You may be surprised to know that chlorine is an important nutrient in plants. It plays a key role in splitting water to produce oxygen during photosynthesis. Chlorine also controls osmosis and the opening and closing of stomata.
Besides those important tasks, chlorine regulates the rate at which plants take up most other nutrients, and thus plays a role in crop yield and quality. Some experts believe that this nutrient-regulating role may also give chlorine the ability to protect plants from diseases.
Plants typically have their chlorine needs met from rainwater and naturally occurring soil salts. Chlorine is also sometimes introduced during watering or irrigation.
Chlorine deficiency is quite rare. However, chlorine may leach from the soil if plants are watered excessively, particularly on sandy soils with insufficient organic mater. Excess nitrogen, boron, sulfur, or mulybdenum may interfere with chlorine uptake.
Symptoms of chlorine deficiency include:
- Reduced growth.
- Leaf curl.
- Bronzed or mottled leaves.
- Leaf death.
- Absence of normal smell in cabbages.
- Short but highly branched root system, often with stubby tips.
In the rare event that you should see these symptoms, consider boosting organic matter levels in the soil and cutting back on the water. Also consider soil testing to find out if there are any other nutrient imbalances.
Chlorine toxicity is much more likely to occur than chlorine deficiency. Toxicity can occur naturally in arid regions where there is a buildup of soil salts due to insufficient rainfall. In other parts of the United States, the problem is usually a specific pollution source:
- Chlorinated water.
- Swimming pool runoff.
- Winter road treatments.
Symptoms of chlorine toxicity include:
- Reduced growth.
- Small, thick, bleached-looking leaves.
- Mottled yellow conifer needles.
- Leach scorch, starting with the margins of older leaves and progressing throughout the plant.
- Premature leaf shedding.
- Conifer needle death.
- Reduced storage life of potatoes.
- Plant death.
If you suspect chlorine toxicity in your plants, address the source of contamination and thoroughly flush the soil with unchlorinated water. Working gypsum into the topsoil will also help reduce chlorine buildup.