Zinc is a micronutrient absorbed as Zn2+. It is a cofactor for many enzymes and is needed for making the growth hormone auxin, which is why shortage shows as stunted, compressed growth. It is only moderately mobile in the plant.
In practice
Deficiency produces small, narrow, twisted or wrinkled new leaves, interveinal chlorosis near the tips and very short internodes ("rosetting"). High phosphorus and high pH both reduce zinc availability, so a heavy bloom-booster regime is a classic trigger. Hydro feeds usually carry somewhere around 0.1-0.5 mg/L (ppm) Znbeing reviewed. Zinc sulfate or a chelate supplies it; galvanised pipes and fittings can leach extra zinc.
Don't confuse with
- Heat or light stress: can also curl new growth, but without the short internodes.
- Broad or russet mites: twisted, glossy new growth with no nutrient pattern; check with a loupe.
- Manganese deficiency: mottling without the leaf distortion.
Myth check
Zinc problems in flower are often caused rather than cured by high-P additives. See bloom boosters and nutrient antagonism.
A micronutrient is an essential element plants need only in trace amounts, below a few mg/L: iron, manganese, zinc, copper, boron, molybdenum, chlorine and nickel.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.Node stacking describes short internodes, so nodes and bud sites sit close together along a stem, giving dense colas and a compact plant.pH measures how acidic or alkaline a solution is on a 0–14 scale; in growing it controls nutrient uptake, with soil best near 6.0–7.0 and hydro 5.5–6.5.Zinc sulfate (ZnSO4) is the standard soluble zinc salt for micronutrient mixes, about 22.7% Zn as the heptahydrate and 35.5% as the monohydrate.A chelate is a metal ion held by an organic molecule at several points, keeping micronutrients such as iron, zinc and manganese dissolved and available across a wider pH range.Aculops cannabicola, a microscopic eriophyid mite specific to cannabis that causes upward leaf curl, bronzing and dull, greasy-looking trichomes.Manganese (Mn) is a micronutrient that splits water in photosynthesis and activates many enzymes; low pH can raise it to toxic levels.Phosphorus (P) is a mobile macronutrient used in energy transfer (ATP), DNA and cell membranes; cannabis needs moderate amounts and gains nothing from excess.Nutrient antagonism is when an excess of one element reduces the uptake or use of another, such as high potassium suppressing magnesium and calcium.
