When your plants are deficient in phosphorus, this can overall reduce the size of your plants. Not enough causes slow growth and causes the plant to become weak, to little amount of Phosphorus causes slow growths in leaves that may or may not drop off. The edges all around the leaves or half of the leaves can be brownish and work its way inwards a bit causing the part of the leaves to curl up in the air a bit. Fan leaves will show dark greenish/purplish and yellowish tones along with a dullish blue color to them. Sometimes the stems can be red, along with red petioles that can happen when having a Phosphorus deficiency. This isn’t a sure sure sign of you having one though, but can be a sign. Some strains just show the red petioles and stems from its genes.
So pretty much the overall dark green color with a purple, red, or blue tint to the fan leaves is a good sign of a Phosphorus deficiency. Having Cold weather (below 50F/10C) can make phosphorous absorption very troublesome for plants.
Many people get a Phosphorus deficiency confused with a fungus problem because the ends of the leaves look like a fungus problem, But the damage occurs at the end of the leaves. side of the leaves and has a glass like feeling to it as if it had a ph problem. Parts affected by a phosphorus deficiency are: Older Leaves, Whole plant, Petioles.
Too much Phosphorus levels affect plant growth by suppressing the uptake of: Iron, potassium and Zinc, potentially causing deficiency symptoms of these nutrients to occur def in plants. A Zinc deficiency is most common under excessive phosphorus conditions,
As well as causing other nutrients to have absorption troubles like zinc and copper. Phosphorus fluctuates when concentrated and combined with calcium