How long can dormant grass go without water?

Grass enters a dormant state during hot, dry periods in order to conserve water and energy. During dormancy, the grass becomes less active and grows very little, if at all. Dormant grass turns brown and appears dead, but the crowns and roots remain alive. This allows the grass to survive extended periods without water. However, dormant grass still requires some minimal amount of moisture to survive.

How long can dormant grass survive without water?

Most experts agree that dormant grass can survive 4-6 weeks without any water at all. However, this depends on several factors:

  • Grass species – Warm season grasses like bermudagrass and zoysia are more drought tolerant than cool season grasses like fescue and ryegrass.
  • Health of the grass – Grass in poor health before drought has less reserves to survive an extended dry period.
  • Soil type – Grass growing in sandy soils will require more frequent watering than grass in heavy clay soils which retain more moisture.
  • Temperature – Hot, dry conditions cause grass to use water reserves faster than cooler weather.
  • Last irrigation – Grass that went into dormancy with adequate soil moisture will survive longer without water.
  • Rainfall – Occasional rainfall of 1/4″ or more will extend the survival time.
  • Leaf moisture – Grass with some remaining leaf moisture will last longer than completely dried leaves.

These factors make it difficult to give an exact number of weeks that grass can survive drought while dormant. However, most grasses should be able to go 4-6 weeks during summer dormancy without irrigation in average conditions. Extended periods beyond this risk desiccation and death of the crowns and roots.

What happens when dormant grass gets no water at all?

As the drought period continues with no rainfall or irrigation, the dormant grass will eventually use up its reserves of moisture and carbohydrates stored in the roots and crowns. The leaves and stems continue to lose moisture and turn brown. After several weeks, the crowns and roots will also dry out.

Desiccation of the crowns is fatal for the grass plants. The crowns contain the growing points (meristems) that allow the grass to produce new shoots and leaves. When the crowns completely dry out, these growing points die. The root system may also shrink as the roots die back from lack of moisture.

At this point, the grass has passed the point of no return. Even if rain finally comes, the grass plants are dead and will not regrow. The pasture or lawn will be bare dirt or require reseeding to restore growth.

Visual signs of severe drought stress

  • All leaf blades are completely brown and dry with no green remaining
  • Leaf blades easily pull away from sheaths
  • Crowns are brown, dry and brittle
  • Roots are brown and minimal; lack white, moist interiors

How long does it take for drought-stressed grass to green up again?

If rainfall or irrigation comes before reaching the point of no return, the dormant grass will eventually revive and regrow. However, severely drought-stressed grass will be slow to recover and regreen after dry conditions. It takes time for the grass crowns and roots to take up moisture again and resume growth.

The length of time for dormant grass to turn green again after watering depends on several factors:

  • Severity of drought – Grass barely hanging on will green faster than completely dried grass
  • Soil moisture – Wet soils allow faster regreening than still dry soils after rain/irrigation
  • Species – Warm season grasses green faster than cool season species
  • Leaf health – Leaves retaining some moisture regreen faster than dead leaves
  • Crown/root health – Damaged or minimal crowns/roots delay regrowth
  • Temperatures – Warm weather accelerates regreening vs. cool temperatures
  • Time of year – Grasses green faster in spring vs. summer/fall dormancy

Under ideal conditions with mild drought stress, water and warm temperatures, dormant grass may fully regreen within 1-2 weeks. But under severe drought stress, it may take 2-3 months for dormant grass to fully turn green again after receiving water. Completely dried out grass may fail to regrow at all once the crowns have died.

How much water does dormant grass need for recovery?

Apply enough water to thoroughly moisten the root zone when reviving drought-stressed grass. Soils should be wet to a depth of 4-6 inches to supply moisture to the deepest roots.

Typical water requirements for regreening dormant grass:

  • Moderate drought stress – 1-1.5 inches of water immediately.
  • Severe drought conditions – 2+ inches of water applied gradually over 2-3 applications. Avoid runoff.
  • Sandy soils – May require more frequent, lighter irrigation due to faster moisture loss.
  • Clay soils – Absorb water slowly; irrigate deeply but infrequently.

Check soil moisture before each application. Continue watering until the root zone stays consistently moist but not saturated. Once the grass has fully turned green again, water can be cut back to typical amounts to maintain active growth.

Is fertilizer needed when dormant grass regreens?

Fertilizing drought-stressed grass too soon can damage crowns and roots. Grass needs time to recover its vigor before resuming active growth. Wait until the grass has completely greened up before fertilizing:

  • Cool-season grasses: Wait at least 2-4 weeks after greenup to fertilize.
  • Warm-season grasses: Wait 4-6 weeks after full greenup before fertilizing.

A light fertilization can help the grass redevelop its root system faster after a dormancy period. But heavy fertilization on weakened grass can burn crowns. Apply a balanced, complete fertilizer at half the normal rate. Only make a second application after another 3-4 weeks if grass shows vigor.

Should dormant grass be watered before it browns completely?

It’s best to allow grass to go dormant on its own before drought conditions reach severe levels. Dormancy is a protective mechanism for the grass. However, lightly watering dormant grass can extend its survival during prolonged dry periods:

  • Apply 1/4-1/2 inch of water every 2-3 weeks before complete browning.
  • This light watering maintains crown moisture without pushing new growth.
  • Time watering for very early morning to reduce evaporation loss.
  • Avoid runoff so all water soaks into the root zone.

Judicious light watering gives dormant grass a little extra drought protection. But avoid frequent or heavy irrigation that disrupts dormancy before severe drought threatens the crowns. Letting grass go fully dormant develops deeper, more drought resilient roots over time.

When to allow grass to go dormant vs. continuing irrigation

It’s a balancing act between conserving water and keeping grass alive during drought. Allowing full dormancy prevents water waste, but risks crown death after prolonged drought. Here are some guidelines on when to water drought-stressed grass vs. letting it go dormant:

  • Let grass go dormant if drought conditions expected to last 4-6 weeks.
  • Resume irrigation if over 6-8 weeks without rain is forecast.
  • Water lightly every 2-3 weeks before complete dormancy sets in.
  • Continue irrigation on slopes/banks to avoid erosion.
  • Prioritize watering sections of lawn that are more vulnerable.
  • Reduce irrigation frequency/amounts to promote deeper roots.

Knowing the typical drought duration, grass species and soil types can guide decisions on allowing dormancy. Temporary irrigation can maintain grass through short-term drought. But extended hot, dry periods may require allowing dormancy to prevent plant loss.

How can dormant grass better survive drought?

Proper care when grass is actively growing makes it better able to withstand drought stress and survive dormancy when water is limited:

  • Mow at taller heights – Longer grass blades allow deeper roots.
  • Aerate soil regularly – Reduces compaction and allows better root growth.
  • Apply fertilizer conservatively – Avoid excessive growth that needs more water.
  • Use slow-release fertilizers – Provides longer-lasting nutrients with less growth surge.
  • Seed in fall – Spring seeded grass has less established roots going into summer.
  • Allow moderate drought stress between watering – Triggers deeper root growth.
  • Mulch clippings – Returns moisture and nutrients back to the soil.

Grass varieties bred for improved drought tolerance are also more likely to survive extended dormancy. Local turfgrass experts can advise on best cultivars for your climate and conditions.

Conclusion

Dormant grass can typically survive 4-6 weeks without water before crown desiccation risks plant death. Severely drought-stressed grass takes longer to regreen after rainfall or irrigation and may require careful recovery management. Judicious light watering can help extend survival during short-term droughts. But allowing deep dormancy enhances drought resilience and reduces irrigation demand during hot, dry spells.

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