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Fixing Common Cannabis Deficiencies

May 26, 2020
How & When to Feed Your Plants

Preventing and Fixing the Common Cannabis Nutrient Deficiencies

To provide the best yield possible, cannabis plants need a healthy, varied diet. With the information and tips in this guide, growers can minimize the risk of nutrient deficiencies and quickly resolve them if they occur. Whether you grow sativa weed seeds or indica weed seeds purchased online from our seedbank, or have another popular strain of marijuana seed that you’ve obtained from another grower, these tips should apply to all types of medical cannabis seeds and industrial hemp nutrition as well.

Why is Nutrition So Important to Cannabis Plants?

Just like people do, marijuana plants need a healthy diet that’s full of variety. They need nutrients in the right quantities to fulfill crucial physiological functions, and if there’s a deficiency in any area, growth and yield will be affected.

Fortunately, most cannabis plants like candy cream and the strawberry cheese strain do an excellent job of telling growers what they need. If a nutrient deficiency occurs, a plant may wilt, curl its leaves, or become discolored. With these signs, the cultivator can determine what the plant requires. Before we get into the prevention and resolution of various nutrient deficiencies, though, there are a few things you should consider.

Macro and Micronutrients

A macronutrient is a mineral that plants need in significant quantities. Macronutrients include potassium, phosphorus, and nitrogen. Just like protein, fats, and carbohydrates form the basis of the human diet, cannabis plants need the above minerals to perform crucial processes.

Micronutrients are elements in minerals used in smaller quantities, but that doesn’t make them any less important to the plants’ health and vitality. Micronutrients include boron, iron, sulfur, and zinc, among others. They’re best thought of as being like vitamins and minerals in our diet. We don’t require much, but a deficiency can cause serious problems.

Mobile and Immobile Nutrients

Distinguishing between immobile and mobile nutrients can help a cannabis cultivator diagnose deficiencies accurately. A mobile nutrient is a mineral that is carried throughout a plant to the parts that need it the most. For instance, the phosphorus in old fan leaves may be diverted toward new growth in the event of a deficiency. Therefore, these deficiencies may first be detected in old growth.

An immobile nutrient is held in place and the plant cannot redistribute it. For instance, if there’s a zinc deficiency, the signs will appear in new growth as the cannabis plant can’t divert its stored minerals.

Mobile nutrients include:

  • Nitrogen
  • Phosphorus
  • Potassium
  • Magnesium
  • Molybdenum

The following nutrients are immobile:

  • Calcium
  • Sulfur
  • Iron
  • Manganese
  • Zinc
  • Boron

Read on to learn how these nutrients, plus soil pH, can affect plant health.

Healthy pH is Crucial

A garden can have nutrient-rich soil, but the plants won’t be able to absorb those nutrients if the growth medium’s pH is incorrect. Cannabis plants do best at a pH of 6.0-6.5; anything above or below that will make it difficult for the plants’ roots to absorb crucial nutrients. This phenomenon is referred to as nutrient lockout, but routine system flushes can prevent it. Use a pH meter to measure levels frequently, and if necessary, change the pH of the soil with the following technique.

Go Organic

Developments in soil technology have demonstrated that the root zone or rhizosphere is teeming with life. In the root zone, an intricate network of microscopic life works in synergy with the roots. The soil requires the right balance of fungi and bacteria to degrade organic material and unlock nutrients for the plants to absorb.

Through composting, a grower can build living soil that prevents nutrient deficiencies and supports biodiversity within the root zone. With this practice, your soil will be full of the beneficial life that helps keep plants healthy and increases yields.

However, a grower can also take direct, short-term action. Spraying nutrients on the foliage is a quick fix when cannabis plants are running short. When nutrients are given in this manner, they bypass the roots and are taken in through the plants’ leaves.

Now that you’ve learned how to control soil pH with natural methods, let’s discuss how to stop and resolve nutrient deficiencies.

Prevention and Resolution of Nutrient Deficiencies in Cannabis Plants

Below you’ll find a list of the most common nutrient deficiencies encountered by cannabis cultivators, as well as tips on preventing them and fixing them if they arise.

