Autumn Irrigation Settings: Reduce Water Use and Protect Your Garden

As temperatures begin to cool and autumn arrives, it's important to review your irrigation settings. Many irrigation systems are programmed during the warmer months when plants require frequent watering. However, as seasonal conditions change, continuing to irrigate at summer levels can lead to wasted water, overly wet soil, and unhealthy plants.

Making a few simple adjustments to your irrigation schedule will help maintain plant health while avoiding overwatering.

What Changes in Autumn?

Several natural factors influence how much water your garden actually needs during autumn.

Cooler Soil Temperatures

As soil temperatures drop, plant roots slow their activity. This means plants absorb water more slowly, so irrigation applied at summer levels may remain in the soil longer than needed.

Excess moisture around plant roots can reduce oxygen availability in the soil and may contribute to root stress or disease.

Increased Rainfall

Autumn often brings more frequent rainfall in many parts of New Zealand. Even light but regular rain events can significantly contribute to soil moisture levels.

If irrigation schedules are not adjusted to account for this natural rainfall, it can result in oversaturated soils and wasted water.

Installing a rain sensor or regularly adjusting irrigation timers can help prevent unnecessary watering after rainfall.

Lower Evapotranspiration Rates

Evapotranspiration is the process by which water is lost from soil through evaporation and from plants through transpiration.

In summer, heat, sunlight and wind cause water to be lost quickly. In autumn, cooler temperatures and shorter days mean water stays in the soil for longer, reducing the need for frequent irrigation.

Slower Plant Growth

Many plants begin to slow their growth as daylight hours shorten. While they still require moisture, their demand for water is lower than during peak growing periods.

Continuing to irrigate heavily during this time can lead to overly soft plant growth, increased disease pressure, and weaker root systems.

Why Over-Watering Can Be Harmful

Applying too much water during cooler months can create several problems:

• Increased fungal and disease pressure in lawns and garden beds

• Reduced oxygen around plant roots

• Greater risk of root rot

• Soft, disease-prone growth in vegetables

• Unnecessary water consumption and higher running costs

Healthy plants rely on a balance of moisture, oxygen, and nutrients in the soil. Excess irrigation disrupts that balance.

Signs Your Irrigation System May Be Overwatering

Homeowners often don’t realise when irrigation is applying too much water. Watch for these signs:

• Soggy areas that remain wet long after watering

• Fungal diseases appearing in lawns or vegetable gardens

• Yellowing plant leaves despite regular watering

• Water pooling or runoff during irrigation cycles

If you notice these issues, reducing irrigation frequency or adjusting sprinkler coverage can often resolve the problem.

Recommended Autumn Irrigation Adjustment

As a general guideline, reducing your irrigation schedule to around 75% of your summer watering levels is a good starting point for autumn.

This adjustment helps maintain adequate moisture while preventing oversaturation.

Keep in mind that autumn weather can still include warm, windy days, and some plants will continue active growth for several weeks. Monitoring soil moisture and plant condition will help you fine-tune your settings.

Don’t Forget Daylight Savings Adjustments

Another important seasonal check is ensuring your irrigation controller is adjusted for daylight saving time.

If your timer hasn’t been updated, your irrigation cycle may now be running at an unintended time of night or early morning.

Incorrect timing can increase the risk of watering during colder periods when frost is more likely.

Using Irrigation to Help Protect Frost-Sensitive Plants

Irrigation timing can also help protect vulnerable plants from frosts. Running irrigation 1–2 hours before the coldest part of the night can provide some protection for frost-tender plants. Moist soil retains heat more effectively than dry soil, which can help moderate temperature drops around plant roots.

Checking local weather forecasts can help determine when frost conditions may occur so you can adjust irrigation timing accordingly.

A Simple Autumn Irrigation Checklist

At the start of the season, take a few minutes to check the following:

✔ Reduce irrigation runtime to approximately 75% of summer settings

✔ Adjust timers for daylight saving changes

✔ Check irrigation is not running immediately after rainfall

✔ Inspect sprinkler heads for blockages or leaks

✔ Monitor soil moisture to avoid oversaturation

✔ Consider adjusting watering time to support frost protection

Need Help with Your Irrigation System?

Seasonal adjustments are one of the simplest ways to maintain a healthy garden while using water efficiently.

If you're unsure whether your irrigation system is running correctly, a professional irrigation check can identify issues such as incorrect settings, leaks, blocked sprinklers or poor coverage.

At WTS, we help homeowners and businesses ensure their irrigation systems are set up for the season, delivering the right amount of water where it’s needed.

Contact us for a consultation on your irrigation requirements.