WateringTimesWatering plan, $19
Eucalyptus camaldulensis, WUCOLS IV

How often to water river red gum in California

In July in the Central Valley, established river red gum 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. River red gum is a fast-growing Australian eucalyptus that can reach 65 to 90 feet. Its peeling bark is creamy white, and its narrow leaves are gray-green. In its native range it grows along streambanks and on land that floods seasonally. That riverside origin shows in California, where drought-stressed trees suffer more from lerp psyllids and borers.

TreeRated for 6 of 6 zones

How often to water river red gum, 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 river red gum 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 beneath the outer canopy of a young red gum signals that it needs a deep soak
  • Sticky honeydew, black sooty mold and tiny white caps on the leaves mark redgum lerp psyllid, which hits drought-stressed trees hardest
  • Heavy leaf drop in summer and fall can follow psyllid feeding or dry soil, so check both before watering
  • Holes in the bark with stains or oozing on the trunk point to longhorned borers, which go after water-stressed trees
  • A soggy root crown with honey-colored mushrooms at the trunk base warns of root rot from waterlogged soil

How to water it

  • Apply water beneath the outer canopy, not near the trunk, with drip emitters or a slow soaker
  • Soak the soil a foot or more deep in one long, slow session rather than in frequent light sprinklings
  • Keep lawn sprinklers off the root crown, since shallow turf watering never reaches the deep roots
  • Keep nitrogen fertilizer away from the root zone, since it pushes the soft new leaves that psyllids favor
  • Move emitters outward as the canopy spreads so the wet zone stays under the outer branches

Through the seasons

A young river red gum needs deep soakings through its first two or three summers while roots spread. Established trees get by on less, but this streambank species stresses during long summer and fall drought, so give occasional deep soakings then. It stays evergreen and flowers from late spring to midsummer. Winter rain covers the cool months on the coast and in the Central Valley. In four zones, the north-central coast, the Central Valley, the south coast and South Inland, WUCOLS rates river red gum low water. The high desert and the low desert both carry a moderate water rating.

In pots

River red gum is a large, fast tree that does not belong in a pot for long. A nursery seedling can wait a season in a deep container before planting. Check the mix 2 to 3 inches down every few days in summer. Soak it until water runs out the bottom, then empty the saucer. Plant it out before the roots start circling the pot. A cramped, dry container invites the same stress that draws psyllids to trees in the ground.

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
0.761.52.33.00.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.761.52.33.00.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

River Red Gum: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.150.160.310.310.740.78
Feb0.210.260.320.350.930.93
Mar0.350.430.460.521.461.52
Apr0.470.610.560.641.891.95
May0.580.830.640.782.392.45
Jun0.640.990.690.922.852.79
Jul0.641.070.7913.042.85
Aug0.60.950.740.932.792.6
Sep0.50.720.60.742.142.08
Oct0.350.470.460.531.461.49
Nov0.190.220.330.360.930.96
Dec0.120.140.260.270.650.68
Year4.86.846.27.3721.2721.08

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 river red gum. 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 river red gum, 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 river red gum in summer?

In July, established river red gum in loam needs a deep watering about every 20 days in the Central Valley, about every 27 days on the south coast and about every 22 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 river red gum need per day?

In July in the Central Valley, established river red gum 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 river red gum change across California?

Yes. WUCOLS rates river red gum separately for each of the six California climate zones: low water in the North-Central Coastal zone, low water in the Central Valley zone, low water in the South Coastal zone, low water in the South Inland zone, moderate water in the High and Intermediate Desert zone, moderate 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 is my red gum dripping something sticky?

The sticky drip is often honeydew from redgum lerp psyllids, which favor this species. Black sooty mold grows on it, and heavy infestations drop leaves early. Deep watering during drought reduces the stress that lets psyllids build up.

Do borers kill river red gum?

Eucalyptus longhorned borers attack stressed trees, and river red gum is among the more resistant species. A tree left dry through a long drought can still become a target. Holes and oozing on the trunk call for deep watering and a closer inspection.

Should I water a mature red gum in a lawn?

Frequent shallow lawn watering does not reach the deep roots and keeps the root crown wet. Give the tree its own deep soakings under the outer canopy during long dry spells instead. Keep turf back from the trunk.

Is river red gum invasive?

It can spread invasively, especially along streams and in other riparian habitats. Avoid planting it near creeks or wild wetlands. Shedding bark and falling seed capsules also make it messy near paving.

How big does river red gum get?

It grows fast to 65 to 90 feet tall and 40 to 65 feet wide. Give it open ground with room for that spread. Plan its watering zone around the mature canopy, not the young tree.

More plant watering guides

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Sources