Proper Lawn Watering Practices in the Pacific Northwest
The Pacific Northwest (PNW) is known for its lush greenery, thanks to abundant winter rainfall. However, the region’s dry summers, with less than 7 inches of rain from May to September, pose challenges for maintaining a healthy lawn. Proper watering practices are essential to keep your lawn thriving, prevent drought stress, and conserve water. This blog explores how to water your lawn effectively in the PNW, including how to measure your sprinkler’s water output, why different irrigation systems require unique approaches, and the specific water needs for a vibrant lawn.
The Importance of Proper Watering
The PNW’s climate is characterized by wet winters and dry summers, with cities like Portland averaging less than 1 inch of rain in July and August. This feast-or-famine precipitation pattern means lawns rely on supplemental watering during the growing season to stay healthy. Proper watering offers several benefits:
Prevents Drought Stress: Adequate water keeps grass green and resilient, avoiding brown patches.
Promotes Deep Root Growth: Deep, infrequent watering encourages roots to grow deeper, making lawns more drought-resistant.
Reduces Disease Risk: Overwatering can lead to fungal issues like moss or root rot, common in the PNW, while proper watering minimizes these risks.
Conserves Water: Efficient watering reduces waste, benefiting both your wallet and the environment.
Conversely, overwatering can cause shallow roots, increase disease susceptibility, and contribute to runoff, which harms local waterways. Understanding your lawn’s needs and your irrigation system’s capabilities is key to success.
Why You Shouldn’t Rely on Timers Alone
A common mistake is setting irrigation systems to run for a fixed time, such as 20 minutes, without knowing how much water is actually applied. Different irrigation systems—spray sprinklers, rotor sprinklers, drip systems, or soaker hoses—deliver water at varying rates due to factors like:
Nozzle Type: Spray heads may apply water faster but less evenly than rotors.
Water Pressure: Higher or lower pressure affects output.
System Age: Older systems may have leaks or clogged nozzles, reducing efficiency.
Zone Configuration: Different zones in your yard may have unique sprinkler setups.
Because of these variations, setting a timer without measuring output can lead to under- or overwatering. Instead, focus on delivering a specific amount of water, typically measured in inches per week, tailored to your lawn’s needs.
How to Measure Your Sprinkler’s Water Output
To water your lawn accurately, you need to measure how much water your sprinkler system applies. The “catch can test” is a simple, reliable method recommended by experts. Here’s how to do it:
Place Containers: Evenly space six or more straight-sided containers, such as tuna cans or cat food cans, across the area watered by your sprinkler. Ensure they cover the full spray pattern, including near and far from the sprinkler heads.
Run Sprinklers: Turn on your sprinklers and let them run for 20 minutes.
Measure Water: Use a ruler to measure the depth of water in each container (in inches or millimeters). Record each measurement.
Calculate Average: Add the measurements from all containers and divide by the number of containers to find the average depth applied in 20 minutes.
Determine Hourly Rate: Multiply the average depth by 3 (since 20 minutes is one-third of an hour) to estimate the inches of water applied per hour. Round to the nearest half-inch.
Example Calculation:
Container Water Depth (inches)
1 - 0.6
2 - 0.5
3 - 0.7
4 - 0.4
5 - 0.6
6 - 0.5
Total depth: 0.6 + 0.5 + 0.7 + 0.4 + 0.6 + 0.5 = 3.3 inches
Average depth: 3.3 ÷ 6 = 0.55 inches in 20 minutes
Hourly rate: 0.55 × 3 = 1.65 inches per hour
If your lawn needs 1 inch of water, you’d run this system for approximately 36 minutes (1 ÷ 1.65 × 60). Perform this test for each irrigation zone, as outputs may vary.
Tips:
Check for uneven distribution (e.g., if some cans have significantly less water). This may indicate clogged nozzles or poor sprinkler coverage, which should be fixed.
Repeat the test periodically, as system performance can change over time.
Water Requirements for PNW Lawns
Research indicates that lawns in the PNW, typically composed of cool-season grasses like Kentucky bluegrass, perennial ryegrass, tall fescues, or fine fescues, require approximately 1 to 1.5 inches of water per week during the growing season (spring through fall). This amount ensures healthy growth without overwatering. Key considerations include:
Hot, Dry Weather: During extended dry spells or heat waves, water needs may increase to 2 inches per week to prevent drought stress.
