Cannabis Overfertilization: The Killer of Indoor Grows that is So Often Missed
Cannabis cultivation has exploded in complexity as growers seek to maximize their yields, however, the biggest mistake growers make is not underfeeding, in fact it is the opposite. There are more cannabis plants that die from overfertilization than from pests, diseases, and environmental stress combined. And, it is the least understood point of failure among growers.
The Nutrient Paradox
Cannabis evolved in nutrient-challenged soils which provided them with all the uptake efficiency they needed, but that efficiency is overwhelmed with modern hydroponic solutions. When EC levels exceed 1.8-2.2, cannabis plants automatically enter survival mode by shutting down photosynthesis and preventing damage to their cells. The beautiful irony: This is the threshold all professional nutrient suppliers consider when feeding instructions guarantee toxicity to the plant.
Recognizing the Silent Killer
The signs of overfertilization do not resemble what is outlined in the books or journals on nutrient burn. The early warning signs of overfertilization include:
- Dark and waxy leaves, which feel thick and brittle
• Interveinal chlorosis starting from the tips of the leaves and working inward
• Stunted vertical growth in spite of feeding aggressively through the vegetative stage
• Browning roots and limited branching patterns in hydroponic plants
When the plant reaches toxic thresholds, it experiences a cascading failure: since it is experiencing nutrient lockout, the plant then experiences deficiency symptoms, leading the grower to intensify feeding and ultimately leading to the death of the plant.
The Lockout Effect
Excess nutrients create ionic competition at uptake sites in the roots. High nitrogen content inhibits uptake of calcium leading to what appears to be calcium deficiency. It gets worse, overdosing on phosphorus prevents iron absorption, which appears as iron chlorosis.
Salt Accumulation: The Long Game
With soil grows, a long-term accumulation of salts from repeat overfertilization will exist in the plant medium, leaving salt accretion to persist through growing cycles. The grow medium has to be changed out completely, or the grower has to flush large quantities of water through the medium.
Recovery Strategies
The immediate flushing method involves aggressive flushing with pH water until the runoff reads below 1.0 EC. When soil is involved, after flushing, inoculate the medium with bacteria to re-establish microbial biology profiles. In hydroponic systems, change the reservoir immediately, and reduce feeding concentrations until the plant recovers.
For long-term recovery from over-fertilization, the grower’s proper feeding method is to feed the tissue at only 60% concentration of what the manufacturer recommends and to continually monitor plant response. Cannabis does better under nutritional stress than through abundance.
The Economic Effect of Less
Over-fertilization is double trouble for growers. The grower wastes expensive nutrients, and the kilos of cannabis require more work at harvest resulting in low quality. Properly fed cannabis will always provide better terpene profiles and higher cannabinoid concentrations than overfed plants. It is possible that less equals more in cultivation.
Finally, master growers remind us that the cannabis plant wants to survive, not be over-mothered. The plant’s ability to survive becomes the grower’s best asset once they stop force-feeding it to success.