WateringTimesWatering plan, $19
Vachellia farnesiana (Acacia farnesiana), WUCOLS IV

How often to water sweet acacia in California

In July in the Central Valley, established sweet acacia 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. Sweet acacia is a thorny, semi-evergreen shrub or small tree, usually multi-trunked, with feathery light green leaves. Fragrant puffballs of bright yellow flowers cover it in spring, followed by dark purplish red pods. It needs full sun and well drained soil, and once established it gets by on little water.

TreeRated for 5 of 6 zones

How often to water sweet acacia, 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 sweet acacia 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 sweet acacia is due for a soak when the soil 4 inches down beside its root ball has dried
  • Leaflets yellowing and dropping during a long summer dry spell can mean a young plant is thirsty
  • Wilting branches and dark, gummy bark at the soil line over wet ground point to Phytophthora root and crown rot
  • White, cottony egg sacs on the twigs are cottony cushion scale, a common acacia pest rather than a water problem
  • Some leaf drop in a cold winter is normal for this semi-evergreen plant

How to water it

  • Give deep, infrequent soakings, letting the soil dry well between them
  • Plant in full sun in soil that drains freely, never in a low, wet spot
  • Water a young plant at the root ball and just beyond it, then taper off as it establishes
  • Keep emitters and sprinkler spray off the trunks so the crown stays dry
  • Lay irrigation lines before planting, since the thorny branches make later work difficult

Through the seasons

Water a new sweet acacia regularly through its first summer, then switch to deep soakings spaced well apart. Fragrant yellow flowers open in spring, and dark pods follow. It is semi-evergreen and may shed leaves in a cold winter. Winter rain usually covers the cool months on the coast and in the valley, while low desert plants may need an occasional winter soak. WUCOLS rates sweet acacia very low water on the north-central coast and in South Inland. It rates low water in the Central Valley, on the south coast and in the low desert. WUCOLS marks it as not suited to the high desert.

In pots

Sweet acacia can grow in a large container for a few years, which suits a sunny patio. Use a gritty, fast-draining mix. Check the mix 2 to 3 inches down every few days in summer heat, and water deeply once it is dry there. Let the excess run out, then empty the saucer. Its spines make it a poor choice beside seating, so place the pot with care. In winter, water sparingly, since wet mix invites root rot.

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
0.280.570.851.10.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.280.570.851.10.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

Sweet Acacia: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.040.160.310.08–0.31
Feb0.050.260.320.09–0.37
Mar0.090.430.460.13–0.61
Apr0.120.610.560.16–0.78
May0.150.830.640.2–0.98
Jun0.160.990.690.23–1.12
Jul0.161.070.790.25–1.14
Aug0.150.950.740.23–1.04
Sep0.120.720.60.19–0.83
Oct0.090.470.460.13–0.6
Nov0.050.220.330.09–0.38
Dec0.030.140.260.07–0.27
Year1.26.846.21.84–8.43

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 sweet acacia. 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 sweet acacia, 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 sweet acacia in summer?

In July, established sweet acacia in loam needs a deep watering about every 20 days in the Central Valley, about every 27 days on the south coast and about once a month or less 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 sweet acacia need per day?

In July in the Central Valley, established sweet acacia 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 sweet acacia change across California?

Yes. WUCOLS rates sweet acacia 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, very low water in the South Inland zone, not suited to this region in the High and Intermediate Desert zone, low 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 sweet acacia invasive?

It can form thickets and become weedy. Pull seedlings that sprout under it, and pick up pods if its spread is a concern.

Does sweet acacia have thorns?

Yes. Its branches carry substantial spines, so plant it away from paths and play areas. Wear gloves when you prune it.

When does sweet acacia bloom?

In spring, with fragrant, bright yellow puffball flowers. Dark purplish red pods follow the bloom.

What pests attack sweet acacia?

Cottony cushion scale, other scales and psyllids are common on acacias. Check the twigs for white egg sacs or sticky honeydew. Watering will not clear them.

Is sweet acacia the same as Acacia farnesiana?

Yes. Botanists moved it to Vachellia farnesiana, but nurseries may still sell it as Acacia farnesiana or Vachellia constricta.

More plant watering guides

CoralberryPurple MulleinBailey AcaciaSilver WattleGreen WattleSydney Golden WattleBlackwood AcaciaBlue Leaf Wattle

Sources