WateringTimesWatering plan, $19
Magnolia grandiflora ssp. & cvs., WUCOLS IV

How often to water magnolia trees in California

In July in the Central Valley, established magnolia trees in loam need a deep watering about every 8 days: about 55 gallons each time under a 10 foot canopy, about 47 gallons a week. This guide follows southern magnolia, Magnolia grandiflora, with glossy evergreen leaves and fragrant flowers from late spring into summer. Its wide root system needs thorough watering and freely draining ground. Deciduous magnolias lose their leaves for winter and have different cool-season care.

TreeRated for 6 of 6 zones

How often to water magnolia trees, 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 magnolia trees 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

  • Drying soil a few inches beneath the mulch warrants a moisture check around southern magnolia's shallow roots before leaves show stress
  • Dull, drooping leaves with browning edges can accompany a dry root zone during summer heat
  • Older leaves can yellow and fall throughout the year, especially in spring, so leaf drop alone does not prove thirst
  • Yellow leaves over wet, sour-smelling soil can indicate poor drainage
  • Crown twig dieback over soggy ground warrants a root and drainage check before more irrigation

How to water it

  • Water beneath the magnolia canopy and a few feet beyond its branch tips, where the spreading roots extend
  • Use a ring of drip emitters or a slow hose so water soaks beneath the shallow roots
  • Soak magnolia roots about a foot deep or more, then recheck shallow moisture before it becomes dry
  • Keep wood-chip mulch across the root zone to protect shallow roots, leaving the trunk clear
  • Plant magnolia on a broad mound where drainage is poor, and expand emitters as roots spread without cultivating beneath the canopy

Through the seasons

Keep a new southern magnolia root ball evenly moist through its first summers, widening coverage as its fleshy roots spread. Established trees need long soakings over the expanding root area. They remain evergreen, shedding older leaves most heavily as spring growth arrives. Water matters from late spring through early fall during growth and flowering. Coastal and Central Valley rain can supply winter moisture; check both deserts through long dry gaps. WUCOLS rates southern magnolia moderate water on the north-central coast, in the Central Valley, on the south coast, in South Inland and in the high desert. It rates high water in the low desert.

In pots

Compact southern magnolias need large containers with clear drainage holes. Check the top two inches of mix often in summer, including daily checks during hot inland or desert weather. Water when dry there, soaking until excess leaves the holes, then empty the saucer. Protect the container from the hottest afternoon exposure. This evergreen keeps leaves in winter, so continue checks through dry spells while reducing irrigation as growth slows.

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
1.12.33.44.60.4JAN0.65FEB1.09MAR1.52APR2.08MAY2.48JUN2.67JUL2.39AUG1.8SEP1.18OCT0.56NOV0.34DEC1.12.33.44.60.4JFM1.52AMJ2.67JAS1.18OND
Gallons per square foot per month, Central Valley. Peak 2.67 in Jul, 17.11 a year.

Monthly water need by climate zone

Magnolia Trees: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.40.780.780.741.24
Feb0.530.650.810.870.931.49
Mar0.871.091.151.31.462.43
Apr1.181.521.41.611.893.12
May1.462.081.611.952.393.92
Jun1.612.481.742.292.854.46
Jul1.612.671.982.513.044.56
Aug1.492.391.862.332.794.17
Sep1.241.81.491.862.143.32
Oct0.871.181.151.331.462.38
Nov0.470.560.840.90.931.54
Dec0.310.340.650.680.651.09
Year1217.1115.518.4121.2733.73

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 magnolia trees. 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 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 JulyItalian AlderAlnus cordatamoderate water, Central Valley2.67 gal/sq ft in July

Similar plants that need less water 16

Rated lower than magnolia trees 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 magnolia trees, 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 magnolia trees in summer?

In July, established magnolia trees in loam need 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 do magnolia trees need per day?

In July in the Central Valley, established magnolia trees need 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 magnolia trees change across California?

Yes. WUCOLS rates magnolia trees 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, moderate 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.

How do I water a newly planted magnolia?

Probe the nursery root ball itself before relying on moisture in nearby ground. Soak when its upper soil starts drying, keeping it moist without saturation. Expand the wet area as roots move outward rather than waiting a fixed number of years.

Can lawn sprinklers water my magnolia?

Do not assume a lawn cycle reaches below the tree's surface roots. Check the depth it wets under the canopy. Give the magnolia its own slow emitters if turf watering leaves that soil dry.

How long should I run water on magnolia?

Avoid repeatedly digging through magnolia's fleshy surface roots. Use a narrow probe to check penetration and add emitters where the broad root area stays dry.

Why does my potted magnolia dry so quickly?

Check for a crowded, coiled root mass when a pot repeatedly dries fast. More container space may be needed as the tree grows. Use freely draining, bark-based mix and let water pass through to flush salts.

Why are my magnolia leaves yellow with green veins?

That pattern on the newest leaves can indicate iron chlorosis. High-pH soil and poor drainage can both contribute. Check soil conditions before treating the color as proof of thirst.

More plant watering guides

GrapevinesArborvitaeBambooCalla LiliesCannasClematisLilacsSpirea

Sources