The Importance of Water

When we talk about the importance of newly planted trees and shrubs becoming “established” in the garden, we are referring to the development of a healthy root system. This root system is the basis for the plant’s top growth and long term health. And water is the key ingredient in developing that root system.  For the first two years of its life in your garden, the tree and its roots are particularly sensitive to water deficits. As the tree matures, its roots reach deeper into the ground and are able to tap water sources there. 

New shrubs and trees will require supplemental watering throughout the first growing season, right up to the onset of winter, and again in the second growing season. Water needs to be applied in the form of a gentle and deep soaking, down to the bottom and around the entire circumference of the root ball. Importantly, plants will require this watering at least once a week, and oftentimes twice a week in order to prevent any part of the root system from drying out.  

How much water a plant needs depends on its size. A small shrub will need 2-3 gallons of water each time it is watered. A larger shrub, 3-5 gallons. A small tree will need 5-8 gallons.  Mid-sized and larger trees, correspondingly more.


Water can be delivered in several different ways: 

  1. Leave a hose on a slow trickle at the base of the plant sufficient to soak the root mass. 
  2. Slowly pour large buckets of water around the plant, allowing each bucket full to soak into the soil. 
  3. Hook up a dripper hose on a timer which will relieve you of the burden of finding time in your busy schedule. 
  4. Know which of your perennials are more drought tolerant (ex. Sedum, Coneflower, Yarrow) and those which need regular watering to look their best. Using a watering can or a hose on a very gentle trickle applied at the base of the plant is the best way to apply water where it is needed most.  


Sedum are drought tolerant plants.


When and how much we water our plants is of course influenced by how much rain we receive. While it is tempting to skip your watering duties when we get a light afternoon shower, be mindful that a light shower is not likely to be enough to soak the depth of the root ball.  Knowing that established plants require at least an inch of water every week, it is helpful to keep an eye on your weather app or an old-fashioned rain gauge to track weekly totals. 


Two watering strategies that will not serve your plants well: 

  • Watering frequently but lightly does not benefit the tree or shrub as it encourages root development at the surface, making the roots particularly vulnerable to drying out in times of water deficit.  
  • Keeping a plant in soaking wet conditions day after day will deplete the oxygen in the soil, not a good thing for any life form! Hence the need for deep watering followed by a period in which the soil is allowed to dry out.  

Even as night time temperatures cool and the grass is moist with dew in the morning, it is important to keep up your program of supplemental watering until the ground freezes.

And remember, most plants prefer deep infrequent waterings to frequent shallow ones. See our planting guide for more information!