Zn deficiency in Poinsettia

Zn deficiency in Poinsettia

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Scientific Name
Zinc (Zn)
Atomic Number
30
Atomic Weight u
65.38
Elemental Group
Micro elements (B, Cl, Cu, Fe, Mn, Mo, Ni, Zn) | Micronutrients
Available Forms

Available forms of Zinc (Zn) for use in Pot and Bedding Plants

  • Zinc sulfate (ZnSO₄·7H₂O, “White vitriol”) – soluble, common foliar/substrate application.
  • Zinc sulfate monohydrate (ZnSO₄·H₂O) – slightly more concentrated form of zinc sulfate.
  • Zinc nitrate [Zn(NO₃)₂·6H₂O] – highly soluble, provides Zn and N together.
  • Chelated zinc (Zn-EDTA, Zn-DTPA, Zn-EDDHA) – stable, effective under varying pH, often used in fertigation.
  • Zinc oxide (ZnO) – slow-release, less soluble, often in granular/controlled-release fertilizers.
  • Zinc carbonate (ZnCO₃, “Smithsonite”) – less soluble, slow-release source.
  • Zinc chloride (ZnCl₂) – soluble but less common in horticulture.
  • Zinc frits (glass-fused micronutrients containing Zn) – used in slow-release formulations.

Zinc (Zn) Deficiency in Poinsettia (Pot and Bedding Plants)

Symptoms

  • Young leaves affected first: Zn is not very mobile, so deficiency shows in the youngest foliage.
  • Interveinal chlorosis: Leaves exhibit light green to yellow tissue between veins while veins remain dark green.
  • Rosetting / stunting: Shortened internodes lead to a compact, “rosette” appearance at shoot tips.
  • Leaf distortion: Smaller, narrow, often upward-cupped leaves.
  • Flowering impact: Reduced bract size, delayed flowering, and uneven bract coloration.
  • In severe cases, terminal dieback may occur due to loss of apical dominance.

Causes

  • High media pH (>6.2–6.5) → Zn becomes insoluble and unavailable.
  • Excess phosphorus fertilization → interferes with Zn uptake (“P-induced Zn deficiency”).
  • High bicarbonates in irrigation water → elevate substrate pH and limit Zn solubility.
  • Low organic matter or CEC in potting mixes → Zn not retained, prone to leaching.
  • Continuous use of Zn-free fertilizers without supplementation.

Correction

  • Foliar spray: Apply zinc sulfate (ZnSO₄·7H₂O) at 0.1–0.25% to quickly restore Zn levels.
  • Substrate application: Use Zn-EDTA or Zn-DTPA (chelated Zn) for reliable uptake across pH ranges.
  • Correct pH: Maintain substrate pH between 5.5–6.0 for optimal Zn availability.
  • Micronutrient blends: Incorporate controlled-release or liquid feeds that include Zn.

Prevention

  • Monitor and adjust substrate pH regularly to stay in the optimal range.
  • Avoid excessive use of phosphorus fertilizers, which suppress Zn uptake.
  • Use balanced fertilizers that include Zn as part of the micronutrient package.
  • Conduct regular media and tissue testing to detect early deficiencies.

Zn deficiency in Poinsettia

Scientific Name
Zinc (Zn)
Atomic Number
30
Atomic Weight u
65.38
Elemental Group
Micro elements (B, Cl, Cu, Fe, Mn, Mo, Ni, Zn) | Micronutrients
Available Forms

Available forms of Zinc (Zn) for use in Pot and Bedding Plants

  • Zinc sulfate (ZnSO₄·7H₂O, “White vitriol”) – soluble, common foliar/substrate application.
  • Zinc sulfate monohydrate (ZnSO₄·H₂O) – slightly more concentrated form of zinc sulfate.
  • Zinc nitrate [Zn(NO₃)₂·6H₂O] – highly soluble, provides Zn and N together.
  • Chelated zinc (Zn-EDTA, Zn-DTPA, Zn-EDDHA) – stable, effective under varying pH, often used in fertigation.
  • Zinc oxide (ZnO) – slow-release, less soluble, often in granular/controlled-release fertilizers.
  • Zinc carbonate (ZnCO₃, “Smithsonite”) – less soluble, slow-release source.
  • Zinc chloride (ZnCl₂) – soluble but less common in horticulture.
  • Zinc frits (glass-fused micronutrients containing Zn) – used in slow-release formulations.
Zn deficiency in Poinsettia

Zinc (Zn) Deficiency in Poinsettia (Pot and Bedding Plants)

Symptoms

  • Young leaves affected first: Zn is not very mobile, so deficiency shows in the youngest foliage.
  • Interveinal chlorosis: Leaves exhibit light green to yellow tissue between veins while veins remain dark green.
  • Rosetting / stunting: Shortened internodes lead to a compact, “rosette” appearance at shoot tips.
  • Leaf distortion: Smaller, narrow, often upward-cupped leaves.
  • Flowering impact: Reduced bract size, delayed flowering, and uneven bract coloration.
  • In severe cases, terminal dieback may occur due to loss of apical dominance.

Causes

  • High media pH (>6.2–6.5) → Zn becomes insoluble and unavailable.
  • Excess phosphorus fertilization → interferes with Zn uptake (“P-induced Zn deficiency”).
  • High bicarbonates in irrigation water → elevate substrate pH and limit Zn solubility.
  • Low organic matter or CEC in potting mixes → Zn not retained, prone to leaching.
  • Continuous use of Zn-free fertilizers without supplementation.

Correction

  • Foliar spray: Apply zinc sulfate (ZnSO₄·7H₂O) at 0.1–0.25% to quickly restore Zn levels.
  • Substrate application: Use Zn-EDTA or Zn-DTPA (chelated Zn) for reliable uptake across pH ranges.
  • Correct pH: Maintain substrate pH between 5.5–6.0 for optimal Zn availability.
  • Micronutrient blends: Incorporate controlled-release or liquid feeds that include Zn.

Prevention

  • Monitor and adjust substrate pH regularly to stay in the optimal range.
  • Avoid excessive use of phosphorus fertilizers, which suppress Zn uptake.
  • Use balanced fertilizers that include Zn as part of the micronutrient package.
  • Conduct regular media and tissue testing to detect early deficiencies.