October 1, 2026

How to run a garden irrigation system by which zone is dry

A garden irrigation system carries water to your beds on a schedule. Drip lines, soaker hose, or sprinklers all run every zone on the same timer unless a reading tells you which bed has gone dry. Two signals decide a smart run: a per-bed soil reading tells you which zone is thirsty, and recent plus forecast rain tells you whether to run at all.

Choose the delivery hardware

For vegetable beds, drip lines and soaker hose put water at the root zone and lose little to evaporation. Sprinklers cover lawns and dense plantings. The hardware matters less once you can split it by bed, so group your valves the way your beds dry. For the trade-offs between types, see our guide on which watering system to pick and what it can't sense.

• Drip or soaker for beds. Delivers water slowly at the root zone where vegetables use it.
• Sprinkler for lawn. Covers wide, even areas that don't need targeting.
• One valve per bed group. Lets you open water for the zone that reads dry and leave the rest closed.

How to run it where the water is needed

These steps assume a soil probe in each bed and a connected weather station. A probe reads the moisture at the root zone; the station feeds the rain signal. Work through them in order.

• Map a sensor to each bed. In the station screen, assign each soil channel to the bed it sits in. Any garden member can do this, and only a mapped sensor counts toward a dry alert. See connecting a soil sensor per bed.
• Learn the dry trigger. A capacitive probe fires a dry alert when the two most recent readings are both below 25%. A Watermark tension probe fires when both read above 60 cb. Every bed uses the same 25% default, so a fast-draining bed trips first.
• Check the rain guidance before a run. The garden-level guidance on Today says hold when 5 mm or more of rain is forecast over today and tomorrow, and covered when 5 mm or more fell in the last three days. In our own garden July brought 10.89 inches of rain, enough that frequent real rain would often put the guidance on hold or covered.
• Open the valve for the flagged bed. When a bed reads dry and the rain guidance says water, run that zone and leave the beds still above threshold closed.
• Confirm the reading climbs. After the run, watch the next soil reading rise. A flat reading means the water missed the root zone or the line clogged.

This is the per-zone version of a drip setup. For the hardware side of running lines only where the soil is dry, see running a drip system where soil is dry and deciding which valve to open.

What can go wrong

The reading guides the run, and a few things break the link between them.

• A probe in the wrong spot. A sensor near a dripper reads wet while the rest of the bed stays dry. Place it in the root zone, away from an emitter.
• One threshold for every bed. No screen sets a per-bed dryness number; every bed uses 25%. A bed that naturally holds more water may flag late.
• Garden-wide rain, bed-by-bed dryness. Rain guidance covers the whole garden, so a covered garden can still hold one dry bed under a dense canopy. Trust the bed's reading over the garden signal when they disagree.

Start by putting one probe in your driest-running bed and watching it for a week against your current schedule. If it drops below 25% days before your timer fires, move that zone off the clock and onto the reading. Our guide on what a soil sensor does for irrigation covers the next bed.