A soaker hose is a porous tool designed to deliver water slowly and directly into the soil, offering an efficient method for irrigating shrubs. This technique promotes deep root growth by minimizing water loss from surface runoff and evaporation common with traditional sprinklers. Determining the correct run time is key to shrub health, ensuring the root zone is adequately moistened without waterlogging. Calculating the run time involves measuring the shrub’s water needs and the hose system’s output.
Determining Shrub Water Requirements
The goal of watering established shrubs is to saturate the primary root zone deeply, encouraging roots to grow downward. For most mature shrubs, feeder roots are concentrated in the top 12 to 18 inches of soil; this is the depth you should aim to moisten with each watering cycle. Watering to this depth promotes a deep, drought-resistant root system. Conversely, frequent, shallow watering causes roots to remain near the surface, making the plant vulnerable to heat and drought stress.
Soil type significantly influences water retention and irrigation frequency. Sandy soils drain quickly and require shorter, more frequent watering sessions because they hold less water. Clay soils absorb water slowly but retain it longer, necessitating less frequent but longer watering periods for deep penetration. For example, clay soil may need one deep watering per week, while sandy soil might require half the volume applied every three or four days.
Calibrating Your Soaker Hose System
Before calculating the run time, determine the actual application rate of your soaker hose setup, as output varies based on water pressure and hose length. Lay out the soaker hose exactly as it will be used for watering your shrubs. Installing a pressure regulator at the spigot is beneficial to maintain consistent output, as soaker hoses perform best at a low pressure, typically 10 to 12 pounds per square inch (PSI). Higher pressure causes uneven water distribution, leading to a “geyser” effect near the faucet and poor output at the end of the line.
To measure the output, place several straight-sided containers, such as tuna cans, along the length of the soaker hose near the shrubs’ drip lines. Turn the water on for a set period, such as 30 minutes, and measure the depth of the water collected using a ruler. Calculate the average depth collected, then convert this measurement to an hourly rate by multiplying the average depth by two. This provides the inches of water delivered per hour, translating the flow rate into a practical measure of application to the soil.
Calculating the Run Time
The final run time is determined by dividing the required water depth by your calibrated hose output rate. If a shrub requires one inch of water and your soaker hose output is half an inch per hour, the run time is two hours. This calculation provides a precise baseline duration for your watering session. The time required for the water to penetrate the full 12 to 18 inches of the root zone will vary based on your soil’s texture.
For example, if your shrub needs 1.5 inches of water and the soaker hose delivers 0.5 inches per hour, you must run the hose for three hours. Since the goal is deep, infrequent watering, this calculated time represents a single, complete irrigation cycle. The frequency of repeating this cycle depends on your soil’s ability to retain moisture and environmental conditions.
Adjusting Timing Based on Environmental Factors
The calculated run time must be adjusted to account for external variables. Prolonged periods of high heat and wind increase a shrub’s water demand due to higher rates of transpiration and evaporation, requiring a slightly longer run time or more frequent application. Conversely, during cooler, humid weather or following recent rainfall, reduce the frequency of watering to prevent saturation and maintain a healthy air-to-water ratio in the soil.
A shrub’s maturity also dictates adjustments. Newly planted shrubs need more frequent, slightly shorter applications to establish roots around the root ball. Established shrubs benefit from less frequent but deeper watering to sustain their mature root systems. Sloped areas may require the overall run time to be broken into two or more shorter intervals with rest periods. This allows water to soak in and prevents runoff, ensuring the water reaches the root zone.
Monitoring and Seasonal Fine-Tuning
Irrigation requires verification of the calculated run time by checking soil moisture. The simplest method is the “screwdriver test,” where you push a long, flat-bladed screwdriver or metal rod into the soil 24 hours after watering. The tool easily penetrates moist soil but stops abruptly when it hits dry soil, indicating the water penetration depth. For established shrubs, the screwdriver should penetrate at least 12 inches to confirm the water reached the primary root zone.
Fine-tune your watering schedule throughout the year based on seasonal changes. Increase the frequency of deep watering during the peak heat of summer and decrease it significantly in the fall and winter when plants are dormant. Watching for signs of stress is important: wilting leaves that recover at night suggest under-watering. Yellowing leaves and a constantly damp soil surface can indicate over-watering, requiring an adjustment to the run time or frequency.