Tips on Tree Nursery Practices Part 1

Watering (The Art and Science of Watering)

Understanding the “Science of watering” begins with an understanding of container root medium water relations.  Concepts like container capacity and perched water table are very important in understanding the science of watering container plants.

Perched water table means that the container has “free water” at the bottom of the container right after watering, when drainage has occurred. This is “free water” because it is not held by the root medium.

Because of this perched water table, the water characteristic of the container’s root medium is as if the container were sitting in water with “free water” at the bottom of the container.

Understanding container capacity is also important to understanding the science    of watering. Container capacity means that when a container is watered, and drainage occurs without channeling of the water, the container is fully saturated.

At this point the container root medium holds all the water it can hold, and applying additional water will only result in additional drainage of water. Good container root media have both water- and air-filled pores at container capacity.

Poorly drained root media as those that contain little air-filled pores at container capacity. The science of container root medium is most often a balance between air-filled pores and water-filled pores.

A good root medium should hold enough water so it does not have to be watered every hour, yet it must have adequate air for root growth even at container capacity.

The art of watering is determining when plants need to be watered and applying water properly. Plants should be watered just before wilting or just before water stress occurs.

Watering properly requires that each pot reach container capacity at each watering. A very important principle in watering is:

Overwatering occurs when plants are watered too frequently, not by applying too much water at a single watering. When overwatering occurs, the plant will not make roots and existing roots will die.