WateringTimesWatering plan, $19
Casuarina cunninghamiana, WUCOLS IV

How often to water river she-oak in California

In July in the Central Valley, established river she-oak 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 she-oak is a fast-growing evergreen tree from eastern Australia that reaches 50 to 60 feet tall. Its long, needlelike, grayish green twigs carry tiny scalelike leaves. Small reddish brown flowers in spring give way to little conelike fruits. It takes most soils, accepts periodic flooding and needs little water once established near the coast.

TreeRated for 6 of 6 zones

How often to water river she-oak, 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 she-oak 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

  • Needlelike twigs on river she-oak thinning or browning while the soil is dry deep down mean it needs a soak
  • Steady twig drop on a young tree in dry soil means its roots need a deep drink
  • Seedlings popping up around the tree show it is self-sowing, not that it needs more water
  • Root suckers forming a thicket are normal for this tree and need pulling

How to water it

  • Water a young tree deeply at the root zone, then let the soil dry between soaks
  • Plant in full sun in almost any soil, including spots that flood now and then
  • Give deeper summer soaks in the high desert and the low desert
  • Pull seedlings and suckers before they form thickets
  • Think twice about planting it near wild land in southern California, where it may spread

Through the seasons

Water a new tree regularly through its first summers while roots spread. Established trees near the coast and in the Central Valley need little water, and winter rain covers the cool months there. In desert heat, summer calls for regular deep soaks. It is evergreen and flowers in spring. WUCOLS rates river she-oak low water on the north-central coast, in the Central Valley, on the south coast and in South Inland. It needs more in the deserts, where WUCOLS rates river she-oak moderate water in the high desert and in the low desert.

In pots

River she-oak grows too large and too fast to stay in a pot for long. A young tree can wait in a deep container until planting time. Fill it with a well-drained mix. Soak it once the upper two inches feel dry, and let the excess run off. Through summer, look at it every other day. Empty the saucer after each watering. Plant it out early, before roots circle. Through the rainy months, add water only if the mix goes dry.

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 She-Oak: 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 she-oak. 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 she-oak, 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 she-oak in summer?

In July, established river she-oak 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 she-oak need per day?

In July in the Central Valley, established river she-oak 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 she-oak change across California?

Yes. WUCOLS rates river she-oak 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.

Is river she-oak invasive?

It self-sows heavily and spreads by suckers into thickets. It may be invasive in coastal southern California. Remove seedlings promptly.

Is river she-oak a pine?

No, its needles are really slender green twigs. The true leaves are tiny scales along them. The small cones are its fruit.

Can river she-oak handle wet soil?

Yes, it accepts periodic flooding. It also grows in most soils. That makes it useful along streams and low spots.

How fast does river she-oak grow?

It grows fast to 50 to 60 feet tall and 25 to 30 feet wide. Give it plenty of room. It is too big for small lots.

Is river she-oak the same as Casuarina equisetifolia?

No, but it is sometimes sold under that name. That species is less hardy to cold and more tolerant of salt spray. Check the botanical name before buying.

More plant watering guides

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Sources