Iron (Fe) Deficiency

Iron (Fe) Deficiency

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Scientific Name
Iron (Fe)
Atomic Number
26
Atomic Weight u
55.845
Elemental Group
Micro elements (B, Cl, Cu, Fe, Mn, Mo, Ni, Zn) | Micronutrients
Available Forms

Available forms of Iron (Fe) for Horticultural Production

  • Ferrous sulfate (FeSO₄·7H₂O, “Iron sulfate”) – soluble, fast-acting; commonly used in foliar sprays and soil drenches for quick correction.
  • Ferric sulfate (Fe₂(SO₄)₃, “Iron(III) sulfate”) – soluble, strongly acidifying; occasionally used in substrate drenches.
  • Iron chelate (Fe-EDDHA, “EDDHA-Fe”) – highly stable, effective up to pH 9; best choice for alkaline or high-pH substrates.
  • Iron chelate (Fe-DTPA, “DTPA-Fe”) – stable to about pH 7; widely used in fertigation for container and bedding plants.
  • Iron chelate (Fe-EDTA, “EDTA-Fe”) – economical, but effective only in acidic media (pH ≤6).
  • Iron citrate (C₆H₅FeO₇, “Ferric citrate”) – soluble organic form; sometimes used in foliar applications and specialty solutions.
  • Iron lignosulfonate (varied composition, “Iron lignosulfonate”) – natural organic chelate; moderate stability, used in soil or container applications.
  • Iron frits (varied composition, “Slow-release Fe frits”) – glass-fused carriers providing controlled Fe release in substrates and potting mixes.

Iron (Fe) Deficiency

Container Nursery Stock, Pot & Bedding Plants

Symptoms

  • Young foliage shows interveinal chlorosis – leaves turn pale yellow to almost white while veins remain green.
  • In severe cases, new growth may appear bleached or whitish, with brittle or poorly expanded leaves.
  • Growth tips weaken, internodes shorten, and shoots become spindly or stunted.
  • Necrosis may develop at leaf margins, tips, or needle ends in prolonged deficiency.
  • Overall decline in plant vigor, reduced shoot extension, smaller leaves, poor flowering or bud set, and diminished ornamental value.

Causes

  • High substrate pH (>6.0–6.5) reducing Fe solubility and uptake – the most common cause.
  • Alkaline irrigation water with high bicarbonate or carbonate levels raising pH over time.
  • Excess liming or alkaline components (dolomite, CaCO₃) in container mixes.
  • Excess phosphorus fertilization tying up Fe in the root zone.
  • High manganese (Mn), zinc (Zn), or copper (Cu) competing with Fe absorption.
  • Poor root health from compaction, waterlogging, or pathogens reducing uptake capacity.
  • Sensitive crops (e.g., Hydrangea, Rosa, Pelargonium, Chamaecyparis) are especially prone in alkaline conditions.

Correction

  • Foliar sprays: Apply soluble Fe sources for rapid greening response:
    • Iron chelates (Fe-EDDHA, Fe-DTPA, Fe-EDTA depending on media pH).
    • Iron sulfate (FeSO₄·7H₂O) at low concentrations (caution: possible leaf burn).
  • Soil/media drenches:
    • Fe-EDDHA – most effective under high pH, stable up to pH 9.
    • Fe-DTPA – suitable for neutral to slightly acidic media (up to pH 7).
    • Fe-EDTA – effective only at low pH.
  • pH management:
    • Lower substrate pH to 5.0–5.5 (Hydrangea, Potentilla) or 5.5–6.0 (Pelargonium, Rosa, Calibrachoa).
    • Use acidifying fertilizers (e.g., ammonium sulfate, urea) instead of nitrate-based sources.
  • Irrigation adjustment: Acidify high-alkalinity water with sulfuric, phosphoric, or citric acid to neutralize bicarbonates.

Prevention

  • Maintain container media pH in the optimal range (generally 5.0–6.0) depending on species.
  • Test irrigation water alkalinity regularly and acidify if bicarbonates are high.
  • Include Fe-chelates (especially Fe-EDDHA under alkaline conditions) preventively in fertigation programs.
  • Avoid over-liming and excessive phosphorus fertilization.
  • Ensure healthy root systems with well-drained substrates, good aeration, and disease management.
  • Conduct routine substrate testing and leaf tissue analysis to detect early nutrient imbalances.