  • Nitrogen is a mobile nutrient that plays a significant role in plant protein formation and photosynthesis. When your OG Kush plants have a nitrogen deficiency, their older leaves may turn yellow and fall off, with eventual widespread discoloration and diminished crop yields. Prevent a nitrogen deficiency by keeping the growth medium’s pH within the right range (6.0-6.5). Begin with a nutrient-rich soil mix, and compost to ensure the continued nutritional diversity of the growth medium. Mycorrhizae tend to encourage the growth of nitrogen-fixing bacteria, and they can be added to the soil to increase nitrogen levels.

Most organic fertilizers have enough nitrogen to resolve a deficiency. Manure, alfalfa, feather meal, and fish meal are all great choices for a cannabis garden. Check and adjust the soil’s pH as needed and consider applying compost tea to the foliage for a quick fix. Increase the nitrogen content of your compost by adding fresh cuttings, grass clippings, and kitchen scraps.

  • Phosphorus is another crucial micronutrient. Because it’s highly mobile, plants can divert the nutrient to the parts that need it. Phosphorus plays a key role in protein synthesis and photosynthesis, and it’s one of the building blocks of DNA. A phosphorus deficiency can appear as purplish or red stems, dry leaves, or brown spotted leaves. Prevent a deficiency by using soil that’s rich in organic material. Increase nutrient uptake rates with regular soil aeration and the use of mycorrhizal fungi. These beneficial microbes will turn insoluble phosphates into absorbable molecules.

Fix the deficiency by bringing the growth medium’s pH up to the high end of the normal range, as this makes it easier for plants to absorb phosphorus. Adding fish meal and worm castings to the soil may also help, as will the use of a high-phosphate organic fertilizer. Overwatering is a common problem, but it’s easily solved. Water the plants only when the top inch of the soil is dry. If possible, move the plants to a warm spot or put up a tarp to hold in heat. Cannabis plants find it difficult to absorb phosphorus in temperatures below 59 degrees Fahrenheit.

  • Potassium is the third macronutrient cannabis plants need for healthy growth. It regulates carbon dioxide absorption and aids in photosynthesis. This highly mobile nutrient assists in ATP (cellular energy) production. A potassium deficiency may appear as curled leaves, brown or yellow leaf edges and tips, and plant stretching. To prevent a deficiency, use fertilizers wisely. Feeding plants too often will cause a buildup of salt, which interrupts potassium absorption. Use kelp meal and hardwood ash in compost, and water plants carefully.

Once a deficiency has arisen, resolve it by flushing the growth medium. Next, measure the pH and adjust it to correct a potential nutrient lockout. Add some chicken manure to the soil and spray the foliage with an organic seaweed solution.

  • Calcium is crucial to the health of cannabis plants. It’s an immobile nutrient that holds the plants’ cell walls together. A deficiency can lead to the incorrect formation of young leaves and root tips. Prevent a deficiency by adding dolomitic lime to the growth medium and keeping the pH around 6.2. Boost the potency of your compost with eggshells and worm castings, which provide high levels of calcium and other nutrients.

Resolve a calcium deficiency with a calcium/magnesium supplement and regular pH monitoring. Finally, water your plants with a solution of one teaspoon of lime to four liters of water.

  • Sulfur is only required in small amounts, but this immobile nutrient is important because it’s used to form proteins and enzymes. A deficiency will appear as yellow new growth and discolored leaf undersides. Minimize the risk of a deficiency by adding manure to the compost pile. Bacteria and fungi help to release sulfur into the soil. Help them do their job by avoiding tilling and using mycorrhizae in potted gardens.

Fix a sulfur deficiency with Epsom salts. Add one or two teaspoons of salt to four liters of water and supplement the plants until the symptoms go away. Adjust the growth medium’s pH if necessary.

  • Magnesium is another immobile nutrient that plays a role in photosynthesis. This important mineral is present in chlorophyll molecules and it allows them to absorb sunlight. A magnesium deficiency will cause deformed lower growth, and leaves will dry out before turning yellow or brown. Prevent a deficiency by using dolomitic lime in the growth medium and by using manure-rich compost. Finally, ensure the proper pH balance.

