Fe deficiency in Pelargonium

Fe deficiency in Pelargonium

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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 use in Pot and Bedding Plants

  • Ferrous sulfate (FeSO₄·7H₂O, “Iron sulfate”) – soluble, fast-acting; foliar or drench.
  • Ferric sulfate (Fe₂(SO₄)₃, “Iron(III) sulfate”) – soluble, acidifying; media drenches in some programs.
  • Iron chelate (Fe-EDDHA, “EDDHA-Fe”) – highly stable, effective in high-pH media.
  • Iron chelate (Fe-DTPA, “DTPA-Fe”) – effective to about pH 7; common in fertigation.
  • Iron chelate (Fe-EDTA, “EDTA-Fe”) – economical; use only in acidic substrates (pH ≤6).
  • Iron citrate (C₆H₅FeO₇, “Ferric citrate”) – soluble organic form for foliar/specialty use.
  • Iron lignosulfonate (varied composition, “Iron lignosulfonate”) – organic complex; soil/media application.
  • Iron frits (varied composition, “Slow-release Fe frits”) – glass-fused carriers for controlled release.

Iron (Fe) Deficiency in Pelargonium (Pot and Bedding Plants)

Symptoms

  • Interveinal chlorosis on the youngest leaves – leaf lamina turns yellow while veins remain green, producing a netted pattern.
  • In severe deficiency, new leaves may become almost white, brittle, and fail to expand normally.
  • Growth tips weaken, with shortened internodes and reduced shoot extension.
  • Reduced flower initiation and smaller blooms with poor color.
  • Prolonged deficiency can lead to necrosis at leaf margins and dieback of shoot tips.

Causes

  • High substrate pH (>6.0–6.5) reducing Fe solubility and uptake.
  • Irrigation water with high bicarbonate levels leading to gradual alkalinity in container mixes.
  • Over-liming or use of alkaline components in potting substrates (e.g., excess dolomite).
  • Excess phosphorus (P) fertilization, which ties up Fe in the substrate.
  • High levels of manganese (Mn), zinc (Zn), or copper (Cu) that antagonize Fe uptake.
  • Poor root function due to compaction, waterlogging, or root pathogens, limiting Fe absorption.
  • Pelargonium species are particularly sensitive to pH drift in container-grown systems.

Correction

  • Foliar sprays:
  • Iron chelates (Fe-EDDHA, Fe-DTPA, Fe-EDTA depending on pH) for rapid correction.
  • Iron sulfate (FeSO₄·7H₂O) at low concentrations, though risk of leaf burn if over-applied.
  • Soil/media drenches:
  • Fe-EDDHA most effective at high pH (stable up to pH 9).
  • Fe-DTPA works in slightly acidic to neutral mixes (up to pH 7).
  • pH adjustment:
  • Adjust container substrate pH to 5.5–6.0.
  • Use ammonium-based fertilizers (e.g., ammonium sulfate, urea) instead of nitrate-based forms to promote localized acidification in the root zone.
  • Irrigation water treatment:
  • Acidify irrigation water if alkalinity (bicarbonates) is high using sulfuric or phosphoric acid injection.

Prevention

  • Maintain container mix pH at 5.5–6.0, ideal for Pelargonium.
  • Monitor irrigation water alkalinity regularly; correct high bicarbonates to prevent pH drift.
  • Include Fe-chelates (especially Fe-EDDHA in alkaline conditions) in ongoing fertigation programs.
  • Avoid overuse of lime and high-P fertilizers in potting mixes.
  • Maintain healthy root systems through well-drained substrates and root disease management.
  • Regularly conduct leaf tissue and substrate tests to detect early nutrient imbalances.

Fe deficiency in Pelargonium

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 use in Pot and Bedding Plants

  • Ferrous sulfate (FeSO₄·7H₂O, “Iron sulfate”) – soluble, fast-acting; foliar or drench.
  • Ferric sulfate (Fe₂(SO₄)₃, “Iron(III) sulfate”) – soluble, acidifying; media drenches in some programs.
  • Iron chelate (Fe-EDDHA, “EDDHA-Fe”) – highly stable, effective in high-pH media.
  • Iron chelate (Fe-DTPA, “DTPA-Fe”) – effective to about pH 7; common in fertigation.
  • Iron chelate (Fe-EDTA, “EDTA-Fe”) – economical; use only in acidic substrates (pH ≤6).
  • Iron citrate (C₆H₅FeO₇, “Ferric citrate”) – soluble organic form for foliar/specialty use.
  • Iron lignosulfonate (varied composition, “Iron lignosulfonate”) – organic complex; soil/media application.
  • Iron frits (varied composition, “Slow-release Fe frits”) – glass-fused carriers for controlled release.
Fe deficiency in Pelargonium
Image Source: Everris Research (NL), care of ICL

Iron (Fe) Deficiency in Pelargonium (Pot and Bedding Plants)

Symptoms

  • Interveinal chlorosis on the youngest leaves – leaf lamina turns yellow while veins remain green, producing a netted pattern.
  • In severe deficiency, new leaves may become almost white, brittle, and fail to expand normally.
  • Growth tips weaken, with shortened internodes and reduced shoot extension.
  • Reduced flower initiation and smaller blooms with poor color.
  • Prolonged deficiency can lead to necrosis at leaf margins and dieback of shoot tips.

Causes

  • High substrate pH (>6.0–6.5) reducing Fe solubility and uptake.
  • Irrigation water with high bicarbonate levels leading to gradual alkalinity in container mixes.
  • Over-liming or use of alkaline components in potting substrates (e.g., excess dolomite).
  • Excess phosphorus (P) fertilization, which ties up Fe in the substrate.
  • High levels of manganese (Mn), zinc (Zn), or copper (Cu) that antagonize Fe uptake.
  • Poor root function due to compaction, waterlogging, or root pathogens, limiting Fe absorption.
  • Pelargonium species are particularly sensitive to pH drift in container-grown systems.

Correction

  • Foliar sprays:
  • Iron chelates (Fe-EDDHA, Fe-DTPA, Fe-EDTA depending on pH) for rapid correction.
  • Iron sulfate (FeSO₄·7H₂O) at low concentrations, though risk of leaf burn if over-applied.
  • Soil/media drenches:
  • Fe-EDDHA most effective at high pH (stable up to pH 9).
  • Fe-DTPA works in slightly acidic to neutral mixes (up to pH 7).
  • pH adjustment:
  • Adjust container substrate pH to 5.5–6.0.
  • Use ammonium-based fertilizers (e.g., ammonium sulfate, urea) instead of nitrate-based forms to promote localized acidification in the root zone.
  • Irrigation water treatment:
  • Acidify irrigation water if alkalinity (bicarbonates) is high using sulfuric or phosphoric acid injection.

Prevention

  • Maintain container mix pH at 5.5–6.0, ideal for Pelargonium.
  • Monitor irrigation water alkalinity regularly; correct high bicarbonates to prevent pH drift.
  • Include Fe-chelates (especially Fe-EDDHA in alkaline conditions) in ongoing fertigation programs.
  • Avoid overuse of lime and high-P fertilizers in potting mixes.
  • Maintain healthy root systems through well-drained substrates and root disease management.
  • Regularly conduct leaf tissue and substrate tests to detect early nutrient imbalances.