How often to water purple moor grass in California
In July in the Central Valley, established purple moor grass needs about 1.9 gallons a week for a plant 2 feet across. Purple moor grass forms a slow-growing clump of narrow leaves. In midsummer, airy, purple-tinted flower stalks rise well above the foliage. It comes from moors, bogs and lakeshores in Europe and likes soil that stays moist. The whole clump turns golden in fall before it collapses for winter.
How often to water purple moor grass, 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: the plant’s WUCOLS rating times your city’s climate for the month, over the area the plant covers. Skip a watering after a good soaking rain.
How to tell it needs water
- Soil dry 2 inches down at the edge of a moor grass clump signals that it needs a soak
- Narrow leaves rolling in and browning at the tips in summer can mean the clump has dried, since it comes from wet moorland
- Few or short flower stalks in a hot summer reflect heat as much as thirst, because this grass flowers poorly in hot weather
- Yellow leaves and a soft, dark crown in soil that stays saturated can indicate poor drainage rather than thirst
- Gold fall color followed by tan, flattened foliage is the normal end of the season, not drought damage
How to water it
- Water at the base of the clump with drip or a soaker line, wetting a ring a little wider than the leaves
- Soak the soil about a foot deep, then water again when the top 2 inches turn dry
- Mulch around the clump with shredded bark to keep the roots cool, leaving the crown itself uncovered
- Plant it in full sun in fertile, slightly acidic to neutral soil that holds moisture yet drains, adding compost to sandy ground
- Widen the soaked ring slowly as the clump fills out, since it can take two or three years to reach full size
Through the seasons
A new purple moor grass grows slowly and can take two or three years to settle. Keep its root ball and the soil around it moist through those first summers. Established clumps still need soil checks from spring growth through late summer flowering. The foliage colors gold in fall, falls over, and the clump rests until new blades appear in early spring. Winter rain covers the dormant months on the north-central coast and in the Central Valley. WUCOLS rates purple moor grass moderate water on the north-central coast and in the Central Valley. WUCOLS has not evaluated it for the south coast, South Inland, the high desert or the low desert.
In pots
Purple moor grass suits a large container, where its fine leaves and tall flower stalks show well. Its moorland roots dislike drying out, so check the mix every few days in summer and daily during inland heat. Water until it drains from the holes, and pour off the saucer afterward. After the foliage turns tan and is cut back, the dormant clump needs only enough water to keep the mix from going bone dry. Divide an old, crowded clump in spring.
- A year
- 17.11 gal per sq ft
- Reference
- Sacramento climate table
- Counts
- Plant need, before sprinkler losses
Monthly water need by climate zone
Purple Moor Grass: 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 | 0.4 | – | – | – | – |
| Feb | 0.53 | 0.65 | – | – | – | – |
| Mar | 0.87 | 1.09 | – | – | – | – |
| Apr | 1.18 | 1.52 | – | – | – | – |
| May | 1.46 | 2.08 | – | – | – | – |
| Jun | 1.61 | 2.48 | – | – | – | – |
| Jul | 1.61 | 2.67 | – | – | – | – |
| Aug | 1.49 | 2.39 | – | – | – | – |
| Sep | 1.24 | 1.8 | – | – | – | – |
| Oct | 0.87 | 1.18 | – | – | – | – |
| Nov | 0.47 | 0.56 | – | – | – | – |
| Dec | 0.31 | 0.34 | – | – | – | – |
| Year | 12 | 17.11 | – | – | – | – |
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 7
Rated moderate water in the Central Valley, like purple moor grass. Plants that drink alike can share one valve and one schedule.
Tall Oat GrassArrhenatherum elatiusmoderate water, Central Valley2.67 gal/sq ft in July
Sheep FescueFestuca ovina and cvs.moderate water, Central Valley2.67 gal/sq ft in July
Creeping Red FescueFestuca rubra ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in July
Eulalia GrassMiscanthus sinensis ssp. & cvsmoderate water, Central Valley2.67 gal/sq ft in July
Switch GrassPanicum virgatum ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in July
Black PennisetumPennisetum alopecuroides ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in July
Blood GrassImperata cylindrica ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulySimilar plants that need less water 7
Rated lower than purple moor grass in the Central Valley. Worth a look for a new bed or a lawn replacement.
Quaking GrassBriza medialow water, Central Valley1.07 gal/sq ft in July
Tufted HairgrassDeschampsia cespitosa and cvs.low water, Central Valley1.07 gal/sq ft in July
June GrassKoeleria macrantha (cristata)low water, Central Valley1.07 gal/sq ft in July
False Esparto GrassLygeum spartumlow water, Central Valley1.07 gal/sq ft in July
Blue FescueFestuca glauca ssp. & cvs.low water, Central Valley1.07 gal/sq ft in July
Baltic RushJuncus balticuslow water, Central Valley1.07 gal/sq ft in July
Giant Needle GrassStipa gigantealow water, Central Valley1.07 gal/sq ft in JulyTurn this into minutes on your water days
Every city page has a calculator that takes purple moor grass, 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 moor grass need per day?
In July in the Central Valley, established purple moor grass needs about 0.3 gallons a day for a plant 2 feet across and about 1.1 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 moor grass change across California?
Yes. WUCOLS rates purple moor grass separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, moderate water 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.
Why is my purple moor grass not flowering?
This grass flowers best where summers stay cool, and blooms are modest in hot, dry weather. Young clumps also need two or three years before they flower freely. Extra water will not cancel heat, but a dry root zone adds to the problem.
When should I cut back purple moor grass?
Cut the old foliage to the ground in late winter or early spring, just before new blades emerge. Much of it breaks off on its own in late fall. The clump uses little water until fresh growth starts, so check the soil before the first spring soak.
Can purple moor grass grow beside a pond?
Yes. It grows wild in bogs and along lakes and tolerates wet soil. Set it at the moist edge with the crown above the waterline rather than in standing water.
Is purple moor grass slow to establish?
Yes, it can take two to three years to fill in and flower well. Keep the soil evenly moist through that period rather than pushing growth with fertilizer. A small, leafy first year is normal.
Will purple moor grass spread through the garden?
No. It grows as a slow, tidy clump and does not run. Divide it in spring when you want more plants, and water the divisions as you would a new planting.
More plant watering guides
Sources
- WUCOLS IV plant water use classification for Molinia caerulea, 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