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How to Identify Macro-Nutrient Deficiencies in Cannabis Plants

A deficiency in a macro-nutrient (an element plants need in large amounts) can manifest in a marijuana plant under poor growing conditions or stress (overwatering, overheating, transplanting, etc.) and it's important that cannabis growers know how to identify different ones. To give you an idea of what to look for, here we talk about how to identify some of the most common macro-nutrient deficiencies in cannabis plants.

  • Calcium (CA)
    A lack of Calcium in cannabis plants pervents flowers from fully developing, weakens their ability to take the heat, and eventually causes the soil to turn too acidic to support healthy root growth. Calcium deficiencies show up in the newest vegetation as stunted or deformed growth, leaf curling or die-off, flimsy or hollow stems, and distorted or discolored leaves.
  • Nitrogen (N)
    You can identify a Nitrogen deficiency in cannabis plants by the red stems that develop and the quick yellowing of the older, lower leaves that spreads upwards. Other symptoms includ stunted growth, a pale overall appearance, and leaves that wilt, curl, turn brown, and eventually die.
  • Phosphorous (P)
    You can tell that a marijuana plant had a Phosphorous deficiency by the dark shade of shiny green lower eaves turn and the blue, purple, or bronze spots that appear on them. You'll also see slowed or deformed growth, bright red or purple colored stems, and leaves that curl, thicken and feel stiff before turning brown or yellow and falling off.
  • Potassium (K)
    A cannabis plant with a Potassium deficiency shows symptoms like stretched, spindly growth as well as top and bottom leaves that turn brown. The leaves also exhibit burnt, curling edges with yellowing margins.
  • Sulfer (S)
    You can identify a lack of Sulfer in your cannabis plant apart from other nutrient deficiences that cause chlorosis (yellowing of leaves) by the fact that it begins at the leaf base rather than the tips. It affects the plant all over (starting with the newest growth), and the underside of leaves may turn pink, red, or orange.
  • Magnesium (MG)
    Signs of a magnesium deficiency start in the middle of cannabis plants and spread to the new growth; the leaves turn light green, yellow, or even white while the edges and viens remain dark green.


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