WateringTimesWatering plan, $19
Carnegiea gigantea, WUCOLS IV

How often to water saguaro in California

In July on the south coast, established saguaro in loam needs a deep soak only about once a month or less: about 8.8 gallons each time for a plant 4 feet across. Saguaro is a slow growing columnar cactus with a ribbed, spiny trunk that can reach 40 feet over many decades. Most of its weight is stored water, so the pleated stem shrinks in drought and expands after a good soak. It belongs in hot, dry, sharply drained ground, and overwatering is a real threat because wet roots can rot.

ShrubCalifornia nativeRated for 3 of 6 zones

How often to water saguaro, month by month

Your city
Plant width
4 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 saguaro 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 the plant covers, 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 plant width

A shrub with its width marked from one side to the other and the circle under it shaded blue

Measure across the plant, from the tips of the leaves on one side to the tips on the other.

Water the whole area the plant covers, shown in blue. The gallons here cover that area.

A wider plant means more gallons each watering, not more waterings. While it is young, measure again each spring.

How to tell it needs water

  • A visibly shrunken stem with pleats drawn in tight during a long dry spell signals that a deep, infrequent soak would help
  • Soil dry several inches down across the wide, shallow root area after months without rain supports that cue
  • A fat, over-inflated look or vertical cracks in the troughs between pleats can indicate overwatering
  • Soft, dark, oozing patches on the stem point to bacterial rot, a common cause of saguaro death
  • Pale yellow bleaching on one side is sunburn, often after a change in orientation, not a sign of thirst

How to water it

  • Plant in sharply drained native soil with no organic amendments, at the same depth and compass direction it grew before
  • Wait several weeks after planting before the first watering, longer in cool weather, so damaged roots can dry and heal
  • Apply water slowly across the shallow, spreading root zone so it soaks in instead of running off
  • Give a planted saguaro occasional deep irrigation for at least four years while its root system forms
  • Keep lawn and other frequently watered plantings away from its root area

Through the seasons

A newly planted saguaro lives on its stored water for weeks while it regrows roots. Hold off at first, then give occasional deep soaks for several years. Established plants need help mainly during long droughts, and a stem that expands again shows the water was taken up. Saguaro is built for summer heat but sensitive to long, hard freezes, and freeze damage can take up to a year to prove fatal. In winter, keep its root zone on the dry side. WUCOLS rates saguaro very low water on the south coast and low water in South Inland and the low desert. WUCOLS marks it as not suited to the north-central coast, the Central Valley or the high desert.

In pots

A young saguaro can grow slowly in a container for years. Use a pot with large drainage holes and a gritty, fast draining cactus mix. In summer heat, check the mix every few days and water only when it is dry well below the surface. Let water drain freely, and never leave the pot standing in a saucer. Keep the same side facing the sun, since a rotated plant can sunburn on its newly exposed face. In winter, water very little and protect the pot from hard freezes.

1 Your climate zone six WUCOLS zones, each from its own reference city
Not ratedWUCOLS does not rate Saguaro for the Central Valley zone
A year
no figure
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses

WUCOLS lists Saguaro as not suited to this region for the Central Valley zone, so no monthly figure is computed here.

Monthly water need by climate zone

Saguaro: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan––0.080.31–0.31
Feb––0.080.35–0.37
Mar––0.110.52–0.61
Apr––0.140.64–0.78
May––0.160.78–0.98
Jun––0.170.92–1.12
Jul––0.21–1.14
Aug––0.190.93–1.04
Sep––0.150.74–0.83
Oct––0.110.53–0.6
Nov––0.080.36–0.38
Dec––0.070.27–0.27
Year––1.557.37–8.43

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 not suited to this region in the Central Valley, like saguaro. Plants that drink alike can share one valve and one schedule.

Chenille PlantAcalypha hispidanot rated, Central Valleyno Central Valley ratingCopperleafAcalypha wilkesiananot rated, Central Valleyno Central Valley ratingYellow Bell BauhiniaBauhinia tomentosanot rated, Central Valleyno Central Valley ratingMagic FlowerCantua buxifolianot rated, Central Valleyno Central Valley ratingClustered Fishtail PalmCaryota mitisnot rated, Central Valleyno Central Valley ratingHawaiian TiCordyline fruticosa (Cordyline terminalis)not rated, Central Valleyno Central Valley ratingFilbertCorylus maximanot rated, Central Valleyno Central Valley ratingPoinsettiaEuphorbia pulcherrimanot rated, Central Valleyno Central Valley ratingWeeping Chinese BanyanFicus benjaminanot rated, Central Valleyno Central Valley ratingRubber PlantFicus elasticanot rated, Central Valleyno Central Valley ratingFranklin TreeFranklinia alatamaha (Gordonia alatamaha)not rated, Central Valleyno Central Valley ratingJungle GeraniumIxora coccineanot rated, Central Valleyno Central Valley ratingOrange JessamineMurraya paniculatanot rated, Central Valleyno Central Valley ratingCommon GuavaPsidium guajavanot rated, Central Valleyno Central Valley ratingOrgan Pipe CactusStenocereus thurberi (Lemaireocereus thurberi)not rated, Central Valleyno Central Valley ratingGiant Bird of ParadiseStrelitzia nicolai (shade in desert)not rated, Central Valleyno Central Valley rating
Minutes for your sprinklers

Turn this into minutes on your water days

Every city page has a calculator that takes saguaro, 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 saguaro in summer?

In July, established saguaro in loam needs a deep watering about once a month or less 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 saguaro need per day?

In July on the south coast, established saguaro needs about 0.1 gallons a day for a plant 4 feet across and about 0.3 gallons a day for a plant 8 feet across. Give it in deep waterings spread days apart rather than a little every day, so the whole root zone gets wet.

Does watering for saguaro change across California?

Yes. WUCOLS rates saguaro separately for each of the six California climate zones: not suited to this region in the North-Central Coastal zone, not suited to this region in the Central Valley zone, very 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, 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.

How do I water a newly planted saguaro?

Leave it dry for several weeks after planting, longer in cool weather, so cut roots can heal. Then water deeply but occasionally while new roots form. It may shrink at first and visibly expand once those roots take up water.

Why is my saguaro splitting?

Vertical cracks in the troughs between pleats can follow overwatering, often with a fat, over-inflated look. Cut back irrigation and let the soil dry. Watch the cracks for soft, dark tissue, a sign of bacterial rot.

Can saguaro survive frost?

It handles brief cold, but freezes that stay below roughly 17 to 22 degrees F for 15 hours or more can be catastrophic. Cold sets the northern and upper elevation limits of its natural range. Survival also depends on the site's microclimate and the age of the plant.

Why is my saguaro turning yellow?

Pale yellow bleaching usually means sunburn, often after a plant is turned to face the sun differently. Keep a transplant in its original compass orientation. Severe burns brown and scar the skin and can let rot bacteria in.

Should I amend the soil when planting a saguaro?

No. Refill the hole firmly with native soil and skip organic amendments. Plant no deeper than it grew before, since a buried root hub gets too little of the rain that wets shallow soil.

When does a saguaro grow arms?

Arms usually begin only after the plant reaches about 8 feet tall, which takes many years. Extra water will not hurry this along and raises the risk of rot. Patience and sparse, deep soaks suit it best.

More plant watering guides

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Sources