central Valley zone
A year
27.38 gal per sq ft
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses
1.22.43.64.90.64JAN1.04FEB1.74MAR2.43APR3.32MAY3.97JUN4.27JUL3.82AUG2.88SEP1.88OCT0.89NOV0.55DEC1.22.43.64.90.64JFM2.43AMJ4.27JAS1.88OND
Gallons per square foot per month, Central Valley. Peak 4.27 in Jul, 27.38 a year.

Monthly water need by climate zone

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

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.60.64–0.781.191.24
Feb0.841.04–0.871.491.49
Mar1.391.74–1.32.332.43
Apr1.882.43–1.613.033.12
May2.333.32–1.953.823.92
Jun2.583.97–2.294.564.46
Jul2.584.27–2.514.864.56
Aug2.383.82–2.334.464.17
Sep1.982.88–1.863.423.32
Oct1.391.88–1.332.332.38
Nov0.740.89–0.91.491.54
Dec0.50.55–0.681.041.09
Year19.227.38–18.4134.0333.73

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 high water in the Central Valley, like Carolina poplar. Plants that drink alike can share one valve and one schedule.

Big Leaf MapleAcer macrophyllumhigh water, Central Valley4.27 gal/sq ft in JulyWhite AlderAlnus rhombifoliahigh water, Central Valley4.27 gal/sq ft in JulyRed AlderAlnus rubra (Alnus oregona)high water, Central Valley4.27 gal/sq ft in JulyRiver BirchBetula nigrahigh water, Central Valley4.27 gal/sq ft in JulyWater BirchBetula occidentalishigh water, Central Valley4.27 gal/sq ft in JulyEuropean White BirchBetula pendulahigh water, Central Valley4.27 gal/sq ft in JulyWhite-Barked Himalayan BirchBetula utilis var. jacquemontiihigh water, Central Valley4.27 gal/sq ft in JulyEuropean BeechFagus sylvaticahigh water, Central Valley4.27 gal/sq ft in JulyBlack CottonwoodPopulus trichocarpa (Populus balsamifera)high water, Central Valley4.27 gal/sq ft in JulyWeeping WillowSalix babylonicahigh water, Central Valley4.27 gal/sq ft in JulyPeking WillowSalix matsudanahigh water, Central Valley4.27 gal/sq ft in JulyCoast RedwoodSequoia sempervirenshigh water, Central Valley4.27 gal/sq ft in JulyVine MapleAcer circinatumhigh water, Central Valley4.27 gal/sq ft in JulyHydrangeaHydrangea macrophylla & cvs.high water, Central Valley4.27 gal/sq ft in JulyBlueberriesVaccinium hybrids and cvs (CA native and non- native spp.)high water, Central Valley4.27 gal/sq ft in JulyShell GingerAlpinia zerumbethigh water, Central Valley4.27 gal/sq ft in July

Similar plants that need less water 16

Rated lower than Carolina poplar in the Central Valley. Worth a look for a new bed or a lawn replacement.

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
Minutes for your sprinklers

Turn this into minutes on your water days

Every city page has a calculator that takes Carolina 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 Carolina poplar in summer?

In July, established Carolina poplar in loam needs a deep watering about every 5 days in the Central Valley 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 Carolina poplar need per day?

In July in the Central Valley, established Carolina poplar needs about 11 gallons a day under a 10 foot canopy and about 43 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 Carolina poplar change across California?

Yes. WUCOLS rates Carolina poplar separately for each of the six California climate zones: high water in the North-Central Coastal zone, high water in the Central Valley zone, not evaluated 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.

Will Carolina poplar roots damage pipes?

Its aggressive root system makes it a poor choice near buildings, roads and drainage lines. Roots can lift paving and interfere with drains. Plant it well away from them.

Why do Carolina poplar branches break?

Its wood is weak, so limbs break in wind and storms. Fast growth on a tree this large adds to the risk. Keep it away from roofs and play areas, and remove damaged limbs promptly.

Does Carolina poplar cause allergies?

Its pollen is listed as an allergy hazard. Trees are either male or female, and the pollen comes from male trees.

Is Carolina poplar messy?

It drops seed fruit and twigs, and its leaves fall in autumn. Plan for cleanup under the crown, especially near patios.

Can Carolina poplar take wet soil?

Yes. It thrives where soils are rich and flood from time to time, like the riverbanks its parents come from. Even so, keep water off the trunk base, since crown rot is a known problem.

More plant watering guides

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Sources