WateringTimesWatering plan, $19
Arrhenatherum elatius, WUCOLS IV

How often to water tall oat grass in California

In July in the Central Valley, established tall oat grass needs about 1.9 gallons a week for a plant 2 feet across. Tall oat grass, also called false oat grass, is a perennial grass from Europe, North Africa and southwest Asia. It forms loose tufts of narrow leaves, topped in summer by airy, oat-like flower heads. It grows mainly in the cool seasons and rests after flowering. It wants sun or light shade, regular water and soil that drains well, since heavy wet clay rots it.

Ornamental grassRated for 3 of 6 zones

How often to water tall oat 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 tall oat 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

  • Soil dry 2 inches down around the tufts in warm weather means the grass needs water
  • Tufts rotting out in heavy clay that stays wet point to poor drainage rather than thirst
  • Leaves browning after summer flowering are the normal rest of this deciduous grass
  • Clumps that flop and look tired after bloom need cutting back, not extra water

How to water it

  • Water the base of the tufts with drip or a soaker, wetting the soil about 6 inches deep
  • Let the top inch or two dry before watering again, since soggy soil rots the clumps
  • Plant in well-drained soil, avoiding heavy clay, in full sun on the coast or light shade inland
  • Cut the clumps to the ground after summer flowering to bring on fresh leaves
  • Widen the watered area as the tufts fill in

Through the seasons

Water new plants regularly until they root in. The grass grows mainly from fall through spring, then sends up its airy flower heads in summer. After flowering it browns and rests, and cutting it back then keeps the planting tidy. Though it tolerates fairly dry conditions, it looks better with regular water. WUCOLS rates tall oat grass moderate water in the Central Valley, on the south coast and in South Inland. WUCOLS has not evaluated it for the north-central coast. WUCOLS marks it as not suited to the high desert or the low desert.

In pots

Tall oat grass, especially its compact striped form, can grow in a container that shows off its soft leaves. Use a well-drained, gritty mix and a pot with drainage holes. In summer heat, check the mix every couple of days and water once the top inch is dry. Let the water drain away, then empty the saucer so the roots never stay wet. Cut the tufts back after flowering. In winter, water only when the mix dries.

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
0.671.32.02.70.4JAN0.65FEB1.09MAR1.52APR2.08MAY2.48JUN2.67JUL2.39AUG1.8SEP1.18OCT0.56NOV0.34DEC0.671.32.02.70.4JFM1.52AMJ2.67JAS1.18OND
Gallons per square foot per month, Central Valley. Peak 2.67 in Jul, 17.11 a year.

Monthly water need by climate zone

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

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan–0.40.780.78––
Feb–0.650.810.87––
Mar–1.091.151.3––
Apr–1.521.41.61––
May–2.081.611.95––
Jun–2.481.742.29––
Jul–2.671.982.51––
Aug–2.391.862.33––
Sep–1.81.491.86––
Oct–1.181.151.33––
Nov–0.560.840.9––
Dec–0.340.650.68––
Year–17.1115.518.41––

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 7

Rated moderate water in the Central Valley, like tall oat grass. Plants that drink alike can share one valve and one schedule.

Purple 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 JulySwitch GrassPanicum virgatum ssp. & cvs.moderate 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 tall oat 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 tall oat 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 tall oat grass in summer?

In July, established tall oat 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 tall oat grass need per day?

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

Yes. WUCOLS rates tall oat grass separately for each of the six California climate zones: not evaluated 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, 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.

What is bulbous oat grass?

It is a compact, striped form of tall oat grass, only 8 to 12 inches tall. Its soft, gray-green leaves carry white and blue-green stripes and grow from chains of small bulbous corms. It is soft to the touch and does not spread aggressively.

Should I cut back tall oat grass?

Yes. Cut the clumps to the ground after summer flowering for the best look. Fresh leaves return as the weather cools.

Does tall oat grass grow in shade?

It grows in light shade to full sun. Full sun suits it along the coast, while light shade helps in warmer inland gardens.

Can you overwater tall oat grass?

Yes. Good drainage is a must, and the clumps can rot out in heavy clay. Water regularly, but let the top of the soil dry between waterings.

What other names does tall oat grass go by?

It is also called false oat grass, French rye grass, onion grass and button grass. The compact striped garden form is sold as bulbous oat grass.

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Sources