Nutrient burn is leaf damage from excess total salts in the root zone. As EC climbs, water uptake slows, and salts build up at the leaf tips and edges where water evaporates. The tips yellow, then turn brown and crisp, and the damage creeps inward along the margins. It is a general salt effect, not a single-element toxicity.
In practice
Typical triggers are feeding above the plant's tolerance, letting a coco or rockwool slab dry back hard so EC concentrates, skipping runoff in containers, or stacking additives on a full-strength base. Check runoff EC against input EC: runoff much higher than input means salts are accumulating. Lower the feed strength or water to runoff. In serious build-up, a root-zone flush to wash salts out of the medium is the valid fix. A slight tip burn in late flower on heavily fed plants is common and usually harmless.
Don't confuse with
- Heat or light burn: bleaching or crisping at the top of the canopy closest to the lamp.
- Potassium deficiency: margin burn on older leaves with yellowing first.
- Chloride or boron toxicity: specific elements, often from water.
Myth check
A root-zone flush treats the medium, not the plant, and is not a pre-harvest ritual. See the flush debate.
The root zone is the volume of medium or solution where a plant's roots live, including its water, air, temperature, pH, EC and microbes.EC (electrical conductivity) measures how well a solution conducts electricity, a proxy for total dissolved salts; growers read it in mS/cm to gauge nutrient strength.Nutrient toxicity is damage from an excess of an element in the plant, either directly or by blocking uptake of others; boron, manganese, copper and chloride are common culprits.Runoff is the water or nutrient solution that drains out of the bottom of a container after irrigation; growers test it to see what is happening in the root zone.Input EC is the electrical conductivity of the nutrient solution going into the pot or system, in mS/cm, including the base EC of the source water.Watering to runoff means applying enough water or solution that some drains from the bottom of the container, typically 10-20% of the volume applied.Running a large volume of low-EC water or mild solution through the medium to wash out accumulated salts; it treats the medium, not the plant, and suits any stage.Potassium (K) is a mobile macronutrient that controls water balance, stomata and enzyme activity; deficiency scorches the edges of older leaves.A feed chart is a manufacturer's or grower's schedule of nutrient doses by week or stage; treat it as a ceiling to test against, not a rule.Ppm of an element means milligrams of that element per litre of solution (mg/L), the unit nutrient recipes use; it is not the ppm shown on an EC meter.A nutrient deficiency is a shortage of an essential element in the plant tissue, causing characteristic symptoms; the cause is often pH or uptake rather than an empty feed.
