WateringTimesWatering plan, $19
Catalpa speciosa, WUCOLS IV

How often to water western catalpa in California

In July in the Central Valley, established western catalpa 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. Western catalpa is a deciduous tree from the central United States, 40 to 70 feet tall, with huge heart-shaped leaves and a rounded crown. In late spring it carries showy spikes of ruffled white flowers marked yellow and purple, then long, narrow seedpods. It is adaptable to most soils and takes seasonal flooding, though dropping flowers, leaves and pods can be messy.

TreeRated for 6 of 6 zones

How often to water western catalpa, 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 western catalpa 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

  • Soil dry a foot down under the canopy in summer signals a young western catalpa needs a deep soak
  • Large leaves wilting through the afternoon can indicate a dry root zone
  • Leaves scorching brown at the edges in hot wind can follow dry soil
  • Yellowing leaves over soil that stays soggy for weeks suggest drainage trouble

How to water it

  • Water in a wide ring under the canopy and past its edge with soakers
  • Soak 18 inches deep, then let the top few inches dry before the next soak
  • Plant in full sun or part shade in almost any soil
  • Site it away from patios and pools where flowers, leaves and pods drop
  • Shift emitters outward as the large crown grows

Through the seasons

Water a young catalpa deeply through its first summers. Established trees are adaptable and take seasonal flooding, but they benefit from deep soaks in long, hot summers. It is deciduous, with yellow fall leaves that drop and darken. Flowers come in late spring, before the southern catalpa. WUCOLS rates western catalpa low water on the north-central coast. The Central Valley, the south coast and South Inland carry a moderate water rating, and so do the high desert and the low desert.

In pots

Western catalpa grows into a big tree and only suits a container while young. A sapling can spend a season in a deep pot of well-drained mix. Water when the top couple of inches dry, until water runs out the bottom. In summer, its large leaves can dry a pot within a day or two. Empty the saucer. After leaf drop, water lightly and plant it out before roots circle 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
0.761.52.33.00.4JAN0.65FEB1.09MAR1.52APR2.08MAY2.48JUN2.67JUL2.39AUG1.8SEP1.18OCT0.56NOV0.34DEC0.761.52.33.00.4JFM1.52AMJ2.67JAS1.18OND
Gallons per square foot per month, Central Valley. Peak 2.67 in Jul, 17.11 a year.

Monthly water need by climate zone

Western Catalpa: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.150.40.780.780.740.78
Feb0.210.650.810.870.930.93
Mar0.351.091.151.31.461.52
Apr0.471.521.41.611.891.95
May0.582.081.611.952.392.45
Jun0.642.481.742.292.852.79
Jul0.642.671.982.513.042.85
Aug0.62.391.862.332.792.6
Sep0.51.81.491.862.142.08
Oct0.351.181.151.331.461.49
Nov0.190.560.840.90.930.96
Dec0.120.340.650.680.650.68
Year4.817.1115.518.4121.2721.08

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 western catalpa. 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 western catalpa 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 western catalpa, 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 western catalpa in summer?

In July, established western catalpa 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 9 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 western catalpa need per day?

In July in the Central Valley, established western catalpa 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 western catalpa change across California?

Yes. WUCOLS rates western catalpa separately for each of the six California climate zones: low water in the North-Central Coastal zone, moderate water in the Central Valley zone, moderate water in the South Coastal zone, moderate water in the South Inland zone, moderate water in the High and Intermediate Desert zone, moderate 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 western catalpa messy?

Yes, dropping flowers, large leaves and long seedpods make cleanup a chore. Plant it away from patios, pools and walkways. The show in bloom is worth it in the right spot.

What are the caterpillars on my catalpa?

They are likely catalpa sphinx caterpillars, a native moth that feeds on the leaves. Birds eat them.

How is western catalpa different from southern catalpa?

Western catalpa is hardier and blooms earlier. Southern catalpa leaves have a stronger odor. Both have showy white flowers.

Can western catalpa grow in wet soil?

It accepts seasonal flooding and grows in most soils. Constantly waterlogged ground is still best avoided. Drainage helps the roots.

Is catalpa wood strong?

The wood is brittle, and limbs can break in storms. Prune young trees to a strong structure. Keep it away from roofs and power lines.

More plant watering guides

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Sources