Stop a magnesium deficiency by flushing the growth medium with 6.0 pH water if needed. Epsom salts are a rich source of magnesium; make a solution of one or two teaspoons of Epsom salts and four liters of water and apply it to your plants until the symptoms disappear.

  • Iron plays a role in the formation of chlorophyll. This crucial element also assists in enzyme and pigment formation. An immobile micronutrient, iron helps cannabis plants perform various energy formation and metabolism processes. If your plants are deficient in iron, their new growth will become a bright yellow. Prevent a deficiency by supplementing the soil with mycorrhizae. These beneficial organisms help to move iron through the root system and into the plants. Test the soil’s pH to eliminate the possibility of a nutrient lockout, and use seaweed, kitchen scraps, and chicken manure in the compost pile.

Fix an iron deficiency by keeping the growth medium’s pH in the appropriate range. Flush the medium and use an iron-containing supplement afterward. Use nitrogen fertilizer to reduce pH and make iron more readily absorbable.

  • Manganese gets little attention from growers, but this micronutrient plays a critical role in the plants’ physiology. Manganese assists in respiration, photosynthesis, nitrogen uptake, root cell growth, and more. When plants don’t get enough manganese, new growth will be discolored at the base. The discoloration may spread until the leaves develop brown spots. Prevent a deficiency by measuring the growth medium’s pH and keeping it within the right range so your plants can absorb the mineral. Strengthen your compost by adding cranberries, carrots, tomatoes, and pineapple.

A manganese deficiency can be cured by flushing the growth containers and pruning back growth that hasn’t recovered. Use a seaweed spray on the canopy of your indoor or outdoor cannabis crop.

  • Boron works with calcium to strengthen cell walls and assist in cell division. Cultivators value this nutrient as it helps with pollination. A boron deficiency will cause symptoms such as diminished fertility, poor growth, and short meristems. New growth may be misshapen, sugar leaves may wilt, and other leaves will become brown or yellow. To prevent a lack of boron, don’t let plants get too dry and avoid overfeeding. Use aerated, well-draining soil, and supplement the compost pile with bananas, broccoli, apples, chickpeas, and bananas.

Fix a deficiency by flushing the growth medium and keeping it within the appropriate pH range. Combine one teaspoon of boric acid with four liters of water and apply it to the affected plants.

  • Molybdenum isn’t as well-known as some other nutrients, but it helps to form essential enzymes that break nitrate down into nitrite and ammonia. Cannabis plants use ammonia to make vital amino acids, which are turned into proteins. If your plants are suffering from a molybdenum deficiency, their new growth may acquire a pinkish or reddish tinge at the edges. Fortunately, molybdenum deficiencies are very rare. Prevent them by keeping the growth medium’s pH between 6.0 and 6.5. Start a grow op with living compost and add raw nuts, grains, peas, and beans to the pile.

Resolve a molybdenum deficiency by flushing the growth medium and adjusting its pH as necessary. Spray affected areas with an organic seaweed solution and water the plants with compost tea containing worm castings.

  • Zinc is only needed in small doses, but when the plants don’t get enough, they’ll quickly fall ill. Zinc is essential in the formation of cell membranes, growth hormones, and proteins, and it also stabilizes RNA and DNA. When plants suffer from a deficiency, they may grow slower and new leaves will look yellow and wrinkled. Zinc deficiencies can be prevented by maintaining the soil’s pH. Increase the zinc level of your compost by adding squash and pumpkin scraps. Finally, beneficial fungi can assist in plants’ zinc uptake.

Once a zinc deficiency sets in, it can be cured by reducing the growth medium’s pH to the correct level. Don’t overwater your plants and apply a seaweed- or fish-based foliar spray to increase zinc levels quickly.

In Conclusion

Though cannabis plants only need some of these nutrients in small amounts, a deficiency can cause big problems. By learning to recognize the signs of a nutrient deficiency and taking prompt action when problems arise, growers can ensure the health and high yield of their cannabis crops. Another way to growers to reduce the maintenance needs of their plants is to purchase easy to grow strains such as Auto Gorilla Glue 4 or Zkittles from a highly reputable seed bank such as I49 to ensure superior genetics.

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