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Plant Selection


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Efficiently watering plants

The goal is to have an irrigation system that maximizes efficiency by watering the right amount, at the right frequency, to the right place, at the right time. 

  • The amount is determined by the size of the plants in the hydrozone. The entire root ball area should be wet. Low and very-low use plants require less water overall, because they need less frequent irrigation. However, they still require their root ball to be soaked when they are watered.
  • The frequency will be influenced by the ability of water to move through the soil and the water needs of the plants. For low water use plants, it is usually once every three weeks, for very-low plants, a few times per summer. All soils must have time between watering to allow water to drain and oxygen to reach roots. Clay soils will hold water for even longer, so frequency will be reduced to allow them to drain.
  • The place is to the root zone where runoff and evaporation can be minimized. Larger plants will have larger root zones and may require a larger irrigated area. It is also beneficial to water deep. This helps to promote deep, drought-tolerant root growth.
  • The right time is usually between 2:00 a.m. and 6:00 a.m. This will reduce evaporation, but still prevent conditions that are conducive to pest and disease growth. Irrigation should also be adjusted according to weather conditions. Often landscapes won’t need any winter irrigation at all. 

A smart irrigation controller is highly recommended. Once set up, it can automatically adjust irrigation seasonally, increasing efficiency and paying for itself in water savings. Look for one with the EPA WaterSense label.

Compatible, complimentary plant communities can be established by grouping plants that have similar water needs into hydro-zones. When possible, re-use existing irrigation systems and retrofit them for increased efficiency. 


Here are a few irrigation guidelines:

  • The irrigation system should deliver water efficiently, with a minimum of waste or overspray on adjoining areas.
  • The system shall be designed to deliver the appropriate amounts of water to each hydrozone. Automatic irrigation controllers and separate control valves can provide for varying irrigation needs.
  • The system should be installed and tested prior to plant installation. 
  • If necessary, pressure reducers should be used to eliminate misting or operation outside of manufacturer recommended pressure.
  • Drip emitters are recommended for trees and shrubs.
  • Manual shut-off valves are recommended. Such valves should be situated as close as possible to the point of connection of the water supply to minimize water loss in case of an emergency, such as water line break, or routine repair.
  • Water conserving tools such as soil moisture-sensing devices or rain-sensing override devices should be used.
  • For larger installations, reclaimed water should be used where available and feasible.
  • Water early to prevent moisture loss and avoid disease problems.
  • Lower expectations during mid-summer and apply only enough water to keep the lawn alive but not lush, realizing it will green up again in fall.
  • Water moves slowly through clay soil types. When compared to sandy soils, clay soils require a lower drip rate running over a longer period time to apply the same amount of water.
  • Water moves quickly through sandy soils, so they require shorter, more frequent watering.​
  • Younger plants require more frequent watering as their root systems are not yet fully established. Inversely, fully established plants can require less water.

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