WateringTimesWatering plan, $19
Saponaria ocymoides, WUCOLS IV

How often to water rock soapwort in California

In July in the Central Valley, established rock soapwort in loam needs a deep watering about every 20 days: about 2.2 gallons each time for a plant 2 feet across, about 0.8 gallons a week. Rock soapwort is a low, trailing perennial from the rocky mountain slopes of southern Europe. Reddish stems and small gray-green leaves form a mat that cascades over walls. Small bright pink flowers cover it from late spring into summer. It wants sharp drainage and tolerates some drought once established.

Ground coverPerennialRated for 4 of 6 zones

How often to water rock soapwort, 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 rock soapwort 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 2 to 3 inches down beneath the mat means it is time to water
  • Gray-green leaves that turn limp and dull in afternoon heat, with dry soil below, point to thirst
  • Stems that blacken or collapse at the base over soggy soil point to too much water for this rock garden plant
  • Ragged, holed leaves after damp weather point to slugs or snails rather than a watering problem
  • Sparse, leggy stems after bloom call for shearing, not more water

How to water it

  • Water rock soapwort at the base of the mat with drip or a gentle hose rather than overhead spray
  • Soak the soil about 6 inches deep, then let it dry 2 inches down before the next watering
  • Plant it in gravelly, well-drained soil that is neutral to alkaline, or at the top of a wall or slope
  • Mulch around the mat with gravel rather than bark, in keeping with its rock and gravel garden habit
  • Shift drip emitters to the edge of the mat as it spreads toward its full width of 1 to 2 feet

Through the seasons

Water a new rock soapwort through its first summer until the mat knits into the soil. Once established it tolerates some drought. It keeps some of its leaves through winter and blooms from late spring into summer. Shear it back by about half after flowering to keep it compact and coax more bloom. Winter rain covers the cool months on the north-central coast and in the Central Valley, where WUCOLS rates it low water. It rates moderate water on the south coast and in South Inland, where summer checks matter most. WUCOLS marks it as not suited to the high desert or the low desert.

In pots

Rock soapwort suits containers, where its stems trail over the rim. Use a gritty, fast-draining mix and a pot with open drainage holes. Check the mix 1 to 2 inches down every few days in summer, and daily in South Inland heat. Water until it drains from the holes, then empty the saucer. A small pot on hot paving dries fast, so give it some afternoon shade inland. In winter, let the mix dry between waterings and keep the pot out of standing rain.

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

Rock Soapwort: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.150.160.780.78––
Feb0.210.260.810.87––
Mar0.350.431.151.3––
Apr0.470.611.41.61––
May0.580.831.611.95––
Jun0.640.991.742.29––
Jul0.641.071.982.51––
Aug0.60.951.862.33––
Sep0.50.721.491.86––
Oct0.350.471.151.33––
Nov0.190.220.840.9––
Dec0.120.140.650.68––
Year4.86.8415.518.41––

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 rock soapwort. Plants that drink alike can share one valve and one schedule.

BougainvilleaBougainvillea & spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyAgapanthusAgapanthus orientalislow water, Central Valley1.07 gal/sq ft in JulyGeraniumsPelargonium x hortorum and 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 JulyIrisesIris germanicalow 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 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 JulySagebrushArtemisia spp. (shrubby)low 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 July
Minutes for your sprinklers

Turn this into minutes on your water days

Every city page has a calculator that takes rock soapwort, 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 rock soapwort in summer?

In July, established rock soapwort in loam needs a deep watering about every 20 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 rock soapwort need per day?

In July in the Central Valley, established rock soapwort 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 rock soapwort change across California?

Yes. WUCOLS rates rock soapwort separately for each of the six California climate zones: low 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 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.

When should I cut back rock soapwort?

Shear it back by about half right after flowering. This keeps the mat compact and can bring another flush of bloom. A trim in late winter or early spring also renews a tired plant.

Does rock soapwort spread by seed?

Yes, it self-sows readily. Seedlings can turn up nearby, but the plant is not considered aggressive. Pull unwanted seedlings while they are small.

Can I walk on rock soapwort?

Not often. It can grow between stepping stones, but it does not tolerate heavy foot traffic. Wall tops, edges and rock gardens suit it better.

Is rock soapwort deer resistant?

It is listed as tolerant of deer. No plant is fully deer proof, so hungry deer may still nibble young plants.

Why is it called soapwort?

The genus name comes from the Latin word for soap. The species name means resembling basil, likely for its leaf shape or branching habit.

More plant watering guides

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Sources