Cool or Wet Periods: Reduce watering during rainy or cooler weather, as natural rainfall may suffice.
Grass Type: Most PNW lawns use cool-season grasses, which have similar water needs. However, drought-tolerant varieties like fine fescues may require slightly less.
Soil Type: Clay soils retain water longer, while sandy soils drain quickly, affecting watering frequency.
Lawn Age: Established lawns need deep watering 2–3 times per week, while newly seeded or sodded lawns require more frequent, lighter watering until established.
For example, Levy's Lawns and Landscaping recommends 1–1.5 inches weekly, increasing to 2 inches during hot weather. Swansons Nursery advises ensuring lawns receive 1 inch weekly through rain or irrigation, while LawnStarter notes that some sunnier PNW areas may need up to 2 inches in summer.
Dormancy Option: In the PNW, letting your lawn go dormant during dry summer months is a water-saving strategy. If you choose this, water about 1 inch per month to keep roots alive, as the grass will recover when rains return.
Best Practices for Watering Your Lawn
To maximize the effectiveness of your watering and maintain a healthy lawn, follow these research-backed practices:
Water Deeply and Infrequently: Deep watering encourages roots to grow deeper, improving drought resistance. Aim for 1–1.5 inches per session, typically 2–3 times per week for established lawns.
Choose the Right Time: Water early in the morning (before 10 a.m.) or late evening (after 6 p.m.) to minimize evaporation and ensure water reaches the roots. Avoid midday watering, as much of the water is lost to heat.
Apply Mulch: Adding a 1-inch layer of organic mulch around trees, shrubs, and garden beds helps retain soil moisture and keeps soil cooler, reducing overall water needs.
Monitor Weather Conditions: Adjust your watering based on rainfall and temperature. Use a rain gauge to track natural precipitation and reduce irrigation after significant rain.
Check Soil Drainage: Ensure your lawn has proper drainage to prevent waterlogging, which can harm roots. Fix low spots where water pools by leveling or replanting with groundcovers.
Use Water-Wise Grasses: Consider planting drought-tolerant grasses like fine fescues or tall fescues, which require less water, as recommended by the Turfgrass Water Conservation Alliance.
Avoid Common Mistakes:
Overwatering: Leads to shallow roots, fungal diseases, and wasted water. Check soil moisture by inserting a finger 2 inches into the soil; if it’s moist, skip watering.
Relying on Timers: As noted, timers don’t account for system variability. Use the catch can test to set accurate schedules.
Watering Too Frequently: Shallow, frequent watering weakens lawns. Stick to deep, infrequent sessions.
Tailoring to Your Irrigation System
Every irrigation system is unique, and understanding its output is critical for efficient watering. Here’s how different systems vary:
Spray Sprinklers: Deliver water quickly but may be less uniform, requiring careful measurement to ensure even coverage.
Rotor Sprinklers: Apply water more slowly and evenly, often needing longer run times but providing better distribution.
Drip Systems: Deliver water directly to roots, ideal for gardens but less common for lawns. They require less frequent watering due to minimal evaporation.
Soaker Hoses: Provide slow, consistent moisture but may need longer run times to achieve 1 inch of water.
Because of these differences, you must measure each system’s output using the catch can test and adjust run times accordingly. For example, a spray sprinkler might apply 1 inch in 30 minutes, while a rotor might take 45 minutes. Regular maintenance, such as checking for clogged nozzles or leaks, ensures consistent performance.
Conclusion
Maintaining a thriving lawn in the Pacific Northwest requires a thoughtful watering approach tailored to the region’s dry summers and your specific irrigation system. By measuring your sprinkler’s output with the catch can test, you can deliver the recommended 1–1.5 inches of water per week, adjusting for weather and lawn conditions. Water deeply and infrequently, choose optimal times like early morning, and use mulch to conserve moisture. These practices not only keep your lawn lush and healthy but also contribute to water conservation in our beautiful region. Whether you’re nurturing a new lawn or maintaining an established one, understanding your system and your lawn’s needs is the key to success. Contact us today for a FREE ESTIMATE.