How often should you feed and water your plants?
When growing plants in a drain-to-waste setup and using a nutrient solution to deliver the plant nutrients, it is recommended that you feed with every watering. Many growers follow feeding and watering patterns in which they will feed one day and then use only water the next day (and similar variations) but we recommend against this schedule as it causes plant stress.
How often you should water the plants will depend on several factors including the size of containers used (smaller pots = more frequent watering), and the grow room temperature and humidity. As a rule of thumb, you should start by watering once per day, and observing the moisture of the coco in the pots for a few days. If you have especially large containers (which won’t dry out as fast as small pots) you may be able to get away with watering only every other day. Additionally, with each individual watering remember to water until you get a generous amount of runoff (10-20%).
Why shouldn’t you dry your grow media?
We don’t recommend letting the coco dry completely between irrigations. The plants respond better if you provide a constant level of moisture. If your substrate mixture contains a decent amount of perlite (25%) which helps the mix drain, overwatering shouldn’t be too much of a threat, so don’t be afraid to water on days even when the coco has only slightly dried. It is important to note that this “back-and-forth” between moist and dry conditions is very stressful on plant roots. Drying negatively impacts beneficial microbe populations in and around the root zone and creates a greater chance for harmful organisms to take over.
Why do we recommend feeding with every watering in coir based media?
Cation exchange capacity (CEC) is a property of soil and soilless media which directly affects nutrient availability. Growers generally use the “water/feed/water/feed” schedule in soil/peat based media mostly because soil cannot hold a lot of provided nutrients and thus salt tends to build up in the grow media. In comparison, because coir’s ability to hold and exchange nutrients with the plant is much greater than most soils, the buildup of salt is reduced in the coir based media.
Therefore, by feeding with the nutrient solution at every watering, you can maintain relatively uniform chemical conditions at the root zone. Maintaining appropriate levels of dissolved solutes at the root zone (by following application rates listed on the feed sheet) will create an osmotic gradient between the roots and coco. Having dissolved solutes in the root zone technically causes the water to enter the plant at a slower rate, which may sound like a bad thing, but ultimately results in the plant having to “try harder” to overcome the gradient.
Here is how it works:
- Applying dissolved solutes (i.e. nutrient solution) to the coco holding the roots will cause less water to enter the plant, because water favors moving towards solutes.
- The plant will then “compete” by producing its own solutes (like sugars and others) inside the roots, causing the solute concentration inside the plant to increase.
- Water will then continue to flow into the plant because the plant had to produce these extra solutes, and because water uptake has somewhat decreased.
- The concentration of these solutes is much greater in the harvestable end-product (these solutes being desirable things like sugars, aromatic compounds, essential oils, etc.), and ultimately the harvested fruits/flowers are more nutritionally dense, have stronger flavors and aromas and generally higher quality.
- In response to a constant presence of solute/nutrient/salt concentrations around the root zone, plants will synthesize compounds within themselves (often compounds, we growers desire, like nutrients etc.) as a way of “competing” with the soil for water—all to the benefit of the grower, as the harvested end product will end up with a higher concentration of beneficial compounds.
When a “feeding with every watering” schedule is applied (continuously feeding and applying nutrients), the osmotic gradient will continue to exist and the plant will keep producing sugars and other products.
However, when a “water/feed/water/feed” alternate type of schedule is applied, the nutrient concentration in the coco is always changing, bouncing back and forth between high in nutrients on the day of feeding and then being very low the following day. This oscillation between high and low nutrient concentration is stressful on the plants, but is certainly not catastrophic and many growers continue to use the “water/feed/water/feed” method without encountering too many problems. We simply recommend feeding with every watering as the best method to obtain higher end-product quality.