5 Zinc Toxicity Symptoms to Look Out for in Your Plants

Zinc Toxicity Symptoms
5 Zinc Toxicity Symptoms to Look Out for in Your Plants – Plantsheaven.com

If you are a farmer or even simply an avid gardener, you have spent time making sure your plants have proper nutrition, including proper amounts of zinc, and you have also probably dealt with zinc toxicity. Now, zinc is essential for plant development, as it plays an important role in a wide range of processes. However, it is possible for your plant to receive a toxic amount of zinc and become sick. 

Zinc is an essential micronutrient in plants, but like any other nutrient or substance in nature, too much of a good thing can quickly turn into a health problem. You will want to know the symptoms of zinc toxicity. These can include stunted plant growth and all kinds of leaf issues.

Keep reading to learn more about zinc toxicity symptoms and what to look out for so you can address these issues immediately.

See also: Treating Molybdenum Deficiency in Plants: Here’s How

Yellowing Leaves Can Mean Zinc Toxicity

Yellowing leaves, with regard to zinc toxicity, are caused by the high levels of zinc in the plant soil, hindering iron intake, which is necessary for plants to develop and grow properly. Just as you feel bad if you have an iron deficiency, plants also need iron to develop properly.

High levels of zinc can prevent your plants from taking in enough iron, which can lead to yellow leaves.

During zinc toxicity, the veins in the leaves begin to turn yellow because these are areas that carry chlorophyll. Chlorophyll makes plants green, but you will see yellow instead of the characteristic green when this area is damaged. The zinc toxicity and subsequent iron deficiency cause the leaves to begin yellowing. This phenomenon is known as chlorosis.

You can address zinc toxicities and yellow leaves by using a fertilizer with a heavy phosphorus content. The high-phosphorus fertilizer lowers overall zinc levels in the soil and can stabilize the soil somewhat, but do not push it too far, or you will end up dealing with a zinc deficiency instead.

  • Phosphorus causes zinc content in the soil to decrease.
  • Decreasing the zinc content can stabilize the overall zinc level for the plants.
  • Remember that yellowing can occur at high or low zinc levels, so be sure you know what is causing your yellowing leaves before taking action.
  • High zinc causes iron deficiency which causes yellowing and stunted growth.

Additionally, if you spray your plants with various products, check the zinc content, as you could be applying too much zinc to your plants.

Now, although fertilizers that contain phosphorus as an active ingredient can lower the overall zinc level in your soil, they can come in handy in this situation where zinc intake is too high.

See also: How To Deal With Too Much Iron In Your Garden’s Soil: A Guide

Yellow Leaves Are Also a Sign of Zinc Deficiency

Zinc toxicity can be caused by either a deficiency or a large surplus of zinc in the soil or fertilizer you use. In either case, the zinc levels need to be adjusted. In the case of toxically high levels of zinc, fertilizer with phosphorus effectively lowers the overall zinc levels and stabilizes the soil.

If your plants are showing signs of a zinc deficiency; yellow leaves, stunted growth, curled leaves, etc., then chelated zinc, which you work into the soil, or a kelp spray, will raise the zinc levels to a healthy point and save the plants, as long as symptoms are not too advanced.

While zinc deficiency is the opposite of zinc toxicity, if zinc drops to a level that is too low, it will still have a toxic effect, as leaves will be smaller or yellowed, and the plant itself may have stunted growth or simply not grow. Now, leaves will also be yellow with seasons, but they can also be a sign of zinc deficiency or toxicity.

The way to identify zinc deficiency through yellow leaves is to look at the bottom leaves; zinc deficiency and toxicity essentially kill the plant from the roots up. You will see evidence of this if the bottom leaves are yellowing first. 

Bronzed Leaves Are a Symptom of Zinc Toxicity

Bronzing of leaves occurs after the yellowing of the leaves, which means that this symptom occurs once the zinc toxicity has advanced to a more critical stage. It is still possible to save a plant from the stage of bronzed leaves, but it is more difficult to do so.  

Bronzing of leaves signifies tissue death because the bronzed areas of the leaves can no longer perform photosynthesis.

Bronzed leaves are also a sign of excessive amounts of phosphorus in the soil, which occurs when zinc levels are very low; both zinc and phosphorus essentially regulate each other. Bronzed leaves mean an imbalance between the zinc and phosphorus in the plant soil.

  • During this stage of zinc toxicity, the leaves will not bronze all over.
  • You will see bronze-colored or darker brown spots appearing randomly on the leaves.
  • This bronzing will occur in addition to the yellow leaves caused in the previous stage of zinc toxicity. 
  • Bronzing also occurs first on the plant’s lower leaves, advancing up the plant over time.

