Problems with Plants
Iron (Fe) - immobile
Deficiency Common when the pH is above 6.5 and uncommon when the pH is below 6.5. Symptoms may appear during rapid growth or stressful times and disappear by themselves. First symptoms appear on smaller leaves as interveinal chlorosis where veins remain green and areas between veins turns yellow. Interveinal chlorosis starts at the opposite end of the leaf tip, the apex of the leaves attached by the petiole. Chlorosis becomes progressively acute. Leaves fall off in severe cases. Iron (Fe) deficiency is sometimes traced to an excess of copper.
New growth turns pale green, young leaves yellow in between veins starting at petiole
More leaves yellow and develop interveinal chlorosis
Larger leaves yellow and develop interveinal chlorosis
In acute cases, leaves develop necrosis and drop
Treat Iron deficiencies: Lower soil pH to 6.5 or less. Avoid fertilizers that contain excessive manganese and Zinc (Zn). Improve drainage and increase root zone temperature. Apply liquid chelated. Apply a complete balanced hydroponic formula. Organic sources include well-rotted cow, horse and chicken manure.
Toxicity: Excess Iron (Fe) is rare. High levels of Iron (Fe) do not damage cannabis, but can interfere with Phosphorus (P) uptake. An overdose causes leaves to turn bronze accompanied by small dark brown leaf spots. If Iron (Fe) chelate is over-applied, it will kill the plant in a few days.
Treat excess Iron (Fe) by leaching flushing plants heavily.
Sulfur (S) - immobile
Deficiency: Young leaves turn lime green to yellowish. As shortage progress leaves yellow interveinally and lack succulence. Veins remain green. Leaf stems, petioles, turn purple. Leaf tips can burn, darken and hook downward. According to Mauk of Canna Coco, in the Netherlands, "we have repeatedly noticed that the symptoms were most obvious in the older leaves". S deficiency resembles nitrogen deficiency. Acute deficiency causes elongated stems that become woody at the base. Most common when pH is to high or when excessive calcium is present and available.
Similar to nitrogen deficiency; older leaves turn pale green
Leaf stems turn purple. More leaves turn pale green
Acute: purple leaf stems and yellow leaves
Treat deficiency: Fertilize with hydroponic formula that contains S. Lower pH to 5.5 - 6. Add inorganic S that contains magnesium sulfate (Epsom Salts). Organic sources include well-rotted mushroom composts and most animal manure.
Toxicity: Causes no problems if the EC is relatively low. At high EC plants take up more "available" S, which blocks uptake of other nutrients. Excess symptoms include overall smaller plant and uniformly smaller dark green foliage. Leaf tips and margins burn when severe.
Treat Toxicity: Flush growing medium with mild complete fertilizer. Check pH of runoff solution. Correct input pH to 6.0. Flush a minimum of three times the volume of water for the volume of growing medium.
Zinc (ZN) - mobile Deficiency: Most common micronutrient found deficient. First younger leaves exhibit interveinal chlorosis. New leaves and growing tips develop small thin blades, contort and wrinkle. Leaf tips and later margins discolor and burn. Often confused with a lack of manganese or Fe, but when deficiency is severe, new leaf blades contort and dry out. New growth is stunted blower buds contort, turn crispy dry and are often hard. Interveinal chlorosis of young leaves New leaves develop thin wispy leaves Lead tips discolor turn dark and die back New growth contorts horizontally New bud and leaf growth stops Treat deficiency: Flush growing medium with a dilute complete fertilizer containing chelated trace elements including Zn, Fe and Mn. Or add a quality brand of a hydroponic micronutrient mix containing chelated trace elements. Toxicity: Zn is extremely toxic in excess. Severely toxic plants die quickly. Excess Zn interferes with Fe's ability to function properly and causes Fe deficiency. Manganese (Mn) - mobile Deficiency: Young leaves yellow between veins and veins remain green. Symptoms spread to older leaves. Dead spots develop on severely affected leaves before they fall off. Plant is stunted and maturation prolonged. Sever deficiency looks like a severe lack of Mg. Interveinal chlorosis of young leaves Interveinal chlorosis of progressively older leaves Dead spots develop on acutely affected leaves Overall growth is stunted Toxicity: Young and newer growth develop chlorotic dark orange to dark rusty brown mottling, first on young leaves before progressing to older leaves. Slow growth loss of vigor. Toxicity is compounded by low humidity. The additional transpiration causes more manganese to be drawn into foliage. Excess manganese causes a deficiency of Fe and Zn.