How often to water giant needle grass in California
In July in the Central Valley, established giant needle grass needs about 0.8 gallons a week for a plant 2 feet across. Giant needle grass, also called giant feather grass, is a dense evergreen grass from Spain that forms a mound of narrow, arching gray-green leaves about 2 feet tall. In spring and early summer, tall stems rise 4 feet or more above it. Airy panicles of long-awned purplish flowers top them, ripening to wheat gold and shimmering in the breeze.
How often to water giant needle 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
- When the clump's soil is dry well below the surface in summer, giant needle grass can take a deep drink
- Leaves browning heavily at the base during a long hot spell can follow a dry root zone
- Flower stems leaning in soggy, rich soil point to too much water
- Seedlings popping up in dry gravel come from its seed and are easy to pull
How to water it
- Water regularly while young, then cut back once established
- Water deeply and infrequently in summer
- Plant in full sun in well-drained soil
- Leave the flower heads into fall, then cut them
- Pull extra seedlings while they are small
Through the seasons
Water new plants regularly until established, then let them go with little irrigation. Flower stems rise in spring and early summer and stay attractive well into fall. It occasionally seeds itself in dry gravel, but seedlings are easy to pull. Giant needle grass gets a low water rating from WUCOLS in South Inland and the Central Valley, and on both the north-central coast and the south coast. The high desert and the low desert have no WUCOLS evaluation for it.
In pots
Giant needle grass can grow in a large, deep pot, though its tall flower stems need room above. Use a well-drained, gritty mix. Water when the top few inches dry, until it drains through. In summer, check every few days, since a big grass in a pot uses water fast. Empty the saucer. Leave the flowers standing into fall. In winter, water only when the mix dries.
- A year
- 6.84 gal per sq ft
- Reference
- Sacramento climate table
- Counts
- Plant need, before sprinkler losses
Monthly water need by climate zone
Giant Needle 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 | 0.15 | 0.16 | 0.31 | 0.31 | – | – |
| Feb | 0.21 | 0.26 | 0.32 | 0.35 | – | – |
| Mar | 0.35 | 0.43 | 0.46 | 0.52 | – | – |
| Apr | 0.47 | 0.61 | 0.56 | 0.64 | – | – |
| May | 0.58 | 0.83 | 0.64 | 0.78 | – | – |
| Jun | 0.64 | 0.99 | 0.69 | 0.92 | – | – |
| Jul | 0.64 | 1.07 | 0.79 | 1 | – | – |
| Aug | 0.6 | 0.95 | 0.74 | 0.93 | – | – |
| Sep | 0.5 | 0.72 | 0.6 | 0.74 | – | – |
| Oct | 0.35 | 0.47 | 0.46 | 0.53 | – | – |
| Nov | 0.19 | 0.22 | 0.33 | 0.36 | – | – |
| Dec | 0.12 | 0.14 | 0.26 | 0.27 | – | – |
| Year | 4.8 | 6.84 | 6.2 | 7.37 | – | – |
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 6
Rated low water in the Central Valley, like giant needle grass. Plants that drink alike can share one valve and one schedule.
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 JulyTurn this into minutes on your water days
Every city page has a calculator that takes giant needle 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 should I water giant needle grass in summer?
In July, established giant needle grass needs about 0.8 gallons in the Central Valley, 0.6 gallons on the south coast and 0.7 gallons in the South Inland zone each week, for a plant 2 feet across. Water deeply and let the top of the soil dry before the next watering. Skip a watering after a soaking rain.
How much water does giant needle grass need per day?
In July in the Central Valley, established giant needle grass 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 giant needle grass change across California?
Yes. WUCOLS rates giant needle grass separately for each of the six California climate zones: low water in the North-Central Coastal zone, low water in the Central Valley zone, low water in the South Coastal zone, low 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.
When does giant needle grass bloom?
Tall flower stems rise in spring to early summer. The awned flowers ripen to a wheat gold. They stay attractive into fall.
Does giant needle grass need much water?
It needs regular water at first, then little irrigation once established. Water deeply in long dry spells. Avoid soggy soil.
Does giant needle grass reseed?
It occasionally seeds itself in the dry garden. Seedlings are easy to pull. It is not usually pesky.
How cold hardy is giant needle grass?
It is hardy to at least 0 degrees F. Cold is not a concern in California. Drainage matters more.
Can I use the flowers in arrangements?
Yes, the flower heads are good in dried arrangements. Cut them when golden. Leave some for garden display.
More plant watering guides
Sources
- WUCOLS IV plant water use classification for Stipa gigantea, 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