You can prevent the bronzing and yellowing of leaves by testing soil to ensure it has a safe level of zinc for the plants. If it does not, adjust the nutrients in the soil accordingly using fertilizer.

Remember, zinc is good for plants in the right amounts. The aim is to stick to the ideal range of zinc, around 15 to 60 parts per million.

See also: How to Lower Manganese Levels In Soil

Bronzed Leaves Also Signifies Zinc Deficiency

As bronzed leaves are an indicator of toxic levels of zinc in the soil or your plants, they also indicate that your plants are critically zinc deficient. Now, other deficiencies exhibit many of the same signs as zinc deficiency or toxicity, such as iron, phosphorus, and sulfur deficiencies, so you will need to test the soil to make sure.

The effect is much the same; the leaf begins to yellow between the veins due to chlorosis, and if left untreated, then the yellow areas of the leaf progress to bronzing.

They will also have a vaguely rough texture because tissue death is occurring. It is difficult to rescue a plant when it has progressed to this stage. 

Stunted Plant Growth is a Sign of Zinc Toxicity

Zinc is essential for proper plant growth and development. Too little zinc and the plant will not grow and develop properly, but too much zinc and the plant will become toxic.

This zinc toxicity will negatively impact plant growth, development, and crop yield, depending on the plant. As such, suspected zinc toxicity must be addressed as soon as possible to prevent damage.

You will also see zinc deficiency in the new leaves that a plant produces; they will be smaller and curled upward or distorted. Zinc deficiency will give the plant an overall rosebud look and poor bud development due to zinc deficiency or toxicity. Along with that, if the deficiency is severe, the plant may never be able to produce new leaves.

  • Toxic levels of zinc will stunt plant growth or kill it completely.
  • You can see these symptoms through curled-up leaves.
  • Zinc toxicity causes poor leaf and bud development in plants.

There is not necessarily an iron-clad way to identify stunted plant growth except to monitor your plants during the growing season and make sure the majority are a normal size depending on the type of plant.

If more than a few plants are exhibiting stunted growth signs, then you have a problem.

Additionally, you will need to have the soil tested or re-examine the types of fertilizer you use to determine if you have a zinc deficiency or zinc toxicity issue. This is because iron deficiency/toxicity, phosphorus toxicity, and sulfur toxicity problems can exhibit the same basic symptoms as zinc deficiency or zinc toxicity.

See also: How To Remove Aphids From Kale: A Quick Guide

Zinc is Necessary for Photosynthesis and Growth

Zinc is necessary for plants to be able to conduct photosynthesis, which aids in growth and plant health overall. Too little zinc and the plant will never grow to full size; too much and the plant will be stunted or potentially die off altogether.

Zinc deficiency and toxicity can inhibit photosynthesis and basically kill the plant from the roots up.

Basically, zinc helps the plant produce chlorophyll at the right levels, and when those levels are thrown out of balance, then health problems arise. A phenomenon called chlorosis occurs, where the leaf tissue between veins turns yellow, bronzes, and then dies. This usually begins at the roots and moves up the stalk of the plant. 

If you spray your plants with additives to help them grow and you see signs of zinc toxicity, then there may be too much zinc in the additives you use.

Plants will tolerate increased zinc levels, but only to a certain point; past that, you begin causing damage. This damage is reflected in reduced growth and possible plant death.

Zinc Toxicity Causes Dwarf Leaves

Dwarf leaves are severely stunted leaves that never reach full maturity, due to either a critical nutrient deficiency for a long period of time during the early stages of the leaves’ growth cycle or a toxic level of a mineral or nutrient that also hinders the growth of the leaves.

Zinc toxicity and deficiency can prevent leaves from growing to full maturity and, in some cases, produce these dwarf leaves. Zinc toxicity prevents leaves from maturing properly through the zinc levels blocking iron intake and other minerals, and zinc deficiency simply prevents growth by lacking an essential nutrient.

  • Dwarf leaves directly result from stunted plant growth caused by zinc toxicity.
  • Dwarf leaves are caused by a lack of nutrients stemming from zinc toxicity.

Dwarf leaves are usually thinner, narrower, and shorter than regular leaves, often no more than one to three centimeters in length, and once dwarf leaves are shown, the plant very rarely grows to full maturity, as the nutrient deficiency or toxicity levels will have taken their toll. However, if addressed immediately, this can usually be prevented.

