WateringTimesWatering plan, $19
Alnus glutinosa, WUCOLS IV

How often to water black alder in California

In July in the Central Valley, established black alder in loam needs a deep watering about every 8 days: about 55 gallons each time under a 10 foot canopy, about 47 gallons a week. Black alder is a deciduous tree with reddish brown catkins that open on bare branches in early spring before the leaves emerge. Its roots host nitrogen-fixing bacteria, which lets it grow in poor ground that would starve many other trees. It tolerates wet soil better than most landscape trees, so a dry summer stretch inland can stress it more than standing water would.

TreeRated for 4 of 6 zones

How often to water black alder, 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 black alder 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 alder with leaves drooping by midday over dry soil at the root ball needs a deep soak
  • Thin canopy and stunted shoots through a hot South Inland summer can point to a root zone that went too long without water
  • Branch tips dying back while the ground around the trunk stays saturated can indicate waterlogged roots
  • Suckers rising from the base or nearby soil reflect this tree's spreading habit rather than a watering issue

How to water it

  • Keep the planting site evenly moist, since this tree tolerates wet ground far better than most landscape trees
  • Water a newly planted alder across its root ball and the surrounding soil while its nitrogen-fixing nodules establish
  • Check soil moisture more often through a hot South Inland summer, where this tree carries a higher water rating
  • Use drip lines or a slow trickle so water soaks in rather than running off
  • Clear root suckers near the base by hand pruning instead of cutting back on irrigation to control them

Through the seasons

A newly planted black alder needs steady moisture while its roots establish and its nitrogen-fixing nodules develop. Established trees are deciduous, leafing out in spring after reddish brown catkins open on bare branches in early spring. This species tolerates wet soil better than most trees but still needs attention through a dry South Inland summer. Coastal and valley rain through the cool months typically keeps the root zone from drying out. WUCOLS rates black alder moderate water on the north-central coast, in the Central Valley and on the south coast. It rates high water in South Inland. WUCOLS marks it as not suited to the high desert or the low desert.

In pots

Black alder is usually grown in open ground rather than a container, since its spreading roots and eventual size suit it poorly to pot culture. A young tree can spend its first year or two in a large container while roots establish. Check the mix several inches down during California heat, since a pot dries faster than a planted bed. Let excess water run fully out the bottom, then tip out the saucer so the spreading roots do not sit wet. In winter, water only enough to keep the bare tree's roots from drying out completely, and plan to move it into the ground before roots crowd the pot.

1 Your climate zone six WUCOLS zones, each from its own reference city
2.67gal per sq ft in JulyModerate water use in the Central Valley zone
A year
17.11 gal per sq ft
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses
1.02.03.04.00.4JAN0.65FEB1.09MAR1.52APR2.08MAY2.48JUN2.67JUL2.39AUG1.8SEP1.18OCT0.56NOV0.34DEC1.02.03.04.00.4JFM1.52AMJ2.67JAS1.18OND
Gallons per square foot per month, Central Valley. Peak 2.67 in Jul, 17.11 a year.

Monthly water need by climate zone

Black Alder: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.40.781.24––
Feb0.530.650.811.39––
Mar0.871.091.152.08––
Apr1.181.521.42.58––
May1.462.081.613.12––
Jun1.612.481.743.67––
Jul1.612.671.984.02––
Aug1.492.391.863.72––
Sep1.241.81.492.98––
Oct0.871.181.152.13––
Nov0.470.560.841.44––
Dec0.310.340.651.09––
Year1217.1115.529.46––

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 moderate water in the Central Valley, like black alder. Plants that drink alike can share one valve and one schedule.

Citrus TreesCitrus spp.moderate water, Central Valley2.67 gal/sq ft in JulyJapanese MapleAcer palmatummoderate water, Central Valley2.67 gal/sq ft in JulyAvocado TreesPersea americanamoderate water, Central Valley2.67 gal/sq ft in JulyMagnolia TreesMagnolia grandiflora ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyPalm TreesSyagrus romanzoffiana (Arecastrum romanzoffianum)moderate water, Central Valley2.67 gal/sq ft in JulyApple TreesMalus spp. (edible) e.g, 'Anna' (low chill variety for low desert)moderate water, Central Valley2.67 gal/sq ft in JulyPeach TreesPrunus spp. ediblemoderate water, Central Valley2.67 gal/sq ft in JulyPersimmon TreesDiospyros kakimoderate water, Central Valley2.67 gal/sq ft in JulyAmur MapleAcer ginnalamoderate water, Central Valley2.67 gal/sq ft in JulyFernleaf MapleAcer japonicummoderate water, Central Valley2.67 gal/sq ft in JulyBox ElderAcer negundomoderate water, Central Valley2.67 gal/sq ft in JulyNorway MapleAcer platanoidesmoderate water, Central Valley2.67 gal/sq ft in JulyRed MapleAcer rubrummoderate water, Central Valley2.67 gal/sq ft in JulyChinese MapleAcer truncatummoderate water, Central Valley2.67 gal/sq ft in JulyRed BuckeyeAesculus paviamoderate water, Central Valley2.67 gal/sq ft in JulyRed HorsechestnutAesculus x carneamoderate water, Central Valley2.67 gal/sq ft in July

Similar plants that need less water 16

Rated lower than black alder in the Central Valley. Worth a look for a new bed or a lawn replacement.

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 black alder, 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 black alder in summer?

In July, established black alder in loam needs a deep watering about every 8 days in the Central Valley, about every 11 days on the south coast and about every 5 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 black alder need per day?

In July in the Central Valley, established black alder needs about 6.8 gallons a day under a 10 foot canopy and about 27 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 black alder change across California?

Yes. WUCOLS rates black alder separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, moderate water in the Central Valley zone, moderate water in the South Coastal zone, high 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.

Why does my black alder tolerate wet soil so well?

It is a wetland tree, found near ponds, lakes and rivers, and grows in moist to occasionally wet soil. Its roots also host nitrogen-fixing bacteria, which let it grow in poor soil. Good drainage still helps, but standing water is less of a threat than it is for most species.

Why are suckers coming up around the base of my alder?

This tree can send up root suckers that form dense thickets if left alone. Remove unwanted suckers at the base rather than adjusting irrigation. Repeated removal keeps the tree to a single trunk.

Does black alder need more water in hot inland areas?

Yes, WUCOLS rates it higher water in South Inland than on the coast or in the valley. A hot, dry summer stretch there can stress the tree more than it would near the coast. Check the root zone depth before assuming the tree is fine.

What causes the leaves on my alder to look chewed or spotted?

Alder lace bugs and leaf miners are common pests that mark the foliage without being tied to watering. Aphids can also cause curled or sticky leaves. Check for pests separately from checking soil moisture.

Can black alder grow in a low spot that collects water?

Yes, it tolerates short-term flooding better than most landscape trees. A spot that briefly holds water after rain suits it well. Avoid planting it where water never drains at all.

More plant watering guides

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Sources