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Cannabis Nitrogen Deficiency: Treating Yellow Leaves

Cannabis Nitrogen Deficiency: Treating Yellow Leaves

Posted by Cara Oorbeck on 6th Dec 2021

Many people enjoy gardening as a hobby. Whether you have a vegetable garden, an abundance of flowers around your home, or enjoy houseplants, gardening can be fun and relaxing. For those of us who live in states where growing cannabis is legal, it can also be a way to produce high quality weed while saving money.

Of course, there is more to growing cannabis than simply putting a few seeds in the ground and hoping for the best. For a variety of reasons, growing marijuana indoors is typically the better option. This means that you will have to learn a lot about what your plants need in order for them to thrive.

One common mistake that many novice growers make is not giving plants enough or the right kind of nutrients. In particular, nitrogen deficiency can result in yellow leaves and stunted growth - leaving you with a subpar crop. Below, we outline how to recognize nitrogen deficiency, and what you can do to treat it. If you’re in the market for high quality plant nutrients, shop Grow Green Wellness’ online store today.

Why Do Cannabis Leaves Turn Yellow?

There are a number of possible causes of yellow leaves in cannabis plants. Growing strong, healthy plants requires finding the right balance of water, humidity, temperature, light, nutrients, and soil pH. If any one of those elements are off, it could lead to problems - such as yellow leaves.

Common causes of yellow leaves include:

  1. Improper pH at the roots, which makes it difficult for the plants to absorb nutrients;
  2. Over or under-watering;
  3. Nitrogen deficiency;
  4. Light burn;
  5. Improper temperature (too hot or too cold);
  6. Iron deficiency;
  7. Magnesium deficiency;
  8. Too little light during the seedling stage;
  9. Bug or pest infestation;
  10. Bud rot.

For many cannabis home growers, nitrogen deficiency is the cause of yellow leaves. Recognizing and properly treating this issue is critical to ensuring that your marijuana plants thrive.

Nitrogen is one of the three primary nutrients - along with potassium and phosphorus - that cannabis plants need to grow. This macronutrient helps plants convert sunlight into energy through the photosynthesis process. It also acts as a building block for the plant proteins and is a component of plant DNA or RNA.

Cannabis plants need high amounts of nitrogen during the vegetative state. Once they reach the flowering state, it is a good idea to taper off the nitrogen to “flush” the plants. This produces a cleaner-tasting bud.

If your cannabis plants do not have enough nitrogen, you will see pale green to pale yellow leaves at the bottom of the plant. This happens because the plant removes chlorophyll - the green pigment responsible for light absorption in plants - from the lower leaves. Because the newer leaves at the top of the plant are closer to the light, they are prioritized and get most of the plant’s nitrogen stores.

Signs of nitrogen deficiency include:

  • Older leaves (lower on the plant) turn yellow, wilt, and drop off;
  • The whole plant appears to be pale or yellowish green in color;
  • Red stems;
  • Drooping leaves;
  • Slow growth rate; and
  • The roots grow at a faster rate than the leaves.

Yellowing older leaves is normal towards the end of the growth cycle, as the plants divert nitrogen towards growing buds. It is a cause for concern when it happens during the vegetative phase. If the yellowing begins to move up the plant, then you will know that you have a nitrogen deficiency - and that it is time to treat your plants.

How Can I Treat Yellow Leaves on My Cannabis Plants?

The easiest way to fix a nitrogen deficiency in your marijuana plants is to add a nitrogen-rich nutrient such a Vegamatrix Grow 5-2-3. This should be done in the vegetative stage, where yellowing leaves are a sign of nitrogen deficiency. Remember that if lower leaves are turning yellow during the flowering stage, it is simply a sign that your plants are using nitrogen to grow bud.

If you aren’t already using a nitrogen-rich nutrient supplement during the vegetative cycle, start by adding nutrients to your regular feeding schedule. Make sure that you add additional fertilizer in small increments. Check the bottle or package of your fertilizer to determine the appropriate amount for your plants.

Adding too much nitrogen can cause nitrogen toxicity. Signs of nitrogen toxicity include shiny, dark green leaves, weak stems, slow overall growth, nd “clawed” leaves. Clawing happens when the tips of the marijuana plant fold downwards, resulting in a claw-like appearance.

During the vegetative phase, nitrogen toxicity is rare because the plants are using so much nitrogen to grow. However, if you add a large amount of a nitrogen-rich supplement, it may cause problems for your cannabis plants. During the flowering stage, nitrogen toxicity is more common, so be careful to not overdo the nitrogen.

When feeding your plants, be sure to check the pH balance of the run-off to make sure that the pH levels are appropriate. If the pH is too high or too low, it can affect your plants’ ability to uptake the nitrogen. For plants grown in soil, the pH level should be between 6.0 and 7.0. For plants grown in hydroponics or soilless mediums, the ideal pH is between 5.5 and 6.5. Supplements like TNB Naturals pH Down or pH Up can help you get to the optimal pH level.

In addition to a nitrogen-rich fertilizer, consider adding a calcium-magnesium (cal mag) supplement. Both of these micronutrients are necessary for plant growth. Adding a supplement like Dakine CalMag to your plants’ regular feeding schedule can increase uptake of vital nutrients - like nitrogen.

After a week of adding nitrogen to their feedings, your cannabis plants should recover. The yellow leaves will have to be removed, but your plants should otherwise be healthy and strong. Be sure to keep feeding a nitrogen-rich fertilizer during the vegetative phase to avoid any future nitrogen deficiencies.

Grow Strong, Healthy Plants with Grow Green Wellness

Growing marijuana at home can be a rewarding experience - and a way to produce high quality bud that meets your specific needs. If you have made the decision to grow cannabis, you want to make sure that your investment is a sound one. Grow Green Wellness’ line of grow accessories can help you achieve your goals.

We carry a range of grow tents, propagation and cloning items, plant nutrients, click and grow pods, and other accessories to help make your project a success. We want you to be able to grow like a pro - and offer you both the tools and the information that you need to make it happen. To learn more or for help choosing a product, give us a call at 616-536-2041 or fill out our online contact form.