While dwarf leaves are more often caused by zinc or other nutrient deficiencies, zinc toxicity can cause dwarf leaves as well. The symptoms are the same: stunted growth, very small leaves, and very little growth past that point. The other symptoms of yellowing and bronzed leaves will also present themselves.

See also: How To Keep Ants Off Strawberry Plants: Here’s How To Do It

Malformed Leaves are a Sign of Zinc Toxicity

Along with dwarf leaves, which are critically undersized due to a deficiency of nutrients, in this case, zinc, malformed leaves are victims of the same deficiency or toxicity symptoms. Both malformed and dwarf leaves directly result from zinc deficiency or toxicity because they are present in amounts that are too large or small.

When it comes to zinc toxicity and deficiencies, plants can generally heal from them if they are addressed immediately, but if you let them progress to the point where most of the plant leaves are deformed or dwarf leaves, there is little hope of saving the plant.

It is similar to human illness. When addressed early on, proper steps can be taken to reverse the damage. There is a point where the damage becomes irreversible, however.

Another sign of malformed leaves due to zinc deficiency is wavy leaves, which exhibit wavy margins and edges in essence. While some plants have wavy edges naturally, when it comes to food crops, wavy leaf edges can be both a sign of malformed leaves and zinc toxicity/deficiency.

You will also see symptoms of malformation at the base of the leaf. Look at the joint between the leaf and stem. On a healthy leaf, that will be even on both sides of the join, but on malformed leaves, one side of the join will be higher than the other. Some plants exhibit this naturally, but on food crops, this can mean zinc toxicity

See also: How To Get Rid Of Worms In Potted Plants: A Quick Guide

Zinc Toxicity Can Cause Death of Leaf Tissue

Zinc toxicity can also cause the death of leaf tissue if left unchecked. This is due to the toxicity slowly poisoning the plant through iron and other mineral deficiencies. Now, this can occur through either the soil has high levels of zinc due to low pH or applying fertilizer and other products containing high levels of zinc.

Zinc toxicity also causes the death of plant tissue through the death of the little veins that transport water throughout the plant, and overall the death of plant tissue throughout the entire plant if the levels are high enough.

First, growth is hindered, then the plant suffers health issues, then the zinc toxicity kills the plant if it is not addressed in a timely manner.

As with other symptoms of zinc toxicity, this can be prevented by ensuring zinc levels are normal. If zinc levels are too high, you can lower them with phosphorus heavy fertilizer, which raises the pH of the soil and lowers zinc levels. Nitrogen fertilizer also has the same effect.

  • Zinc toxicity can slow plant growth or kill the plant altogether.
  • It causes death by killing the water transportation veins in the plant.
  • You can prevent this by ensuring zinc levels in the soil are safe.
  • Safe zinc levels can be attained by spreading phosphorus fertilizer.

High or low zinc levels affecting your plants to this level are usually a result of imbalances in the soil, such as an excess of one nutrient and a deficiency of another. This is repeated in the plants.

Phosphorus fertilizer is useful for bringing down high zinc levels, and chelated zinc in the soil will help raise zinc levels to a healthy degree.

See also: Is Sulfur Good For The Garden? Pros & Cons Of Using It

Zinc Deficiency Also Causes Tissue Death

Zinc deficiency can also cause tissue death in plants because it is at the other end of the scale from zinc toxicity. Plants can outgrow zinc deficiency, but if the deficiency is at an extreme level, the plant is highly unlikely to survive, even with zinc content adjustments using fertilizer or kelp spray.

Tissue death due to zinc deficiency is usually in areas of chlorosis, where the plant is already yellowing due to zinc toxicity or deficiency being at an untreated extreme. Chlorosis is a sign that the plant has health issues due to nutrient deficiency or toxicity, and tissue death is simply that health problem running unchecked.

On the soil front, you can add chelated zinc to the soil, which helps raise zinc levels to a healthy point if the plants are deficient. You should also work compost and other organic matter into the soil, especially sandy soil, because it helps provide zinc and other nutrients that the plants may or may not be getting. 

Zinc deficiency is much more common than zinc toxicity, but either way, they have damaging effects on your plants that can kill them if not taken care of. However, if you monitor your plants closely and address any problems immediately, you will not have many zinc-related problems. 


Hello friends, I am Altiné. I am SO excited you are here! I am the guy behind Plantsheaven.com. Plants Heaven is a blog that shares information about preparing, creating, and maintaining gardens in and out of your home, regardless of where you live. My goal is to help you learn to love gardening and reap the benefits that come with it. I am still learning; therefore, the information I share on this site may not always be “expert” advice or information. But, I do my VERY best to make sure the information shared on this blog is both accurate and helpful.

Recent Posts