Phosphorus deficiency

Dark, dull or bluish leaves, purple-red stems and slow flower development, often worse when roots are cold or pH is high.

Symptoms

• Dark, dull or bluish-green leaves.
• Purple-red stems and leaf stalks (some plants have purple stems naturally, so look for change).
• Slow flower development.

Quick checks

• Measure root-zone and floor temperature, especially at night.
• Check feed and run-off pH.
• Check EC against the chart.

How to fix it

1. 1
   Environment

   Warm the root zone

   Lift containers off cold floors and keep nights within about 5–8 °C of the daytime temperature.

2. 2
   Check

   Correct pH

   Check the basics first: feed and run-off pH (5.5–6.5), EC for this week, watering, climate and light.

3. 3
   Feed

   Follow the flowering chart

   Bloom A+B at chart strength, plus your chosen PK 9/18 or Resin programme.

Likely causes

• Cold roots (below about 15 °C).
• pH too high, which locks phosphorus up.
• Feed too weak for the stage.

What to avoid

• Don't add more feed if the roots are cold: fix the temperature first.
• Don't assume all purple stems are a problem.

Prevention

• Insulate containers from cold floors in UK winters.
• pH in range.

Monkey products that can help

Bloom A+B

Flowering base feed with phosphorus and potassium raised for flowers.

Follow the flowering chart for the week: equal amounts of Part A and Part B, added separately and never mixed together neat.

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PK 9/18

Phosphorus and potassium supplement for the PK programme. PK 9/18 or Resin, never both.

Follow the PK chart (flower weeks 4–6). Use PK 9/18 OR Resin, never both.

View product →

Products support a healthy plant. They don't replace fixing the cause.

When to get help

If symptoms persist with warm roots and correct pH, email info@monkeynutrients.co.uk with your readings.

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