WateringTimesWatering plan, $19
Amorpha fruticosa, WUCOLS IV

How often to water false indigo bush in California

In July on the south coast, established false indigo bush in loam needs a deep watering about every 11 days: about 8.8 gallons each time for a plant 4 feet across, about 5.6 gallons a week. False indigo bush is a deciduous native shrub of the pea family, 3 to 12 feet tall, with fine, aromatic leaves. In spring and early summer it carries narrow spikes of tiny purple flowers with bright orange or yellow anthers. In southern California it grows on sheltered north slopes, in canyon bottoms and along streams, in soil that stays slightly moist but not wet.

ShrubCalifornia nativeRated for 3 of 6 zones

How often to water false indigo bush, 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 false indigo bush 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

  • Soil dry 3 inches down around false indigo bush in summer signals that it needs a deep soak, since it grows in moist spots
  • Leaves yellowing and dropping early on a hot, sunny slope point to a site that is too hot and dry for it
  • Leaves spotting and stems dying back in soil that stays soggy can point to too much water
  • Leaves chewed by small caterpillars may be dogface butterfly larvae, which feed on this plant, rather than a sign of stress
  • A white powdery coating on the leaves points to powdery mildew rather than thirst

How to water it

  • Water at the base of the shrub with drip or a soaker, wetting the root zone about 18 inches deep
  • Let the top few inches dry between soakings, keeping the soil slightly moist rather than wet
  • Plant it in a cool, part-shaded spot, such as a north slope, a canyon edge or the side of a stream
  • Mulch with leaf litter to keep the soil cool and evenly moist
  • Water a ring wide enough for the thicket it may form, and pull seedlings where you do not want them

Through the seasons

A new false indigo bush needs steady moisture through its first summer while its roots settle. Established shrubs still want summer water, especially on warm sites, since they grow wild where the soil stays slightly moist. Flowers come in spring and early summer, and the shrub drops its leaves in fall. Winter rain usually covers its dormant months on the south coast. WUCOLS rates false indigo bush moderate water on the south coast and in the high desert. It rates low water in South Inland. WUCOLS has not evaluated it for the north-central coast, the Central Valley or the low desert.

In pots

False indigo bush is a large, fast shrub, so a pot suits it only while it is young. Use a large container with a loamy mix and check it 2 inches down every few days in summer, watering when it begins to dry. Let the excess drain and empty the saucer, since the roots like moisture without standing water. Keep the pot in afternoon shade. After the leaves drop in fall, water lightly only when the mix dries.

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

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

Monthly water need by climate zone

False Indigo Bush: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan––0.780.310.74–
Feb––0.810.350.93–
Mar––1.150.521.46–
Apr––1.40.641.89–
May––1.610.782.39–
Jun––1.740.922.85–
Jul––1.9813.04–
Aug––1.860.932.79–
Sep––1.490.742.14–
Oct––1.150.531.46–
Nov––0.840.360.93–
Dec––0.650.270.65–
Year––15.57.3721.27–

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 false indigo bush. Plants that drink alike can share one valve and one schedule.

Formosa Sugar PalmArenga englerinot rated, Central Valleyno Central Valley ratingChilean Feather BambooChusquea culeou (C. breviglumis)not rated, Central Valleyno Central Valley ratingBlackbrushColeogyne ramosissimanot rated, Central Valleyno Central Valley ratingGlaucous Scorpion VetchCoronilla valentina glaucanot rated, Central Valleyno Central Valley ratingWillowleaf CotoneasterCotoneaster salicifoliusnot rated, Central Valleyno Central Valley ratingMadagascar SagoCycas thouarsii (SHADE)not rated, Central Valleyno Central Valley ratingIrish HeathDaboecia cantabricanot rated, Central Valleyno Central Valley ratingButterfly PalmDypsis lutescens (Areca)not rated, Central Valleyno Central Valley ratingUmbrella BambooFargesia murielaenot rated, Central Valleyno Central Valley ratingBlue Fountain BambooFargesia nitida (Sinarundinaria nitida) (BAMBOO)not rated, Central Valleyno Central Valley ratingPrickly HeathGaultheria mucronata (Pernettya mucronata)not rated, Central Valleyno Central Valley ratingOtterbossieGossypium harknessiinot rated, Central Valleyno Central Valley ratingBox-leaved HollyIlex crenatanot rated, Central Valleyno Central Valley ratingBellyache BushJatropha gossypiifolianot rated, Central Valleyno Central Valley ratingMountain LaurelKalmia latifolianot rated, Central Valleyno Central Valley ratingBarbados CherryMalpighia glabranot 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 false indigo bush, 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 false indigo bush in summer?

In July, established false indigo bush in loam needs a deep watering about every 11 days 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 false indigo bush need per day?

In July on the south coast, established false indigo bush needs about 0.8 gallons a day for a plant 4 feet across and about 3.2 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 false indigo bush change across California?

Yes. WUCOLS rates false indigo bush separately for each of the six California climate zones: not evaluated in the North-Central Coastal zone, not evaluated in the Central Valley zone, moderate water in the South Coastal zone, low water in the South Inland zone, moderate water 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.

Is false indigo bush native to California?

Yes. Wild plants turn up in San Diego and western Riverside counties, mostly in cool, sheltered, moist places, and the species ranges east to the Atlantic. It suits a native butterfly garden.

Why are caterpillars eating my false indigo?

It is a host plant for the California dogface and southern dogface butterflies, as well as skippers and hairstreaks. Some leaf feeding is the price of hosting them. Check the soil separately before deciding to water.

Can false indigo bush take full sun?

It grows in full sun to part shade, but in California it prefers cool, sheltered spots. It is not found on hot south-facing slopes, so give it afternoon shade inland.

Does false indigo bush spread?

It self-sows and can form thickets in moist spots. Pull unwanted seedlings while they are small, or let it fill in along a stream bank or drainage swale.

What do false indigo flowers look like?

Each tiny flower has a single purple petal around bright yellow or orange anthers, packed into narrow spikes. They open in spring and early summer and draw bees and butterflies.

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Sources