WateringTimesWatering plan, $19
Panicum virgatum ssp. & cvs., WUCOLS IV

How often to water switch grass in California

In July in the Central Valley, established switch grass needs about 1.9 gallons a week for a plant 2 feet across. Switch grass is a warm-season prairie grass native to much of North America, forming a dense, upright clump 3 to 4 feet tall. From summer into fall, airy, pink-tinged flower clouds rise above the leaves, and some cultivars reach 7 to 8 feet in bloom. It grows in clay or sand, handles occasional flooding and does best in moist soil and full sun.

Ornamental grassRated for 5 of 6 zones

How often to water switch grass, 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 switch grass and the rest of your yard, on the days your water supplier allows.Get the plan for $19

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.

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

  • Blades wilting or browning at the tips in summer heat, with soil dry a few inches down, mean the clump needs water
  • Clumps flopping open in part shade reflect too little sun, not too little water
  • Tan, dry foliage through winter is normal, since the leaves fade and stand until you cut them back
  • Rust spots on the leaves in hot summers point to a fungal disease rather than thirst
  • Yellowing, rotting crowns in soil that stays soggy point to crown or root rot, a risk when the plant is stressed

How to water it

  • Water at the base of the clump with drip or a soaker, wetting the soil 8 to 12 inches deep
  • Let the top couple of inches dry before the next watering, especially in heavy clay
  • Plant in full sun in clay or sandy soil, since part shade gives a looser, floppier clump
  • Cut the clump back hard in late winter, before new growth starts
  • Widen the watered area slowly as rhizomes thicken the clump, and divide it in spring when needed

Through the seasons

Water new plants regularly through their first summer while the roots spread. Established clumps grow mainly in warm weather and want deep, regular watering through the dry months. Flowers rise from summer into fall, and leaves turn yellow to orange before fading to tan and standing through winter. Cut the clump back in late winter. WUCOLS rates switch grass moderate water on the north-central coast, in the Central Valley and on the south coast. South Inland and the high desert share that moderate water rating. WUCOLS has not evaluated it for the low desert.

In pots

Switch grass grows well in a large, deep container, where its upright form makes a tall screen on a patio. Use a loam-based mix and a pot with drainage holes. Through hot weather, feel the mix every day or two, and water thoroughly when the top inch is dry. Drain the saucer after each watering. Cut the old foliage down in late winter. While the clump rests in winter, water only enough to keep the mix from drying out completely.

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

Switch Grass: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.40.780.780.74–
Feb0.530.650.810.870.93–
Mar0.871.091.151.31.46–
Apr1.181.521.41.611.89–
May1.462.081.611.952.39–
Jun1.612.481.742.292.85–
Jul1.612.671.982.513.04–
Aug1.492.391.862.332.79–
Sep1.241.81.491.862.14–
Oct0.871.181.151.331.46–
Nov0.470.560.840.90.93–
Dec0.310.340.650.680.65–
Year1217.1115.518.4121.27–

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 switch grass. Plants that drink alike can share one valve and one schedule.

Tall Oat GrassArrhenatherum elatiusmoderate water, Central Valley2.67 gal/sq ft in JulyPurple Moor GrassMolinia caeruleamoderate water, Central Valley2.67 gal/sq ft in JulySheep FescueFestuca ovina and cvs.moderate water, Central Valley2.67 gal/sq ft in JulyCreeping Red FescueFestuca rubra ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyEulalia GrassMiscanthus sinensis ssp. & cvsmoderate water, Central Valley2.67 gal/sq ft in JulyBlack PennisetumPennisetum alopecuroides ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyBlood GrassImperata cylindrica ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in July

Similar plants that need less water 7

Rated lower than switch 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 JulyTufted HairgrassDeschampsia cespitosa and cvs.low water, Central Valley1.07 gal/sq ft in JulyJune GrassKoeleria macrantha (cristata)low water, Central Valley1.07 gal/sq ft in JulyFalse Esparto GrassLygeum spartumlow water, Central Valley1.07 gal/sq ft in JulyBlue FescueFestuca glauca ssp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyBaltic RushJuncus balticuslow water, Central Valley1.07 gal/sq ft in JulyGiant Needle GrassStipa gigantealow 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 switch 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 switch grass in summer?

In July, established switch grass needs about 1.9 gallons in the Central Valley, 1.4 gallons on the south coast and 1.8 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 switch grass need per day?

In July in the Central Valley, established switch 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 switch grass change across California?

Yes. WUCOLS rates switch 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, moderate water in the South Coastal zone, moderate water in the South Inland zone, moderate water 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 should I cut back switch grass?

Cut it back hard in late winter or early spring, before new shoots appear. Leaving the dried leaves and seed heads through winter feeds birds and small mammals.

Why is my switch grass falling over?

Too much shade is the usual cause, since plants in part shade grow looser and may flop over. Move it to full sun or choose a more compact cultivar.

Is switch grass a fire risk?

Yes. It has a high flammability rating, and its dry foliage stands through winter. Plant it away from the house and cut it back in late winter.

Does switch grass spread?

It spreads slowly by short rhizomes and may self-sow. It forms a dense clump rather than running through a bed.

Which switch grass turns red?

'Shenandoah' and 'Prairie Fire' start blue-green and turn dark reddish purple in summer. Tall cultivars such as 'Blue Tower' and 'Cloud Nine' reach up to 8 feet in flower.

Can switch grass grow in wet soil?

Yes. It grows wild along moist roadsides and streambanks and withstands occasional flooding. It also works as an accent along a pond.

More plant watering guides

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Sources