Watering is critical for plant survival, both during the establishment period and throughout the lifespan of the plant. Ideally, water should be applied early in the morning or late at night to avoid loss due to evaporation. The soil should be thoroughly soaked with minimal water applied to the leaves of plants, as this may encourage fungus or disease. Do not overwater. In New York City, it is recommended that plants receive approximately 1 inch of water per week in total, species and weather dependent. New trees require approximately 10 gallons of water per caliper inch weekly (for example, a 2.5 to 3 inch tree would require 25 to 30 gallons per week).
Water shall be applied slowly to ensure adequate, deep infiltration into the soil and minimal runoff. Watering bags affixed to the tree trunk provide an effective tool during establishment to ensure slow, consistent water infiltration on top of the root ball; however, these need to be removed at the end of the establishment period. During drought conditions, watering frequency may need to be increased. Watering must be carefully scheduled and adjusted based on weather.
Irrigation systems are encouraged where appropriate maintenance of the irrigation system can be provided. The system, when properly maintained, can reduce the need for manual maintenance by ensuring the most frequently required task is automated. Newer systems also provide remote monitoring and scheduling, automatic weather adjustment, and maintenance notifications if the system needs repair.
Design of the system is paramount, as systems should not spray water onto the roadway or walking areas. Drip irrigation is most efficient but prone to damage and breaks. Pop-up or spray heads may be preferred as long as they can be directed appropriately. In many cases, even if a full irrigation system cannot be accommodated, simply providing a water source via a hose-bib connection will significantly reduce maintenance costs.
All irrigation systems require yearly winterization and start-up maintenance. They also require appropriate backflow prevention, typically a reduced pressure zone or “RPZ” backflow device, and a water meter, which must be approved by DEP. The RPZ and meter will need to be carefully sited within the project area to minimize visual impact, as they are large and obtrusive. Providing an irrigation system or water source will impact plant selection, allowing a wider range of plants to be used, but only if maintenance for the irrigation system is also in place.