Simple question. Not a simple answer. The complexity of the answer stems from the fact that the conditions of each landscape make each situation unique. Desert-friendly landscaping obviously requires a lot less water than the lush landscapes of Florida. But even within moderate climates, the amount of water shrubs require is dependent on the local climate, weather, soil conditions, and various other factors.   

The amount and frequency of watering depends on the root system of your plants. Shrubs and trees – known as woody plants - have the potential to grow deeper root systems than flowers which means they draw water from a larger volume of soil. In general, if you receive a good rain every week or 10 days, these woody plants are probably getting the water they need. They thrive with a deep watering with less frequency than most flowers.

The exception to this need for “more water less often” rule occurs if soil in your planting beds is compacted or if your plants are planted too deeply. If either of these factors is at work, the roots will only grow near the surface of the soil so they won’t get the oxygen they need to absorb water efficiently. This commonly happens in California where soils must be heavily compacted to protect buildings from earthquake damage. When plants are shallow-rooted they will need more frequent light irrigation just like the lawn.

How to Water Shrubs

The most efficient way to water woody shrubs is to apply water slowly to the soil allowing it to penetrate deeply to rewet the entire root system without running off. This can be done by repeatedly moving a slow flowing hose from bed to bed or by using a drip irrigation system that allows water to leak gradually along the entire length of the irrigation tubing. It is important that the water reaches the plants roots. It is unnecessary and wasteful to water deeper than the plant’s root zone.

If you are using an irrigation system, it is worth noting that woody shrubs need to be watered separately from shallow rooted plants and thus need to be on a different irrigation valve than lawns or flowers.

How to Determine the Right Amount of Water

The best way to gauge the amount of water you need is by checking the soils around your plants. Insert a garden trowel or even a long screw driver into the ground near the roots of your plants. If you cannot easily penetrate the ground 3-4”, you likely need to water.

With a little practice and some trial and error, you will be able to maintain the proper moisture balance to ensure your shrubs get the water they need to thrive in your landscape.

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