Growing plants in a coco coir medium requires a different approach than traditional gardening. The direct answer is that you should feed nutrients with every watering when using coco coir. This constant feeding strategy is necessary because coco coir is an inert substrate that functions more like a hydroponic medium than a soil blend. This ensures plants receive a steady supply of nutrition for consistent, robust growth.
The Reason for Constant Feeding in Coco Coir
Coco coir is derived from coconut husks and is considered inert, meaning it contains almost no inherent nutrients for plants. Unlike soil, which acts as a nutrient bank, coco coir offers no such reserve. This lack of a nutrient buffer means all necessary nutrition must be supplied directly through the water, making every irrigation an opportunity to feed.
The physical properties of coco coir further mandate this constant feeding schedule. It is highly porous with excellent drainage and aeration, which prevents root disease and promotes rapid growth. However, the nutrient solution flushes through the medium quickly. Consequently, nutrients not immediately taken up by the plant are rapidly washed away, requiring frequent replenishment.
The medium’s Cation Exchange Capacity (CEC) also plays a part in this feeding requirement. CEC is the ability of a medium to hold onto positively charged nutrient ions, such as calcium, magnesium, and potassium. While coco coir has a high CEC, it forms strong bonds with specific ions like potassium, often at the expense of calcium and magnesium. This dynamic easily destabilizes the root zone’s nutrient balance, necessitating a continuous supply of a balanced nutrient solution.
Practical Steps for Implementing the Feed Schedule
Treating coco coir like a hybrid hydroponic system requires careful measurement to ensure correct nutrient strength at every feeding. Growers measure the Electrical Conductivity (EC) or Parts Per Million (PPM) of the nutrient solution before application. This measurement indicates the total concentration of dissolved mineral salts in the water, which correlates directly to the available nutrition.
The goal is to maintain a consistent EC in the root zone, which produces the best plant growth by reducing stress from fluctuating nutrient levels. The most important technique for managing salt levels in coco coir is to feed until significant runoff is achieved from the bottom of the container. This runoff should typically be between 15% and 20% of the total volume of nutrient solution applied.
This generous runoff is essential because it actively flushes out accumulating mineral salts that the plant did not consume, preventing harmful salt buildup. Without sufficient runoff, water evaporates, but mineral salts remain, causing the root zone EC to spike and potentially leading to nutrient lockout or toxicity. The runoff process effectively resets the root zone with each irrigation, making a separate “plain water flush” only an occasional necessity, not a routine part of the schedule.
Managing pH and Essential Nutrient Requirements
Two specialized requirements are necessary for successful cultivation in coco coir, beginning with the precise management of the nutrient solution’s pH. The ideal pH range for maximum nutrient uptake is slightly acidic, typically ranging from 5.5 to 6.5. Maintaining the solution within this narrow window ensures that all macro and micronutrients remain soluble and available for absorption.
This target pH range is generally lower than what is used in traditional soil mediums. Therefore, monitoring the nutrient solution pH with a meter and adjusting it with pH-up or pH-down solutions is mandatory. If the pH drifts too high or too low, certain elements will become locked out, resulting in deficiency symptoms.
The second specialized requirement involves supplementing the feed solution with Calcium (Ca) and Magnesium (Mg), often using a product known as “Cal-Mag.” Coco coir’s natural cation exchange sites have a strong affinity for these two elements, chemically binding to them and making them temporarily unavailable. Growers must manually add extra Ca and Mg to the nutrient solution to saturate these binding sites in the coco. This ensures the plant can access the necessary amounts of these elements for healthy growth.