WateringTimesWatering plan, $19
Agapanthus africanus, WUCOLS IV

How often to water lily of the Nile in California

In July in the Central Valley, established lily of the Nile in loam needs a deep watering about every 14 days: about 1.5 gallons each time for a plant 2 feet across, about 0.8 gallons a week. Lily of the Nile is an evergreen, clump-forming perennial from South Africa with strap-shaped leaves. In summer, erect stems up to about 2 1/2 feet carry round heads of deep blue, trumpet-shaped flowers. It takes most soils if they drain freely, and it flowers best when not allowed to dry out after blooming.

PerennialRated for 4 of 6 zones

How often to water lily of the Nile, month by month

Your city
Plant width
2 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 lily of the Nile 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 foot 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 2 to 3 inches down beside the clump in spring or summer signals lily of the Nile needs water
  • Leaves flopping and the flower stems wilting in heat can indicate thirst
  • Few flower stems the next summer can follow a dry spell in late summer after bloom
  • Yellowing, mushy leaf bases over cold, wet soil in winter suggest overwatering or poor drainage
  • Deformed, discolored buds that fail to open point to gall midge rather than a water problem

How to water it

  • Water around the clump with drip or a soaker, not over the flower heads
  • Soak about 8 inches down, then let the top inch or two dry before the next soak
  • Keep watering through late summer after flowering, since that sets next year's bloom
  • Plant in full sun in soil that drains freely, and cut back water in winter
  • Divide crowded clumps every few years in spring and replant at the same depth

Through the seasons

Water a new clump regularly through its first summer while roots settle. Established clumps want steady water from spring through flowering and into late summer, when next year's buds form. Plants grown as this species keep their leaves, so they need some moisture in every season. Cold, wet soil in winter is the main risk. WUCOLS rates lily of the Nile moderate water on the north-central coast, on the south coast and in South Inland. It carries a low water rating in the Central Valley. WUCOLS has not evaluated it for the high desert or the low desert.

In pots

Lily of the Nile is a classic container plant. Use moist but well-drained compost in full sun, and water through the growing season when the top inch dries. Let excess drain out and do not leave the pot in a full saucer. Keep watering after bloom so next year's flowers form. In winter, water much less and shelter the pot from hard frost. Divide a crowded pot in spring.

1 Your climate zone six WUCOLS zones, each from its own reference city
1.07gal per sq ft in JulyLow water use in the Central Valley zone
A year
6.84 gal per sq ft
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses
0.631.31.92.50.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.631.31.92.50.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

Lily of the Nile: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.160.780.78––
Feb0.530.260.810.87––
Mar0.870.431.151.3––
Apr1.180.611.41.61––
May1.460.831.611.95––
Jun1.610.991.742.29––
Jul1.611.071.982.51––
Aug1.490.951.862.33––
Sep1.240.721.491.86––
Oct0.870.471.151.33––
Nov0.470.220.840.9––
Dec0.310.140.650.68––
Year126.8415.518.41––

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 low water in the Central Valley, like lily of the Nile. Plants that drink alike can share one valve and one schedule.

AgapanthusAgapanthus orientalislow water, Central Valley1.07 gal/sq ft in JulyGeraniumsPelargonium x hortorum and cvs.low water, Central Valley1.07 gal/sq ft in JulySalviaSalvia greggii ssp., cvs. & hybridslow water, Central Valley1.07 gal/sq ft in JulyIrisesIris germanicalow water, Central Valley1.07 gal/sq ft in JulySucculentsEcheveria spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyRussian SagePerovskia spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyYarrowAchillea millefolium (non-native hybrids)low water, Central Valley1.07 gal/sq ft in JulyMountain AlyssumAlyssum montanumlow water, Central Valley1.07 gal/sq ft in JulySilver SageSalvia argentealow water, Central Valley1.07 gal/sq ft in JulyPurple MulleinVerbascum phoeniceumlow water, Central Valley1.07 gal/sq ft in JulySilvery YarrowAchillea clavennaelow water, Central Valley1.07 gal/sq ft in JulyFern Leaf YarrowAchillea filipendulinalow water, Central Valley1.07 gal/sq ft in JulyCalifornia Native YarrowAchillea millefolium (CA native cultivars)low water, Central Valley1.07 gal/sq ft in JulyWoolly YarrowAchillea tomentosalow water, Central Valley1.07 gal/sq ft in JulyPerennial HollyhockAlcea rosea cvs.low water, Central Valley1.07 gal/sq ft in JulyMountain Lady's MantleAlchemilla alpinalow 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 lily of the Nile, 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 lily of the Nile in summer?

In July, established lily of the Nile in loam needs a deep watering about every 14 days in the Central Valley, about every 7 days on the south coast and about every 6 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 lily of the Nile need per day?

In July in the Central Valley, established lily of the Nile needs about 0.1 gallons a day for a plant 2 feet across and about 0.4 gallons a day for a plant 4 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 lily of the Nile change across California?

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

Why is my agapanthus not blooming?

It is reluctant to flower if allowed to dry out after blooming in late summer. Keep watering through that period. It flowers in full sun, so heavy shade means fewer blooms.

Should I cut off agapanthus seed heads?

You do not have to, since the seed heads look attractive into winter. Cut stems back to the base once they fade. Removing them does not change its water needs.

When should I divide agapanthus?

Divide clumps every 3 to 4 years in spring. Water divisions well while they settle in.

What is damaging my agapanthus buds?

Agapanthus gall midge can deform buds so they fail to open. Remove affected flower heads. Slugs and snails can also chew leaves.

Is lily of the Nile evergreen?

Plants grown as this species are evergreen. Many other agapanthus lose their leaves in winter. Evergreen forms are more tender to cold.

More plant watering guides

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Sources