If you are somewhat new to growing cannabis, you are probably aware of the main concerns, such as giving your plants the perfect blend of macronutrients (Nitrogen, Phosphorus, Potassium), water, and proper lighting. As you get more experienced, however, you will begin to recognize the importance of micronutrients and the crucial role they play in plant development. One micronutrient that is critical for plant development is zinc (Zn).

It is important to understand what zinc does for cannabis plants, how to recognize a deficiency, and how to correct it for healthy growth.

What Zinc Does for Cannabis Plants

Zinc is a necessary micronutrient that is critical for the growth and development of cannabis plants. Zinc is important to the overall health and strength of your plant, including the stalks, branches, stems, and leaves. It is also a crucial element in a particular growth hormone, auxin, and is necessary in many enzymes. Plants that lack the correct amount of auxin will experience stunted growth in the shoots and leaves. Zinc is also crucial for the production of chlorophyll.

Zinc is a micronutrient that is necessary for enzyme production, regulating plant growth hormones (PGH), and protein synthesis. One of the most important roles that zinc plays in cannabis plants is the production of energy; thus, a zinc deficiency has a huge negative impact on the development of your plant as a whole and bud production.


How a Zinc Deficiency Affects the Quality of Cannabis Plants

A deficiency of the micronutrient zinc can cause many problems for cannabis plants, and a multitude of issues will arise that impact the overall quality of your plant. Zinc deficiencies will normally cause stunted growth, poor bud development, and reduced yields. Buds will have less terpene production, lower potency, and will be less dense and somewhat airy. Recognizing a zinc deficiency early can help to correct the problem.

A plant that becomes deficient in zinc could be caused by leaves or buds getting tangled or knotted. A zinc deficiency is somewhat similar to a deficiency in iron or manganese, although zinc affects new growth, virtually causing motionless growth.

Symptoms of a Zinc Deficiency

It can be tricky to diagnose nutrient deficiencies as the symptoms are similar among various deficiencies. Stunted growth and yellowing leaves are typical among many symptoms of nutrient deficiencies. Knowing how to recognize the subtle differences will help you to identify early signs of zinc deficiency.

Symptoms of a zinc deficiency include:

  • Early stages:
    • Leaf distortion and curling, particularly on the edges
    • Smaller leaf sizes due to stunted, stopped growth
    • Interveinal yellowing, chlorosis, between the veins of younger leaves
  • Progression:
    • Abnormal or delayed bud development
    • Reduced distance of internodes due to stunted growth
    • Browning on the tips of leaves and leaf necrosis necrosis (dead leaves)
  • Late stages of zinc deficiency:
    • Extreme leaf distortion and widespread necrosis
    • Completely yellowing and browning of leaves until they fall off the plant entirely
    • Severely stunted growth with low terpene production, low potency, and reduced yields

Examine potential causes of a Zinc deficiency to help diagnose the problem:

  • Low levels of zinc in the soil – this is the number one reason for a zinc deficiency. Tap water has about 50% of the necessary levels of zinc needed for plants to thrive. If you are growing hydroponically or using reverse osmosis (RO) water, you need to add zinc to your solution.
  • Unbalanced pH – if your pH level is off, this will reduce zinc availability. Soil that has a high pH level may commonly exhibit signs of zinc deficiency. A pH level between 6.0 – 7.0 (5.5 – 6.5 for hydroponics) helps plants to absorb zinc the most efficiently.
  • Root disease or damage – roots that are damaged inhibit the intake and absorption of nutrients
  • Nutrient competition – nutrient lock as a result of overfeeding plants or excessive nutrients lock out the absorption of other nutrients, resulting in a deficiency. Too much phosphorus can reduce the uptake of zinc.

How to Correct a Zinc Deficiency

The severity of a zinc deficiency and the timeliness of addressing it directly impact the recovery time. The damaged parts of the plant will not recover, so the earlier you catch a zinc deficiency, the better. New growth will start to improve, and the plant will completely recover if the deficiency is treated during the vegetation stage. You must address the cause of the deficiency and provide optimal conditions and necessary nutrients to correct it for a plant to recover.

  • Check the pH – make sure your pH is in the optimal range for zinc availability (6.0 – 7.0, or 5.5 – 6.5 for hydro). You may need to flush your plants and start fresh with the correct pH level in your water and add back nutrients.
  • Add a zinc supplement – start with the low dose to avoid overdoing it, and add a zinc-containing fertilizer as needed. Only a small amount of micronutrients is needed.
  • Avoid nutrient lockout – don’t overdo it to prevent nutrient lockout. Start with a lighter mix if you have to flush the system entirely.
  • Ensure healthy roots – avoid overwatering and provide adequate drainage.

Zinc can be added to soil naturally through organic sources such as alfalfa meal, kelp meal, or composted poultry manure. Regular tap water is also a good source of zinc.

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