How often to water purple spurge in California
In July on the north-central coast, established purple spurge in loam needs a deep watering about every 9 days: about 1.5 gallons each time for a plant 2 feet across, about 1.1 gallons a week. Purple spurge is a clump-forming perennial about 2 feet tall with lance-shaped leaves, deep purple in the popular form, that turn red in fall. Small yellow flowers with colorful bracts appear in early summer and draw bees. It tolerates dry soil but grows best in moist, humus-rich ground, and its milky sap irritates skin and eyes.
How often to water purple spurge, month by month
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.
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.
How to tell it needs water
- Soil dry 2 inches down beside the clump in summer signals purple spurge needs a drink
- Purple leaves hanging limp and losing their gloss can indicate thirst
- Lower leaves dropping in midsummer can follow a dry root zone
- Gray, fuzzy mold on stems in damp, crowded spots points to gray mold from wet conditions
How to water it
- Water the soil around the clump with drip or a gentle hose, not over the leaves
- Soak 6 to 8 inches down, then let the top inch or two dry
- Plant in humus-rich soil in full sun to light dappled shade
- Space plants for air flow, since gray mold can strike crowded clumps
- Wear gloves when you divide or trim it, since the sap irritates skin
Through the seasons
Keep a new plant evenly moist until it settles, then water when the upper soil dries. Established clumps tolerate dry soil, yet they grow best in moist, humus-rich ground. It is deciduous, with leaves turning red in fall before the plant dies back for winter. New shoots return in spring, followed by early summer flowers. Winter rain covers the dormant season along the coast. WUCOLS rates purple spurge moderate water on the north-central coast. WUCOLS has not evaluated it for the Central Valley, the south coast, South Inland, the high desert or the low desert.
In pots
Purple spurge makes a strong foliage accent in a mid-size pot of rich, well-drained mix. Feel the mix an inch or two down and water once it is dry, letting excess drain out the bottom. In warm weather that may be every few days. Empty the saucer so roots stay healthy. Tidy the plant after flowering, with gloves on. The clump dies back in winter, so water only lightly until new shoots appear.
- A year
- no figure
- Reference
- Sacramento climate table
- Counts
- Plant need, before sprinkler losses
WUCOLS lists Purple Spurge as not evaluated for the Central Valley zone, so no monthly figure is computed here.
Monthly water need by climate zone
Purple Spurge: gallons per square foot per month, by WUCOLS climate zone
| Month | N. Coast | C. Valley | S. Coast | S. Inland | Hi Desert | Lo Desert |
|---|---|---|---|---|---|---|
| Jan | 0.37 | – | – | – | – | – |
| Feb | 0.53 | – | – | – | – | – |
| Mar | 0.87 | – | – | – | – | – |
| Apr | 1.18 | – | – | – | – | – |
| May | 1.46 | – | – | – | – | – |
| Jun | 1.61 | – | – | – | – | – |
| Jul | 1.61 | – | – | – | – | – |
| Aug | 1.49 | – | – | – | – | – |
| Sep | 1.24 | – | – | – | – | – |
| Oct | 0.87 | – | – | – | – | – |
| Nov | 0.47 | – | – | – | – | – |
| Dec | 0.31 | – | – | – | – | – |
| Year | 12 | – | – | – | – | – |
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 purple spurge. Plants that drink alike can share one valve and one schedule.
Lilyleaf LadybellsAdenophora liliifolianot rated, Central Valleyno Central Valley rating
ArnicaArnica montananot rated, Central Valleyno Central Valley rating
Frilly BergeniaBergenia ciliatanot rated, Central Valleyno Central Valley rating
Cabbage on a StickBrighamia insignisnot rated, Central Valleyno Central Valley rating
Basket PlantCallisia fragransnot rated, Central Valleyno Central Valley rating
Forest SedgeCarex sylvaticanot rated, Central Valleyno Central Valley rating
Umbrella DracaenaDianella ensifolianot rated, Central Valleyno Central Valley rating
Rusty FoxgloveDigitalis ferrugineanot rated, Central Valleyno Central Valley rating
Big-Flowered FoxgloveDigitalis grandifloranot rated, Central Valleyno Central Valley rating
Woolly FoxgloveDigitalis lanatanot rated, Central Valleyno Central Valley rating
Sunset FoxgloveDigitalis obscuranot rated, Central Valleyno Central Valley rating
Male FernDryopteris filix-masnot rated, Central Valleyno Central Valley rating
Alpine Sea HollyEryngium alpinumnot rated, Central Valleyno Central Valley rating
Queen of the MeadowFilipendula ulmarianot rated, Central Valleyno Central Valley rating
DropwortFilipendula vulgaris (Filipendula hexapetala)not rated, Central Valleyno Central Valley rating
GentianGentiana scabra procumbensnot rated, Central Valleyno Central Valley ratingTurn this into minutes on your water days
Every city page has a calculator that takes purple spurge, 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 much water does purple spurge need per day?
In July on the north-central coast, established purple spurge needs about 0.2 gallons a day for a plant 2 feet across and about 0.7 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 purple spurge change across California?
Yes. WUCOLS rates purple spurge separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, not evaluated in the Central Valley zone, not evaluated in the South Coastal zone, not evaluated 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.
Is purple spurge sap dangerous?
The milky sap irritates skin and eyes, and the plant is harmful if eaten. Wear gloves and eye protection when cutting it. Keep it away from where children play.
Does purple spurge change color?
Yes, the purple leaves turn red in fall. Bracts around the small flowers add color in early summer.
Can purple spurge grow in dry soil?
It tolerates dry soil, but it grows best in moist, humus-rich ground. In dry spells it may look tired. A deep soak usually revives it.
How do I divide purple spurge?
Divide it in early spring as growth begins. Basal cuttings in spring or early summer also root well. Wear gloves to avoid the sap.
What pests bother purple spurge?
Aphids may be troublesome, and gray mold can appear in damp conditions. Water the soil, not the leaves. Thin crowded clumps.
More plant watering guides
Sources
- WUCOLS IV plant water use classification for Euphorbia dulcis, the University of California survey California agencies use for landscape plan reviewRead August 23, 2026 on wucols.ucdavis.edu
- Model Water Efficient Landscape Ordinance, adopted text and appendices, effective 2025-01-02 · monthly reference evapotranspiration per city, Appendix CRead August 23, 2026 on water.ca.gov/-/media/DWR-Website/Web-Pages/Programs/Water-Use-And-Efficiency/MWELO-Rulemaking/Final-MWELO-Text-and-Appendices_20250103.pdf
- UC Statewide IPM Program, irrigation scheduling using evapotranspirationRead September 30, 2026 on ipm.ucanr.edu/PMG/GARDEN/ENVIRON/evap.html
- Shaw and Pittenger, Landscape Irrigation System Evaluation and Management, UC Cooperative Extension, 2009Read September 30, 2026 on ucanr.edu/sites/default/files/2013-02/160836.pdf
- Pittenger, Water Management in Gardens and Landscapes, UC Riverside, 2017Read September 30, 2026 on ucanr.edu/sites/default/files/2017-03/258022.pdf