Different cannabis strains have different ideal nutrient ratios, but they all require vital nutrients to grow healthy and strong. Unfortunately, many growers do not provide their plants with the right mix of nutrients, leading to deficiencies that can stunt growth, lower yields, and cause other problems.
Identifying nutrient deficiencies can be tricky, as the symptoms can be similar to those caused by other problems, such as pests or diseases. However, there are some general signs to look for that can indicate a nutrient deficiency.
Nitrogen deficiency
This is one of the most common cannabis nutrient deficiencies. Cannabis plants need nitrogen for growth and development, so lacking this nutrient can lead to stunted growth, yellowing leaves, and slow development. Other symptoms of nitrogen deficiency include small leaves, fewer leaves, and a general lack of vigor.
However, don’t be confused with nitrogen toxicity, which can also cause leaves to turn yellow. The difference is that with nitrogen toxicity, the new growth at the tips of the leaves will be yellow, while with nitrogen deficiency, the older leaves will turn yellow first and then progress up the plant.
Run some tests on your water and soil to see if nitrogen is low, and then fertilize accordingly. Be careful not to overdo it, as too much nitrogen can harm your plants. Also, ensure you use a fertilizer high in nitrogen, as other nutrients will not do much to alleviate the deficiency.
Phosphorus Deficiency
Phosphorus is another essential nutrient for cannabis plants, and it is often one of the first nutrients to become depleted in soil. Phosphorus is responsible for energy transfer and storage in plants so that a deficiency can lead to stunted growth, slow development, and reduced yields. Plants with a phosphorus deficiency may also have purplish or reddish and small, dark-green leaves.
As with nitrogen, too much phosphorus can be as harmful as too little. If you suspect your plant has a phosphorus deficiency, test the soil and water to see if they are low in this nutrient. You can also try preventing the deficiency by using a fertilizer high in phosphorus, but be sure not to overdo it. A natural way to add phosphorus to the soil is using bone meal. To do this, mix bone meal into the soil around your plants.
Potassium Deficiency
Potassium is one of the most important nutrients for cannabis plants, and a deficiency can cause several problems. This nutrient helps with photosynthesis, water uptake, and the movement of nutrients throughout the plant. A potassium deficiency can cause leaves to be yellow or brown and curl at the edges. It can also lead to stunted growth and smaller yields.
To correct a potassium deficiency, growers can use a potassium-based fertilizer or add potassium sulfate to their soil. However, before fixing a deficiency, it is always best to test the soil to ensure potassium is the problem.
But why is testing essential? First, over-fertilizing with potassium can cause problems, such as root burn, so it is essential to ensure that the problem is indeed a deficiency.
Calcium Deficiency
Calcium is essential for developing strong cell walls, and a deficiency can lead to stunted growth and problems with the roots. Symptoms of a calcium deficiency include yellowing leaves (usually starting at the bottom of the plant), small or stunted leaves, and leaf tips that curl downwards. Unfortunately, these symptoms can also be caused by other problems, so it is important to look for other signs of a calcium deficiency, such as soft or spongy stems.
Providing your plants with the right calcium is crucial to prevent deficiencies. The best way to do this is to use a calcium-rich fertilizer, such as bone meal or limestone. Like any other deficiency, it is important to catch a calcium deficiency early, as it can be difficult to correct once the plant is already stunted.
Magnesium Deficiency
Magnesium plays an important role in photosynthesis, and a deficiency can lead to yellowing leaves (starting at the bottom of the plant). Unlike with a calcium deficiency, the leaves will not curl downwards. Magnesium deficiency is also often accompanied by a potassium deficiency, as these two nutrients work together in the plant.
A magnesium deficiency can be corrected using a magnesium-rich fertilizer, such as Epsom salt. It is important to ensure that your plants get enough water, as magnesium is water soluble and can be easily washed away.
Sulfur Deficiency
Sulfur may seem unlikely to be deficient, but it’s pretty common, especially in hydroponic systems. In addition, sulfur is necessary to produce chlorophyll, so a deficiency will lead to yellowing leaves (between the veins) and slow growth.
Add a sulfur-based fertilizer to your nutrient solution to correct a sulfur deficiency. However, be careful not to overdo it, as too much sulfur can harm plant growth.
Iron Deficiency
Iron is another nutrient that is essential for chlorophyll production. An iron deficiency will lead to yellowing leaves (between the veins), stunted growth, and weak stems. Yellowing leaves have other causes, so check for other nutrient deficiencies before assuming it’s iron.
You can use an iron-based fertilizer or chelate to correct an iron deficiency. Iron can also be applied as a foliar spray, but avoid getting any on the leaves as this can cause burning.
Bottom Line
Testing your soil is the best way to determine your plants’ nutrients. Nutrient deficiencies can cause various problems, from yellowing leaves to stunted growth. If you think your plants may be deficient in a certain nutrient, the best way to correct the problem is to use fertilizer or add the nutrient to your soil. However, be careful not to overdo it, as too much of any nutrient can harm plants.
