4 Leaf Symptoms Every Hydroponic Grower Should Understand

Hydroponic growing is an art and a science, and when things go wrong, the first signs usually show up in the leaves. In this post, we’ll explore four crucial terms every hydroponic grower should know to diagnose plant health issues quickly and accurately: chlorosis, senescence, abscission, and necrosis.

These symptoms often point to nutrient deficiencies, environmental stress, or disease—and knowing what to look for can save your crop.

1. Chlorosis: When Leaves Turn Yellow

Chlorosis is the yellowing of plant leaves due to a loss of chlorophyll. It’s one of the most common signs of nutrient deficiency in hydroponics.

Causes of chlorosis include:

• Nitrogen deficiency – typically causes yellowing in older leaves.
• Iron deficiency – often affects newer, young leaves and may result from high pH levels.
• Magnesium or sulfur deficiency – also common in hydroponic systems.

Tip: Always monitor your pH and nutrient levels to prevent these deficiencies.

2. Senescence: Natural Browning and Leaf Death

Senescence is the process where leaves turn brown and die, often as part of a plant’s natural aging cycle. However, stress can accelerate it.

Triggers of senescence:

• Dry growing media – leads to premature aging.
• Excessive fertilizer (high EC) – stresses the plant.
• Improper additive use – can overload the plant with nutrients.

Real-World Warning: Many growers using new, high-EC nutrient products in the UK are reporting increased leaf senescence.

3. Abscission: When Leaves Fall Off Suddenly

If your plant’s leaves are green but suddenly drop off, you’re likely dealing with abscission. This is often caused by a surge in ethylene, a plant hormone.

What causes ethylene build up?

• Flooding or poor oxygenation in the root zone.
• Sugary additives that boost microbial activity and reduce oxygen.
• Root damage or compaction – leading to stress-induced leaf drop.

Pro Tip: Ensure good drainage and avoid overwatering to prevent abscission.

4. Necrosis: Blackened Leaf Tissue

Necrosis is the blackening or death of plant tissue. It’s most commonly caused by calcium deficiency, especially in crops like tomatoes, lettuce, celery, and even beans.

Common necrosis symptoms:

• Blossom end rot in tomatoes.
• Black heart in lettuce and celery.
• Dark spots near midribs in other leafy greens.

Other causes of necrosis:

• High humidity reducing calcium transport.
• Plant immune response to diseases like chocolate spot (Botrytis fabiae) in beans.

Solution: Use calcium-rich nutrients (e.g., Gold Leaf or Liquid Gold) and ensure consistent watering.

Final Note: Understanding Plant Hormones

A quick clarification on plant hormones: ABA (abscisic acid) was once thought to control abscission but actually promotes root growth during drought stress. Ethylene is the true hormone responsible for leaf drop.

Understanding plant stress responses at the hormonal level helps you make more informed decisions about your hydroponic setup.

Summary

By recognizing and understanding chlorosis, senescence, abscission, and necrosis, you can:

• Quickly diagnose nutrient deficiencies.
• Prevent long-term damage to your hydroponic crops.
• Improve yields through timely interventions.

Article by Dr Russell Sharp

If you would like to keep up to date with subjects just like this, you can listen to both our podcasts! Links can be found bellow:

Hydroponics Daily Podcast: https://open.spotify.com/show/207T7p7fw9sPjINfSjVXW2

Cereal Killers Podcast: https://t.co/eSEbBkTVHl