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Low
Nutrient Deficiency

Purple stems and undersides of leaves

Stems and the undersides of older leaves develop a purple or reddish tint.

Commonly affects: Tomatoes, Peppers, Strawberries, All flowering crops

What you'll see

  • Purple or red coloration on stems
  • Undersides of older leaves turn purple
  • Slow growth, especially of roots and flowers
  • Often worse in cold weather

Likely causes

  • Phosphorus deficiency or lock-out
  • Cold root zone (<16 °C) reduces phosphorus uptake — most common cause
  • Low pH (<5.3) or very high pH (>7.0)
  • Incorrect mixing of the complete MICRO, GROW and BLOOM system

How to fix it (step by step)

  1. 1Warm the reservoir and root zone to 18–22 °C
  2. 2Confirm pH is 5.5–6.0
  3. 3Check the complete 3+3+3 mL/L dose, mixing order and tank pH rather than adding extra BLOOM
  4. 4Do a fresh reservoir mix at full strength

Stop it happening again

  • Insulate outdoor reservoirs, use a small aquarium heater in winter
  • Keep using all three parts together at the approved dose; do not switch to a BLOOM-heavy ratio

Recommended products

Part 3 · Use with MICRO and GROW

NaO BLOOM

Phosphorus, potassium and magnesium · Part 3 of 3

View product

Need a second opinion?

Share dated photos, root observations, water readings and your mixing record so our team can assess the problem. Visual symptoms alone do not confirm a diagnosis.

Confirm the cause before treating the crop

Collect observations that distinguish possible causes

Record the first appearance of symptoms, the affected plants and whether old or new tissue is involved. Inspect roots, delivery and visible pests. Compare a healthy plant nearby. Record pH, EC, temperature and recent changes. Several causes may act together; the symptom title is a starting point, not a confirmed diagnosis.

Verify calibration and the complete mixing record. Product links explain nutrient roles; they are not instructions to use one bottle alone. Record your correction and assess subsequent growth because damaged leaves and fruit may not recover.

Escalate safely

Rapid wilting, collapse or spreading root symptoms need prompt checks of flow, oxygen and hygiene. Protect unaffected plants where practical and seek qualified diagnosis. Treatments must be registered for their intended crop and use and applied according to label, including harvest intervals.

When asking for help, provide dated root and leaf photos, water readings and mixing records. Do not combine nutrient changes with disinfectants or pesticides without compatibility advice. An online guide cannot confirm a pathogen or prescribe a universal chemical treatment.

Further reading

These sources support general cultivation guidance, not verified Nana Organics product performance. Current NaO instructions take precedence over another brand’s feeding schedule.