top of page

Phosphorus Deficiency

Phosphorus Deficiency

Have Photos?

Photos Coming Soon

A cannabis phosphorus deficiency primarily affects the lower and older leaves of the plant. These leaves may exhibit dark green or yellow discoloration, accompanied by brown, bronze, or blue spots and splotches. The affected leaves can become thickened and curled, appearing stiff. In some cases, the stems of the plant may turn bright red or purple, though not always. It's worth noting that a phosphorus deficiency can sometimes be accompanied by a calcium deficiency since these two nutrients interact within the plant. This deficiency is more commonly observed after the plant starts forming buds, as phosphorus demands increase during this stage.

Cause of Issue
◉ Improper pH levels at the plant's roots, hindering phosphorus absorption ◉ Overwatering or compacted soil, which can contribute to nutrient uptake issues
Symptoms
◉ Darkening of leaves, appearing dark green, blue, or grayish ◉ Yellowing of leaves, particularly if left untreated or combined with other nutrient deficiencies or pH problems ◉ Bronze, purple, or brown spots and splotches on leaves ◉ Thickened leaves that may feel dry or stiff ◉ Bright red or purple stems, although not always present ◉ Potential co-occurrence of a calcium deficiency due to the interaction between phosphorus and calcium within the plant
Corrective Actions
◉ Adjust pH: Ensure that the pH of the root zone falls within the correct range. For soil cultivation, maintain a pH of 6.2-7.0, while for hydroponics, aim for a pH of 5.5-6.2. ◉ Care for the roots: Avoid overwatering and ensure proper drainage to prevent compacted soil, as it can trigger a phosphorus deficiency. ◉ Provide suitable temperature: Maintain a comfortable room temperature for your cannabis plants, avoiding extremes that can impede phosphorus absorption. ◉ Use the right nutrients: Most cannabis-friendly nutrient formulations already contain sufficient phosphorus. However, excess iron (Fe) and zinc (Zn) can hinder phosphorus absorption. If you suspect nutrient salt buildup, flush the plant with properly pH-adjusted water containing nutrients, including phosphorus. Choose nutrient sources rich in phosphorus, such as bat guano, bone or blood meal, worm castings or tea, soft rock phosphate, fish meal, crabshell, or specialized "bloom" or "flowering" nutrients formulated for cannabis. ◉ Monitor root health: Maintain healthy roots by following proper watering practices and avoiding overwatering. ◉ Observe recovery: After implementing the necessary steps, monitor your plants for signs of improvement. New leaves should no longer exhibit symptoms within approximately a week, indicating successful recovery. However, keep in mind that leaves damaged by a phosphorus deficiency may not regain their normal color. ◉ Remember to consider these recommendations while also adapting them to your specific growing environment and circumstances.
Canniversity is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.
bottom of page