WateringTimesWatering plan, $19
Azadirachta indica, WUCOLS IV

How often to water neem in California

In July on the north-central coast, established neem in loam needs a deep watering about every 13 days: about 55 gallons each time under a 10 foot canopy, about 29 gallons a week. Neem is a fast-growing evergreen tree from warm, semi-arid parts of Asia, grown in California mainly in mild, frost-free spots. It carries a deep taproot with wide lateral roots that reach moisture well below the surface once established. Under a prolonged dry spell, neem can drop much of its canopy rather than wilt outright.

TreeRated for 2 of 6 zones

How often to water neem, 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 neem 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

  • Ground that stays dry to the touch beyond a young neem's root spread calls for a soak
  • Leaflets folding or drooping during the heat of the day can indicate a thirsty young tree
  • Heavy, unseasonal leaf drop beyond normal thinning can point to prolonged dry soil
  • Yellowing leaves over constantly wet soil can indicate waterlogging, which neem tolerates poorly
  • Slowed new growth on an older tree in well-drained soil often reflects its naturally moderate needs rather than thirst

How to water it

  • Soak young neem trees across their whole root zone, expanding the wet circle as new roots spread out
  • Let the surface dry somewhat between soakings once the tree is established, since it favors well-drained ground
  • Use drip emitters or a slow soak rather than frequent shallow sprinkling
  • Choose a sandy or loamy, freely draining site, since standing water around the roots harms this tree quickly
  • Reduce watering frequency as the canopy matures and roots reach deeper, moist soil layers

Through the seasons

A young neem needs regular moisture while its taproot and lateral roots extend into the surrounding ground. Established trees are evergreen but can shed most of their leaves in a severe drought. Mature plants tolerate brief light frost, though a young tree is far more vulnerable to cold, so neem is planted mainly where California winters stay mild. WUCOLS rates neem moderate water on the north-central coast and on the south coast. WUCOLS has not evaluated it for the Central Valley, for South Inland, for the high desert or for the low desert. Coastal rain usually handles the cool months on its own, but check soil whenever a stretch passes without it.

In pots

A young neem tree can grow in a large container while it establishes, before planting out in a frost-free spot. Feel the mix a couple of inches down whenever California heat is intense, and water once that layer starts to dry. Let water pass fully out the bottom, then tip out the saucer so roots are not left sitting in it. Neem is sensitive to cold, so bring a potted tree under cover or indoors whenever frost threatens. Ease off watering in winter while growth slows and light and warmth are reduced.

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

WUCOLS lists Neem as not evaluated for the Central Valley zone, so no monthly figure is computed here.

Monthly water need by climate zone

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

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.37–0.78–––
Feb0.53–0.81–––
Mar0.87–1.15–––
Apr1.18–1.4–––
May1.46–1.61–––
Jun1.61–1.74–––
Jul1.61–1.98–––
Aug1.49–1.86–––
Sep1.24–1.49–––
Oct0.87–1.15–––
Nov0.47–0.84–––
Dec0.31–0.65–––
Year12–15.5–––

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 evaluated in the Central Valley, like neem. Plants that drink alike can share one valve and one schedule.

Hawthorn MapleAcer crataegifoliumnot rated, Central Valleyno Central Valley ratingMountain MapleAcer glabrumnot rated, Central Valleyno Central Valley ratingMiyabe MapleAcer miyabeinot rated, Central Valleyno Central Valley ratingEverglades PalmAcoelorraphe wrightiinot rated, Central Valleyno Central Valley ratingPink CedarAcrocarpus fraxinifoliusnot rated, Central Valleyno Central Valley ratingYellowwoodAfrocarpus falcatus (Podocarpus falcatus)not rated, Central Valleyno Central Valley ratingNew Caledonian PineAraucaria columnaris (A. cookii)not rated, Central Valleyno Central Valley ratingFormosa Sugar PalmArenga englerinot rated, Central Valleyno Central Valley ratingBismarck PalmBismarckia nobilisnot rated, Central Valleyno Central Valley ratingAmerican HornbeamCarpinus caroliniananot rated, Central Valleyno Central Valley ratingJapanese HornbeamCarpinus japonicanot rated, Central Valleyno Central Valley ratingAmerican YellowwoodCladrastis kentukeanot rated, Central Valleyno Central Valley ratingPagoda DogwoodCornus alternifolianot rated, Central Valleyno Central Valley ratingGiant DogwoodCornus controversanot rated, Central Valleyno Central Valley ratingButterfly PalmDypsis lutescens (Areca)not rated, Central Valleyno Central Valley ratingAbyssinian Coral TreeErythrina abyssinicanot 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 neem, 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 much water does neem need per day?

In July on the north-central coast, established neem needs about 4.1 gallons a day under a 10 foot canopy and about 16 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 neem change across California?

Yes. WUCOLS rates neem separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, not evaluated in the Central Valley zone, moderate water in the South Coastal zone, not evaluated in the South Inland zone, not evaluated in the High and Intermediate Desert zone, not evaluated in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

Can neem survive frost in California?

Cold snaps can damage or kill neem, so it is grown mainly in frost-free coastal spots. A young tree is especially vulnerable to a hard freeze. Move a potted neem under cover whenever frost is expected.

Why did my neem tree drop most of its leaves?

A prolonged dry spell can push neem to shed much of its canopy rather than wilt. Check soil moisture at depth before assuming a pest or disease problem.

Does neem need frequent watering once established?

Its deep taproot and wide lateral roots let an older tree draw on moisture well below the surface. Established trees tolerate drier soil between soakings than a young, shallow-rooted tree. Standing water around the base is a bigger risk than mild dryness.

Can I grow neem inland away from the coast?

Inland winters bring harder frosts than neem tolerates well. Extra heat also raises demand on a young tree's root system. A sheltered, frost-free spot improves its chances away from mild coastal air.

Why are my neem's leaves yellowing near the trunk?

Check whether the soil close to the trunk has stayed wet for an extended period. Constant dampness there favors root problems more than a nutrient issue. Letting that area dry between waterings often resolves early yellowing.

More plant watering guides

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Sources