Zinc toxicity
Zinc toxicity; photo courtesy of USDA ARS

Zinc may be a micronutrient, but it is of vital importance to garden and field crops. Take a look at this list of roles:

  • Aiding in DNA transcription.
  • Activating enzymes that control growth.
  • Regulating carbon dioxide balance.
  • Regulating water balance.

Because zinc is used in seed production, as well, it is of particular importance in grain crops.

Natural Sources

Some soils naturally contain plenty of zinc. Kelp extract also tends to contain zinc.


Zinc levels may drop too low due to erosion or leaching caused by low organic matter levels. Cool soil temperatures, high pH, and high phosphorus levels tend to interfere with the ability of plants to take up whatever zinc is available. In high-yielding plants, this can be enough to trigger deficiency symptoms.

Symptoms of zinc deficiency in plants include:

  • Reduced shoot growth.
  • Short segments of stem between nodes.
  • Tiny leaves.
  • Fading of leaf color between veins.
  • Dead spots on leaves.

Correcting zinc deficiency starts with good soil care. Add organic matter as necessary to prevent erosion and leaching, then correct the pH to near neutral.

If your plants have experienced zinc deficiency before, consider planting later to give soil temperatures time to rise in the spring. Alternatively, till in any plant residues on top of the ground to allow faster warming.


Zinc is toxic to plants in all but the smallest quantities. Therefore, pollutants high in metal content, such as sewage sludge and deteriorating metal equipment, can easily cause a problem. Plants may absorb too much zinc when the soil is excessively acidic or when it contains excess magnesium.

This type of toxicity is not too common, but when it does occur notice the following (rather subtle) symptoms:

  • Stunted growth.
  • Unusually dark leaf color.
  • Reduced yield.

If zinc toxicity occurs, your best bet is to eliminate any sources of contamination and raise the pH to a near-neutral level.

Complete Series

Minerals in Plants

Minerals in Plants