WateringTimesWatering plan, $19
Acacia dealbata, WUCOLS IV

How often to water silver wattle in California

In July in the Central Valley, established silver wattle 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. Silver wattle is a fast-growing evergreen acacia from southeastern Australia with feathery gray-green leaves. Fluffy, fragrant yellow flower balls cover it from late winter into spring. Once established it needs very little water on the north-central coast and little in its other rated zones. It wants full sun, some shelter and soil that drains well.

TreeRated for 4 of 6 zones

How often to water silver wattle, 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 silver wattle 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

  • A young silver wattle is due for a soak when a trowel finds dry soil 4 to 6 inches down beside its root ball
  • Feathery leaves dropping heavily from a young tree in summer heat, over dry soil, can point to thirst
  • Yellowing foliage and a thinning crown over soggy soil point to poor drainage around the roots
  • Cottony white egg sacs along the twigs come from scale insects, not from a watering problem
  • Fine pale stippling and webbing on the leaves point to spider mites rather than dry soil

How to water it

  • Soak the root ball of a young tree and a ring of soil around it, tapering off once it is established
  • Soak deeply but seldom, letting the soil dry well down between waterings
  • Plant in full sun in neutral to acid soil that drains freely, in a spot sheltered from strong wind
  • Keep lawn sprinklers off the root zone of an established tree
  • Mulch with wood chips over the root zone, leaving the trunk clear

Through the seasons

Water a new silver wattle through its first summer or two, then taper off as it establishes. It grows quickly and blooms from late winter into early spring, when yellow puffballs cover the crown, followed by bean-like pods. Established trees rely mostly on winter rain on the coast and in the valley, with occasional deep summer soakings inland. On the north-central coast WUCOLS rates silver wattle very low water. The Central Valley, the south coast and South Inland rate low water. WUCOLS marks the low desert and the high desert as not suited for it.

In pots

Silver wattle can spend a few years in a large patio container while it is young. Use a gritty, free-draining mix. In summer, probe 2 to 3 inches into the mix every few days and water once it feels dry at that depth. Water until it drains, then empty the saucer so the roots never sit wet. This fast grower soon fills a pot, so plan to plant it out. In winter, rain may be enough, so water only when the mix is dry below the surface.

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
0.270.540.801.10.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.270.540.801.10.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

Silver Wattle: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.040.160.310.31––
Feb0.050.260.320.35––
Mar0.090.430.460.52––
Apr0.120.610.560.64––
May0.150.830.640.78––
Jun0.160.990.690.92––
Jul0.161.070.791––
Aug0.150.950.740.93––
Sep0.120.720.60.74––
Oct0.090.470.460.53––
Nov0.050.220.330.36––
Dec0.030.140.260.27––
Year1.26.846.27.37––

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 silver wattle. 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 JulyGreen WattleAcacia decurrenslow water, Central Valley1.07 gal/sq ft in JulySydney Golden WattleAcacia longifolialow water, Central Valley1.07 gal/sq ft in JulyBlackwood AcaciaAcacia melanoxylonlow 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 silver wattle, 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 silver wattle in summer?

In July, established silver wattle 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 silver wattle need per day?

In July in the Central Valley, established silver wattle 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 silver wattle change across California?

Yes. WUCOLS rates silver wattle separately for each of the six California climate zones: very 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, not suited to this region in the High and Intermediate Desert zone, not suited to this region in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

When does silver wattle bloom?

From late winter into early spring, with fragrant yellow flower balls in clusters. A sunny, sheltered site gives the best show. Bloom does not call for extra water in a normal wet winter.

Should I prune silver wattle hard?

No. It resents hard pruning, so shape it lightly and only when needed. Plant it where it has room to grow instead.

How fast does silver wattle grow?

Fast. It can reach 40 to 50 feet tall and wide in time. Give it space away from buildings, and plan drip lines that can follow its spread.

Is silver wattle the same as mimosa?

Its cut flowers are sold as mimosa, but the tree is an acacia. It is a different tree from silk tree, which also goes by mimosa.

What pests attack silver wattle?

Watch for scale, mealybugs and spider mites. Check twigs and leaf undersides in summer. Watering changes will not clear them.

More plant watering guides

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Sources