Nitrogen is the predominant compound found in cannabis nutrients, especially during the vegetative phase. Nitrogen toxicity will be quickly followed by more severe symptoms.
One of the numerous benefits of growing in organic soil is that it provides a buffer zone of organisms around the root system. Soil grown plants are more resilient to overfeeding and other stressors. A well-prepared organic soil really needs no nutrients for the entire grow cycle, removing the danger of burning altogether.
Nutrient burn can affect cannabis during any stage of growth. Prevention, identification, and remediation are all essential pieces of knowledge in the cannabis grower’s arsenal.
Prevention is always the best policy, so it is a bright idea to develop good habits that decrease the chances of mistakes. First of all, be sure to use the correct nutrients for the appropriate growth stage. Even then, it is a wise idea to only use ¾ the recommended dosage on product packaging. Sometimes, manufacturer recommendations can run things a bit “hot,” which leaves little room for error.
- Mixing nutrients stronger than recommended during any phase of growth
- Overwatering; plants need a dry period to function properly and access oxygen
- Using bloom boosters too often or in too high a concentration
- Using growth stimulants too regularly, causing dwarfism and burning due to excessive nutrient uptake
Nutrient burn can be caused by:
Use an EC/pH meter to check nutrient strength every time, whether hand mixing daily or in hydro reservoirs. Be sure to flush hydroponic systems, grow mediums, and soils to prevent salt build-up in the root zone.
Nutrient burn can be gradual if the overdose is only slightly stronger. It can also be rapid-appearing, progressing over a few days. The worst-case scenario is a chronic overdose that causes crop-wide yellowing and wilting overnight with leaf curl and lack of turgidity. In this case, if during the vegetative phase, start again. Recovery may be impossible or take longer than restarting completely.
If you are mixing daily by hand, then calm down tiger, less is more with cannabis. Keep in mind that satisfactory results can be obtained with just plain water for the whole life of the plant.
Over-enthusiasm with nutrients can burn marijuana plants. Knowledge is power when it comes to big buds. So, how to prevent and treat nutrient burn?
But cannabis plants need relatively low levels of Nitrogen in the second half of the flowering/budding stage. While your plants still need N (nitrogen) during flowering, too much N at this stage will prevent your plants from forming buds properly, resulting in lower yields, less potency and possibly inferior buds.
Many new growers accidentally give their plants give too much Nitrogen, especially in the flowering stage. This results in dark, shiny, clawing leaves.
Pretty much any complete plant food
- Marijuana plants that get too much Nitrogen in the vegetative stage don’t grow as vigorously.
- Too much nitrogen is especially harmful in the flowering stage, because this will cause your plant to produce much smaller buds.
- If you react quickly and reduce your nitrogen levels at the first sign of toxicity, your plant will quickly recover.
Note: During the last few weeks before harvest, marijuana plants starts pulling all the remaining nitrogen from her leaves as part of the bud-making process. This causes yellowing leaves starting towards the bottom of the plant. This is part of the natural flowering process and you don’t need to fight it. You may notice that marijuana leaves are yellowing in almost all pictures of marijuana plants with big buds that are close to harvest. You tend to get smaller yields at harvest from nitrogen-toxic plants with dark green leaves.
Leaves that turn into claws often start turning yellow and dying if the nitrogen toxicity is not treated, much like a nitrogen deficiency, only the leaves will continue to get more and more clawed. Leaves eventually turn yellow or brown and fall off. You can tell if yellowing is caused by too much nitrogen because the rest of the plant will be dark green, and the yellowing leaves will turn into claws first.
Vegetative Stage – higher levels of Nitrogen (pretty much any plant food will do)
Flowering Stage – lower levels of Nitrogen (use “Bloom” or Cactus nutrients)
Effected leaves likely won’t recover, but you should see the problem halt with no new leaves being affected.
Does your plant have "the claw?" The talon-like leaves that are bent at the ends are a sign that your plant may have nitrogen toxicity. Learn how to fix it.