Back when I first started growing cannabis, my main concern was to give my plants the right amount of macronutrients, water, and light. But as I improved as a grower, I learned that dialing in the micronutrients was equally as important, and unless I became a master at understanding how each macro- and micro-nutrient played a role in plant development, I would have never become the grower that I am today.
One of the micros that play an important role in plant development is zinc (Zn) and a zinc deficiency in cannabis plants can cause a multitude of problems. In this step-by-step guide, I will teach you how to spot, correct, and prevent a cannabis zinc deficiency before it knocks out your next harvest.
(Zn) Zinc: Utilized in chlorophyll production, respiration and nitrogen metabolism. Zinc helps cannabis plants withstand colder temperatures and breaks down carbohydrates into sugars.
Deficiency: Zinc deficiency results in small leaves with crinkled margins.
Toxicity: Excessive Zinc may also reduce the availability of Iron.
Micronutrient: Absorbed in small to minute quantities. They are generally less well known than the macronutrients since most plant foods don’t contain them.
What does zinc do for cannabis plants?
Unlike Nitrogen, Potassium, and Phosphorus, Zinc is a micronutrient that your cannabis plants need for protein synthesis, enzyme production, and the regulation of plant growth hormones (PGH).
Zinc is also important in the synthesis of chlorophyll and it helps with energy production in the plant so it’s easy to see how a deficiency can have a big impact on the plant and flowers.
How does a zinc deficiency affect the quality of cannabis plants?
Cannabis plants with zinc deficiency can suffer from a bunch of annoying issues that ultimately decrease the overall quality of your product.
Zinc deficiencies normally result in stunted growth, reduced yields, and poor flower development with larfy and airy buds that have low potency and terpene production. Essentially, it results in bunk weed…
So what are the symptoms of a zinc deficiency?
Nutrient deficiencies can be tricky because the early signs are usually similar between different deficiencies. Yellowing leaves and stunted growth is common among most of them.
But learning to recognize the small differences allows you to spot the early signs that indicate a zinc-specific deficiency. The three stages of a zinc deficiency and their common symptoms are the following:
The early stage of a zinc deficiency
- Interveinal chlorosis or interveinal yellowing (yellowing between the veins) on younger leaves
- Reduced leaf size where the new growth gets stunted and stops growing
- Leaf curling or distortion that is especially visible on the leaf edges
The progression of a zinc deficiency
- Necrosis (dead leaf tissue) browning on the tips and margins of leaves
- Stunted growth and reduced internode distance
- Delayed or abnormal flower development
The late stage of a zinc deficiency
- Severe leaf distortion and spreading necrosis
- Leaves start to turn complerely yellow and brown and ultimately fall off the plant
- Widespread stunting and reduced yields with low potency and terpene production
What causes a zinc deficiency and what are common misdiagnoses?
As discussed earlier, some of the symptoms of zinc deficiency resemble those of other nutrient deficiencies. Nitrogen deficiency for example, also results in yellowing and distortion of the leaves.
So to avoid a misdiagnosis, you will want to consider all the symptoms and environmental factors before starting to treat the plants.
You need to look at the following 4 potential causes before you jump to any conclusions.
- Low zinc levels in the soil – It may sound obvious but a lack of available zinc in the soil or hydroponic solution is the number one reason plants suffer from zinc deficiency. Tap water contains around 50% of the necessary zinc that your plants need to thrive. If you use RO water (reverse osmosis), you need to add zinc back into your nutrient mix since RO water is devoid of any nutrients.
- Incorrect pH levels that reduce zinc availability – If your soil (or other medium) has too high pH, it is common to experience a zinc deficiency so check the pH. Cannabis plants absorb zinc most efficiently when the growing medium has a pH between 6.0 and 7.0 (slightly lower for hydroponics 5.5-6.5).
- Competition with other nutrients – Overfeeding of plants can result in “nutrient lock” which interferes with zinc uptake resulting in a deficiency. For example, excessive Phosphorous will reduce the availability of zinc
- Root damage or disease – Damaged roots hurt the intake of nutrients and absorption of zinc.
How to fix a zinc deficiency in cannabis plants
The recovery time for cannabis plants that suffer from zinc deficiency depends on the severity of the deficiency and how quickly you address it. The parts of the plant that were damaged will not regain their health so the earlier in the cycle you catch a Zn deficiency the better. You will see how new growth gradually improves and the plant fully recovers if the deficiency is caught during veg.
To correct a cannabis zinc deficiency you need to address the underlying cause and provide the necessary nutrients and optimal conditions for your plants to recover.
Here’s a step-by-step guide on how to fix zinc deficiency in plants:
- Check and adjust the soil pH to ensure optimal zinc availability. Aim for a pH range of 6.0-6.5 for soil-grown plants and 5.5-6.0 for hydroponic systems. If the pH is off, the system needs to be flushed completely with clean pH water then you need to add a balanced nutrient mix back in.
- Add a zinc-containing fertilizer or supplement to the soil or nutrient solution. Don’t over do it, start with a low dose and increase as needed but remember that zinc is a micronutrient and is only needed in small amounts.
- Prevent nutrient lockout by maintaining balanced nutrient levels and avoiding over-fertilization. If you flushed the system, add a slightly lighter nutrient mix back into the medium.
- Ensure proper root health by providing adequate drainage and avoiding overwatering.
Once you have completed the steps above you should start seeing how new growth show signs of improvement within 7-10 days. Keep a close eye on your plants for the next couple of weeks to make sure that the issue doesn’t return.
How to Add Zinc to Soil Naturally
To add zinc to soil naturally, you can use organic sources such as kelp meal, alfalfa meal, or composted poultry manure. Regular tap water is a good source for zinc for beginner growers.
Use microbes to keep your plants thriving
Amplify is your secret weapon to succeed as a grower. With a diverse blend of highly concentrated and naturally occurring plant growth-promoting rhizobacteria, the microorganisms in Amplify help increase the uptake of nutrients and water while also helping to protect your plants’ rhizosphere (roots) from harmful pathogenic microbes.
Our full-spectrum microbial inoculant is up to 3X more effective than competing brands, proven to drastically improve your plant’s nutrient uptake throughout the grow, boosting yields, and helping your plants reach their full genetic expression.