Understanding and Solving pH and Nutrient Lockout in Arum and Calla Lilies

Nutrient lockout occurs when a plant cannot take up nutrients via its roots, resulting in nutrient deficiencies, stunted growth, and, in extreme cases, the death of a plant. The signs of nutrient lockout are the same as those of a nutrient deficiency, mainly discolored foliage and stunted growth. With nutrient lockout, however, the nutrients a plant needs are present—the plant simply isn’t able to absorb them.

What Causes Nutrient Lockout?

Nutrient lockout can have several causes, including:

• pH Imbalance: pH imbalance is the most common cause of nutrient lockout. Nutrients are only available to plants at certain pH levels, so when the pH of a plant’s soil, water, or feed falls or rises above the ideal range (for arum and calla lilies, that’s 5.5–6.5), the plant is unable to take up nutrients via its roots, even if they are present.
• Overfeeding: Overfeeding can cause salt or excess nutrients to build up around a plant’s root zone, interfering with a plant’s ability to feed properly.
• Nutrient Imbalance: Poorly prepared fertilizers or soils with nutrient imbalances can decrease the availability of nutrients to plants, causing lockout.
• Overwatering: Overwatering can contribute to the buildup of salt and other minerals in a plant’s medium, which may cause nutrient lockout.

Signs of Nutrient Lockout

Nutrient lockout causes nutrient deficiencies, which typically produce symptoms such as:

• Discoloration, such as yellow or rusty, spotted leaves. Some nutrient deficiencies may also cause purple or red stems.
• Curled, twisted, or otherwise distorted leaves.
• Stunted or abnormal growth.
• Dying leaves.

How to Fix Nutrient Lockout in Arum and Calla Lilies

To address nutrient lockout in arum and calla lilies, you need to identify the underlying cause and correct it. Here’s how to do it:

1. Check pH Levels: Start by measuring the pH of your water, nutrient solution, and soil. Use a pH meter or test kit to ensure the pH is within the ideal range of 5.5–6.5. If the pH is outside this range, adjust it using pH up or pH down solutions.
2. Measure EC Levels: Use an EC meter to measure the electrical conductivity of your water and runoff. For arum and calla lilies, the EC should be between 2.0 and 3.0 dS/m. High EC indicates excess nutrients, while low EC suggests nutrient deficiency.
3. Flushing the Medium: If you find that the pH or EC levels are not within the desired range, you need to flush the medium. Here’s how to do it:
   • Lowering EC: If the EC is too high, flush the growing medium with pH-adjusted water (within the range of 5.8-6.2) to help bring down the EC. Continue to flush until the runoff EC matches the desired range of 2.0-3.0 dS/m.
   • Raising EC: If the EC is too low, you can increase it by adding a water solution with the desired EC rating. Carefully monitor the runoff and adjust until it reaches the appropriate level.
4. Adjusting pH Levels: If the pH is too low (below 5.5), flush the medium with water adjusted to a higher pH (around 6.8-7.0) until the runoff is within the desired range of 5.8-6.2. If the pH is too high (above 6.5), flush with pH-adjusted water (around 5.0-5.5) until the runoff is within the ideal range.

By regularly measuring and adjusting the pH and EC in your growing medium, you can effectively manage and prevent nutrient lockout in your arum and calla lilies. This proactive approach ensures your plants remain healthy and vibrant. This is how you read, measure, and adjust pH and EC in your medium to fix the problem of nutrient burn or pH lockout.