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.
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.
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.
Irrigation can be managed by using drips, sprayers and manual irrigation hoses but it is important to use the following guidelines:
Plant, trees and shrubs need water but the amount changes over time, depending on the following factors:
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 then entire plant.