Proper watering of trees and plants

The Roots

The root system of a plant or tree is vitally important as it transfers water, oxygen, and minerals from the soil to the leaves. During the winter, roots store food to produce good growth in the spring. Roots also serve as an anchor against high winds.


Systems are comprised of perennial and mammalian roots. Together, these are typically found in the top 15 to 60cm of soil and rarely deepen to more than 1m. Perennial roots are large while mammalian roots are small, short and thin but form the largest, upper part of the system. To obtain oxygen and minerals, the mammalian roots grow upwards and laterally in the upper part of the soil and are their abundance is relative to the depth of the ground.

The root system occupies a large area under the ground, usually 2 to 4 times the radius of the landscape. Different types of soil affect the penetration of water, oxygen and minerals. Soil with a high capacity for holding water, such as clay, will hinder the spread of roots while light or sandy soil is typically dry, roots spread and deepen towards sources of water.

The Plants

New plants

Until new plantings are well established, irrigation beyond the diameter of the tree or plant is required while new roots grow and are established deeper and wider. It can take two years of more for the root system to expand and mature. The “root ball” or central group of roots dries faster than the peripheral system.


Mature plants

Once plants are mature, watering near the stem should be avoided because it is ineffective to deliver water to the entire root system and may encourage development of disease. The main area where roots absorb water is in the “drip line” region which is the area under the outer edge of the shrub or tree.

How to water

Irrigation can be managed by using drips, sprayers and manual irrigation hoses but it is important to use the following guidelines:

  • Water the area deeply and widely, at frequent intervals (depending on the plant).
  • Minerals and water are collected by the roots at a depth of 45 - 60 cm, so watering to this depth is essential.
  • Watering at intervals of 10 - 21 days is recommended, depending on the plant, soil type and season.
  • Avoid over-watering because this disrupts oxygen in the soil and suffocates the roots as well as causes rot and disease.
  • Evaluate the soil to determine water content and finalize irrigation intervals based on findings. 

Amount of water

Plant, trees and shrubs need water but the amount changes over time, depending on the following factors:

  • The age of the tree or shrub
  • Root damage: A mature tree or shrub with damaged roots will require more frequent irrigation to allow growth of new roots.
  • Season of the year: Hot, dry and humid weather in the summer will require increased irrigation because the moisture from rain is depleted.  

Other factors

  • Weather Conditions: In times of drought, the water in the soil runs out earlier, so a longer season of irrigation will be needed.
  • Plant type: Drought-resistant varieties will also benefit from additional irrigation in drought. Local trees, shrubs and plants will do well after they are established but varieties from different regions will require auxiliary bags in hot seasons to look their best.
  • Soil types: Soil types (heavy, sandy, clay, etc.) and depth, affect the water grip in it.
  • Irrigation spacing:  Heavy soils retain water for a long time so decreased irrigation is required compared with sandy soil which requires more irrigation to keep moisture in the ground. 

Signs of excessive watering

Camille (wilting)

  • The foliage at the bottom of the plant turns yellow.
  • The leaves fall downwards (may also occur in drought).
  • Leaves are soft to the touch ("rags") and not dry and crisp as in short supply.
  • Young yellow upper foliage has dark green arteries, a sign of iron deficiency that characterizes heavy soils.


  • Flowers show signs of decay
  • Fungi develops near the stem
  • Root rot

Signs of inadequate watering

Camille (Wilting)

  • The leaves slope downwards with leaves folding inward.
  • Leaf shedding and abundant flowering
  • Leaves lose their luster
  • Leaves become slightly translucent
  • On the lawn the foliage folds slightly and does not straighten after treading
  • In succulents the foliage becomes soft to the touch

Factors affecting irrigation

  • Exposure to sun and shade
  • Type of soil (heavy, sandy, clay, etc)
  • Type of plants
  • Ground cover
  • Seasons (Temperature)
  • Pruning
  • Fertilizer


Browning is caused by failure of roots to carry water upwards to the foliage which dries out and becomes discolored initially at the leaf tips then the entire plant.  


Final results:

  • Slow growth
  • Small leaves
  • Decrease in quantity and number of flowers and fruits
  • Vulnerable to pests and diseases