S deficiency in Pelargonium

S deficiency in Pelargonium

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Scientific Name
Sulfur (S)
Atomic Number
16
Atomic Weight u
32.06
Elemental Group
Meso elements (Ca, Mg, S ) | Secondary macronutrients
Available Forms

Available forms of Sulfur (S) for use in Pot and Bedding Plants

  • Elemental sulfur (S⁰) – slow-release, used in granular or powder form; requires microbial oxidation to become plant-available.
  • Gypsum (CaSO₄·2H₂O) – provides both Ca and S; moderately soluble, mainly used in substrate amendment.
  • Magnesium sulfate (MgSO₄·7H₂O, “Epsom salt”) – soluble, provides Mg and S; rapid correction via foliar or substrate application.
  • Potassium sulfate (K₂SO₄, “Sulfate of potash”) – soluble, supplies both K and S; commonly used in fertigation.
  • Ammonium sulfate ((NH₄)₂SO₄) – soluble, provides both N and S; good for quick substrate correction.
  • Sodium sulfate (Na₂SO₄, “Glauber’s salt”) – soluble, less commonly used in horticulture; can correct S deficiency.
  • Chelated sulfur compounds – specialized foliar products providing rapid S uptake in acidic or high-pH media.

Sulfur (S) Deficiency in Pelargonium (Geraniums) - Pot and Bedding Plants

Symptoms

  • General chlorosis (yellowing) of younger leaves first (unlike N deficiency which starts in older leaves).
  • Leaves may appear pale green to yellow, sometimes with a reddish or purplish tinge on veins or petioles.
  • Stunted growth and reduced branching, plants look spindly.
  • Flower initiation and development delayed → fewer and smaller blooms.
  • Severe deficiency can lead to thin, brittle stems and poor canopy coverage.

Causes

  • Low sulfur availability in substrate: common when soilless media with little organic matter are used.
  • Use of high-purity fertilizers (e.g., calcium nitrate, potassium nitrate) with little or no sulfate.
  • Leaching in containers due to frequent irrigation.
  • Low atmospheric sulfur deposition (decline in industrial SO₂ emissions has reduced background sulfur inputs).

Correction

  • Apply sulfate-based fertilizers, e.g.:
  • Magnesium sulfate (Epsom salts)
  • Potassium sulfate
  • Ammonium sulfate (if extra N is also required)
  • Foliar sprays with magnesium sulfate (1–2 g/L) can provide rapid but temporary relief.
  • Adjust fertigation to include balanced S sources (e.g., 20-20-20 with sulfate form).

Prevention

  • Regularly incorporate S-containing fertilizers in the nutrient program (avoid exclusive reliance on nitrate salts).
  • Use complete water-soluble fertilizers with at least 50–75 ppm S.
  • Monitor substrate solution (EC & ion analysis) to confirm adequate sulfur (target: ~50–80 ppm S).
  • Avoid excessive leaching that strips sulfates from container media.
  • Maintain balanced Ca:Mg:S ratio to prevent antagonisms.

S deficiency in Pelargonium

Sulfur (S)
Scientific Name
Sulfur (S)
Atomic Number
16
Atomic Weight u
32.06
Elemental Group
Meso elements (Ca, Mg, S ) | Secondary macronutrients
Available Forms

Available forms of Sulfur (S) for use in Pot and Bedding Plants

  • Elemental sulfur (S⁰) – slow-release, used in granular or powder form; requires microbial oxidation to become plant-available.
  • Gypsum (CaSO₄·2H₂O) – provides both Ca and S; moderately soluble, mainly used in substrate amendment.
  • Magnesium sulfate (MgSO₄·7H₂O, “Epsom salt”) – soluble, provides Mg and S; rapid correction via foliar or substrate application.
  • Potassium sulfate (K₂SO₄, “Sulfate of potash”) – soluble, supplies both K and S; commonly used in fertigation.
  • Ammonium sulfate ((NH₄)₂SO₄) – soluble, provides both N and S; good for quick substrate correction.
  • Sodium sulfate (Na₂SO₄, “Glauber’s salt”) – soluble, less commonly used in horticulture; can correct S deficiency.
  • Chelated sulfur compounds – specialized foliar products providing rapid S uptake in acidic or high-pH media.
S deficiency in Pelargonium
Image Source: LVG Heidelberg (D), care of ICL

Sulfur (S) Deficiency in Pelargonium (Geraniums) - Pot and Bedding Plants

Symptoms

  • General chlorosis (yellowing) of younger leaves first (unlike N deficiency which starts in older leaves).
  • Leaves may appear pale green to yellow, sometimes with a reddish or purplish tinge on veins or petioles.
  • Stunted growth and reduced branching, plants look spindly.
  • Flower initiation and development delayed → fewer and smaller blooms.
  • Severe deficiency can lead to thin, brittle stems and poor canopy coverage.

Causes

  • Low sulfur availability in substrate: common when soilless media with little organic matter are used.
  • Use of high-purity fertilizers (e.g., calcium nitrate, potassium nitrate) with little or no sulfate.
  • Leaching in containers due to frequent irrigation.
  • Low atmospheric sulfur deposition (decline in industrial SO₂ emissions has reduced background sulfur inputs).

Correction

  • Apply sulfate-based fertilizers, e.g.:
  • Magnesium sulfate (Epsom salts)
  • Potassium sulfate
  • Ammonium sulfate (if extra N is also required)
  • Foliar sprays with magnesium sulfate (1–2 g/L) can provide rapid but temporary relief.
  • Adjust fertigation to include balanced S sources (e.g., 20-20-20 with sulfate form).

Prevention

  • Regularly incorporate S-containing fertilizers in the nutrient program (avoid exclusive reliance on nitrate salts).
  • Use complete water-soluble fertilizers with at least 50–75 ppm S.
  • Monitor substrate solution (EC & ion analysis) to confirm adequate sulfur (target: ~50–80 ppm S).
  • Avoid excessive leaching that strips sulfates from container media.
  • Maintain balanced Ca:Mg:S ratio to prevent antagonisms.