How to Balance pH for Pelargonium Plants

Maintaining the optimal pH range of 5.8 to 6.4 is crucial for the healthy growth and development of Pelargonium plants. If the pH drops below this range, it can lead to lower leaf chlorosis and necrosis due to increased availability and uptake of iron (Fe) and manganese (Mn), causing Fe and Mn toxicity. To prevent this, it is essential to monitor the pH and soluble salts (electrical conductivity or EC) of the substrate and make necessary adjustments.

Monitoring pH and EC

To determine the pH and EC of the substrate, you can use the following methods:

  1. In-house 1:2 Dilution
  2. Saturated Media Extraction (SME)
  3. PourThru procedure

These methods will provide similar pH values, but the EC values may vary. Ensure that your pH and EC meter are working correctly and calibrated regularly to obtain accurate readings.

Adjusting pH

pelargoniumImage source: Pixabay

If the pH is below the optimal range, you can quickly adjust it using the following methods:

Flowable Lime or Hydrated Lime

  1. Mix 1 lb. of flowable lime or hydrated lime in 3 to 5 gallons of warm water.
  2. Let the mixture settle, and then decant the liquid.
  3. Apply the liquid through an injector at a ratio of 1:15.

Potassium Bicarbonate (KHCO3)

  1. Use 2 lbs. of potassium bicarbonate per 100 gallons of water.
  2. Rinse the foliage immediately after application.
  3. Leach heavily the following day with a complete fertilizer to reduce substrate EC and restore nutrient balance.

Note: Be cautious when using potassium bicarbonate, as rates greater than 2 lbs. per 100 gallons of water can cause phytotoxicity. Additionally, raising the pH above 6.0 is best for zonal geraniums when dealing with iron and manganese toxicity.

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Maintaining Optimal Conditions

To ensure the long-term health of your Pelargonium plants, consider the following factors:

Temperature

Pelargonium plants thrive in temperatures between 65°F and 75°F (18°C and 24°C) during the day and 55°F to 65°F (13°C to 18°C) at night.

Watering

Water Pelargonium plants when the top inch of the soil becomes dry. Avoid overwatering, as it can lead to root rot and other issues.

Fertilization

Use a balanced, water-soluble fertilizer with a ratio of 20-20-20 or 15-15-15 and apply it at a rate of 200 to 300 ppm nitrogen (N) every 7 to 14 days.

Leaching

Regularly leach the substrate with clear water to prevent the buildup of soluble salts and maintain a healthy root zone.

By following these guidelines, you can effectively balance the pH for your Pelargonium plants and ensure their optimal growth and development.

References:

pelargonium 2Image source: Pixabay

  1. Whipker, B.E., J. Henry, and W.G. Owen. 2018. Corrective Procedures for Modifying Substrate pH and Electrical Conductivity (EC). e-GRO Alert 7(2):1–5.
  2. Catlin, Nora, et al. “Geraniums: Diagnosing Nutrient Disorders.” e-GRO Alert, 2017, pp. 1–10.
  3. Abedini Aboksari, H., et al. “Application of biofertilizer for Pelargonium peltatum growth in new organic substrates.” Journal of Plant Nutrition, vol. 41, no. 1, 2018, pp. 137–149.