· Michael Blair
Frequent light watering trains roots to stay near the surface, where the soil dries first. Deep infrequent watering does the opposite, and in a Middle Tennessee summer that difference decides whether a lawn survives July.
The number
Roughly an inch a week including rainfall for actively growing fescue, delivered in one or two soakings rather than daily sprinklings.
Measure it rather than guess: put a few straight-sided tins around the zone, run it, and time how long it takes to collect an inch. Most people find their system is far off what they assumed.
Time of day
Early morning, finishing around sunrise. Evening watering leaves foliage wet overnight, which in Nashville humidity is an invitation to brown patch.
Midday watering loses a substantial share to evaporation before it reaches the root zone.
- About an inch a week including rain
- One or two deep soakings, not daily
- Finish watering around sunrise
- Measure output with tins rather than estimating
- Cycle and soak on clay to avoid runoff
Cycle and soak on clay
Middle Tennessee clay absorbs slowly. Running a zone for thirty minutes straight produces runoff for the last twenty of them.
Splitting it into shorter cycles with an hour between lets the water soak in. Most modern controllers do this automatically if configured.
Dormancy changes everything
Once fescue is dormant in high summer, watering will not green it up. Half an inch every two to three weeks keeps the crown alive, which is all you are trying to do.
Continuing a full irrigation schedule on a dormant lawn wastes a great deal of water for no benefit.