WateringTimesWatering plan, $19
Plumbago auriculata (capensis) ssp. & cvs., WUCOLS IV

How often to water cape plumbago in California

In July in the Central Valley, established cape plumbago in loam needs a deep watering about every 8 days: about 8.8 gallons each time for a plant 4 feet across, about 7.6 gallons a week. Cape plumbago is an evergreen South African shrub whose long, arching stems mound 5 to 8 feet tall and wide. Clusters of sky-blue or white flowers appear from spring through fall and, in mild spots, almost all year. It needs sun or part shade and soil that drains, and its sap can severely irritate skin.

ShrubRated for 6 of 6 zones

How often to water cape plumbago, 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 cape plumbago 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 several inches down around the mound in summer heat means it is ready for a deep soak
  • Fewer flowers in a shady spot reflect too little sun, not too little water
  • Yellowing leaves over soil that stays wet point to poor drainage rather than thirst
  • Leaves damaged after nights below about 25 degrees F reflect cold, not drought, and the roots usually survive
  • Sticky seed pods catching on clothing are its normal fruit, not a sign of stress

How to water it

  • Run drip at the base of the mound long enough to soak roughly 12 inches deep
  • Allow the upper soil to dry out between soakings, since established plants look best with only occasional irrigation
  • Plant in sun or part shade in well-drained soil, away from paths where the sticky fruit catches clothing
  • Cut back in late winter, when bloom is lightest, to renew the plant and control its size
  • Tie long stems to a support if you want it to climb, and widen watering as rooting stems spread

Through the seasons

Water new plants regularly through their first summer. Established plants bloom from spring through fall and flower on the current year's growth, so a late winter cutback brings fresh flowering stems. Winter is its slowest season, and it needs little water then. Hard frost can knock back the top growth. On the north-central coast, WUCOLS rates cape plumbago low water. The Central Valley, the south coast and South Inland carry a moderate water rating. Both desert zones, the high desert and the low desert, share that moderate water rating.

In pots

Cape plumbago makes a good container specimen, and a pot can move under cover where winters get cold. Use a well-drained mix and a large pot with drainage holes. During hot weather, push a finger into the mix every other day and water once it is dry to the second knuckle. Let the water drain through, then empty the saucer. Cut it back in late winter. Through the cool months, water sparingly.

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

Cape Plumbago: 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 cape plumbago. Plants that drink alike can share one valve and one schedule.

RosesRosa hybrids..bushmoderate water, Central Valley2.67 gal/sq ft in JulyAzaleasRhododendron spp. (CA native and non-native spp.)moderate water, Central Valley2.67 gal/sq ft in JulyCamelliasCamellia japonica (SHADE IN DESERT)moderate water, Central Valley2.67 gal/sq ft in JulyGardeniasGardenia spp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyBird of ParadiseStrelitzia reginae (shade in desert)moderate water, Central Valley2.67 gal/sq ft in JulyHibiscusHibiscus rosa-sinensismoderate water, Central Valley2.67 gal/sq ft in JulySago PalmCycas revolutamoderate water, Central Valley2.67 gal/sq ft in JulyStar JasmineTrachelospermum jasminoides and cvs.moderate water, Central Valley2.67 gal/sq ft in JulyArborvitaeThuja occidentalis ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyBambooBambusa spp.moderate water, Central Valley2.67 gal/sq ft in JulyLilacsSyringa hybrids (including Descanso hybrids)moderate water, Central Valley2.67 gal/sq ft in JulySpireaSpiraea spp. (CA native and non native spp.)moderate water, Central Valley2.67 gal/sq ft in JulyButterfly BushBuddleja davidii and hybridsmoderate water, Central Valley2.67 gal/sq ft in JulySageSalvia officinalis and cvs.moderate water, Central Valley2.67 gal/sq ft in JulyRed BuckeyeAesculus paviamoderate water, Central Valley2.67 gal/sq ft in JulyWestern ServiceberryAmelanchier alnifoliamoderate water, Central Valley2.67 gal/sq ft in July

Similar plants that need less water 16

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

LavenderLavandula spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyRosemaryRosmarinus officinalislow water, Central Valley1.07 gal/sq ft in JulyBougainvilleaBougainvillea & spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyOlive TreesOlea europaea 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 JulyLantanaLantana camara ssp. & cvs.low water, Central Valley1.07 gal/sq ft in JulySalviaSalvia greggii ssp., cvs. & hybridslow water, Central Valley1.07 gal/sq ft in JulyAloeAloe spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulySucculentsEcheveria spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyJunipersJuniperus spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyRussian SagePerovskia spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulySagebrushArtemisia spp. (shrubby)low water, Central Valley1.07 gal/sq ft in JulyWild PrivetLigustrum vulgarelow water, Central Valley1.07 gal/sq ft in JulyCoralberrySymphoricarpos orbiculatus (SHADE)low water, Central Valley1.07 gal/sq ft in JulySydney Golden WattleAcacia longifolialow water, Central Valley1.07 gal/sq ft in JulyBlue Leaf WattleAcacia salignalow 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 cape plumbago, 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 cape plumbago in summer?

In July, established cape plumbago 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 cape plumbago need per day?

In July in the Central Valley, established cape plumbago needs about 1.1 gallons a day for a plant 4 feet across and about 4.3 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 cape plumbago change across California?

Yes. WUCOLS rates cape plumbago 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 cape plumbago toxic?

Its sap can cause severe skin irritation, with redness and blistering after contact. Wear gloves and long sleeves when pruning, and wash skin that touches cut stems.

Why does plumbago stick to my clothes?

The seed pods are covered with sticky hairs that cling to clothing and fur. Plant it back from walkways, and trim spent flower clusters near paths.

When should I prune cape plumbago?

Prune in late winter, when it is flowering least. It blooms on the current year's growth, so cutting back then does not cost flowers. Shorten leggy stems any time to control size.

Can cape plumbago climb?

With help, yes. Its long, arching branches can be tied to a fence or trellis and reach close to 20 feet. Left alone, it forms a broad, rounded mound.

Can you overwater cape plumbago?

Yes. It needs fairly well-drained soil, and ground that stays wet harms the roots. Water deeply, then let the upper soil dry before the next round.

Will frost kill cape plumbago?

Frost below about 25 degrees F damages the leaves and stems, but the roots are hardy to around 10 degrees F. Cut out the damage in late winter and new growth will follow.

More plant watering guides

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Sources