Iron (Fe) Deficiency

Iron (Fe)
Scientific Name
Iron (Fe)
Atomic Number
26
Atomic Weight u
55.845
Elemental Group
Micro elements (B, Cl, Cu, Fe, Mn, Mo, Ni, Zn) | Micronutrients
Available Forms

Available forms of Iron (Fe) for Horticultural Production

  • Ferrous sulfate (FeSO₄·7H₂O, “Iron sulfate”) – soluble, fast-acting; commonly used in foliar sprays and soil drenches for quick correction.
  • Ferric sulfate (Fe₂(SO₄)₃, “Iron(III) sulfate”) – soluble, strongly acidifying; occasionally used in substrate drenches.
  • Iron chelate (Fe-EDDHA, “EDDHA-Fe”) – highly stable, effective up to pH 9; best choice for alkaline or high-pH substrates.
  • Iron chelate (Fe-DTPA, “DTPA-Fe”) – stable to about pH 7; widely used in fertigation for container and bedding plants.
  • Iron chelate (Fe-EDTA, “EDTA-Fe”) – economical, but effective only in acidic media (pH ≤6).
  • Iron citrate (C₆H₅FeO₇, “Ferric citrate”) – soluble organic form; sometimes used in foliar applications and specialty solutions.
  • Iron lignosulfonate (varied composition, “Iron lignosulfonate”) – natural organic chelate; moderate stability, used in soil or container applications.
  • Iron frits (varied composition, “Slow-release Fe frits”) – glass-fused carriers providing controlled Fe release in substrates and potting mixes.
Iron (Fe) Deficiency
Image Source: Everris Research (NL), LVG Bad Zwischenahn (D), LVG Heidelberg (D), care of ICL

Iron (Fe) Deficiency

Container Nursery Stock, Pot & Bedding Plants

Symptoms

  • Young foliage shows interveinal chlorosis – leaves turn pale yellow to almost white while veins remain green.
  • In severe cases, new growth may appear bleached or whitish, with brittle or poorly expanded leaves.
  • Growth tips weaken, internodes shorten, and shoots become spindly or stunted.
  • Necrosis may develop at leaf margins, tips, or needle ends in prolonged deficiency.
  • Overall decline in plant vigor, reduced shoot extension, smaller leaves, poor flowering or bud set, and diminished ornamental value.

Causes

  • High substrate pH (>6.0–6.5) reducing Fe solubility and uptake – the most common cause.
  • Alkaline irrigation water with high bicarbonate or carbonate levels raising pH over time.
  • Excess liming or alkaline components (dolomite, CaCO₃) in container mixes.
  • Excess phosphorus fertilization tying up Fe in the root zone.
  • High manganese (Mn), zinc (Zn), or copper (Cu) competing with Fe absorption.
  • Poor root health from compaction, waterlogging, or pathogens reducing uptake capacity.
  • Sensitive crops (e.g., Hydrangea, Rosa, Pelargonium, Chamaecyparis) are especially prone in alkaline conditions.

Correction

  • Foliar sprays: Apply soluble Fe sources for rapid greening response:
    • Iron chelates (Fe-EDDHA, Fe-DTPA, Fe-EDTA depending on media pH).
    • Iron sulfate (FeSO₄·7H₂O) at low concentrations (caution: possible leaf burn).
  • Soil/media drenches:
    • Fe-EDDHA – most effective under high pH, stable up to pH 9.
    • Fe-DTPA – suitable for neutral to slightly acidic media (up to pH 7).
    • Fe-EDTA – effective only at low pH.
  • pH management:
    • Lower substrate pH to 5.0–5.5 (Hydrangea, Potentilla) or 5.5–6.0 (Pelargonium, Rosa, Calibrachoa).
    • Use acidifying fertilizers (e.g., ammonium sulfate, urea) instead of nitrate-based sources.
  • Irrigation adjustment: Acidify high-alkalinity water with sulfuric, phosphoric, or citric acid to neutralize bicarbonates.

Prevention

  • Maintain container media pH in the optimal range (generally 5.0–6.0) depending on species.
  • Test irrigation water alkalinity regularly and acidify if bicarbonates are high.
  • Include Fe-chelates (especially Fe-EDDHA under alkaline conditions) preventively in fertigation programs.
  • Avoid over-liming and excessive phosphorus fertilization.
  • Ensure healthy root systems with well-drained substrates, good aeration, and disease management.
  • Conduct routine substrate testing and leaf tissue analysis to detect early nutrient imbalances.