- Quality Growing Media
- Quality Potting Techniques
- Quality Watering Techniques
Quality Watering Techniques
If you are not familiar with the physical properties of water such as cohesion, adhesion, capillary action, and surface tension, I would recommend that you have a look at our "water property" page first. It also has excellent links to external articles.
Container Capacity
When a growing media is first watered, the pore spaces all fill with water, saturating the media and excluding air entirely. This is referred to as the saturation point, or the container capacity. This is the amount of water the pot can hold without puddles forming on the surface of the growing media.
Field Capacity
Once the pot has been filled, the gravitational forces will cause the media to drain excess water, pulling air into the media from outside. Once the pot has drained completely, the amount of water left in the pot is called field capacity, e.g. the amount of water the media is capable of holding.
Unavailable Water and Wilting Point
Not all of the field capacity water is available to the plants, however. Some pore spaces are so small that the water molecules will bond very strongly with the solid particles, and with other water molecules. When the roots can extract no more water, the remaining water in the growing media is said to be unavailable water, and the plants reach their wilting point. The media may still be wet. This is especially true for fine textured media like coconut coir and peat moss sphagnum. The only way to make water available to the plants again, is to wet the media back to field capacity.
PAW - Plant Available Water Capacity
The difference between field capacity and the wilting point is also called the PAW capacity, or Plant Available Water capacity, e.g. the amount of water physically available for plant uptake.
How often Should You Water?
When to water depends on many factors: the size of the pot, how fast the plant removes water, and by how much PAW water is available (a function of the growing media and the potting techniques).
The ideal scenario is one, where the media dries relatively quickly.
This allows the gardener to water again which pulls new air into the media, make dissolved fertilizers available, and it keeps disease pressure at bay.
Not all home growers are equally thrilled about the prospect of having to water several times per day, and a suitable compromise may have to be found, but as a general guideline, the faster the growing media dries, and the more often you water, the better off the plants are.
