Chlorine can kill a host of organisms, plant life among them. However, its danger to your plant life is tied very specifically to its amount. In tiny doses, chlorine is actually used to the benefit of plants, killing off fungi and bacteria. In more potent dosages, it can harm, kill and eradicate the plants with which it comes in contact.
Atomic number 17 in the periodic table of elements and chemicals, chlorine -Cl2- is a yellow-green gas at room temperature. It has a density that is 2.5 times greater than air and 1.5 times greater than water in its liquid form. Chlorine does not exist in nature except in combination with other chemicals and is extracted through a process of electrolysis. It is an irritant to skin, eyes and lungs, and just a few breaths of the gas can kill.
Chlorine is both a poison and a panacea for its ability to kill. Added to drinking water, it kills harmful bacteria to assure your water's safety for consumption. It's also the reason your backyard pool doesn't make you sick when you swim and why your white laundry stays white. Chlorine is a disinfectant and an antiseptic. It is used in the production of paints, paper, plastic, pharmaceuticals, insecticides, textiles and dyes. It is a part of your everyday life, but in its purest form, it remains a dangerous chemical that must be used with caution.
Named as a distinct element in 1810, Chlorine was added to water supplies to prevent the spread of water borne illnesses like cholera and typhoid. By the beginning of the 20th century, chlorine was used as the primary disinfectant for U.S. water systems. Throughout its history, chlorine has been used positively to forestall major epidemics. However, it also has been used as an agent of warfare. During World War I, chlorine gas was one of the first chemical weapons ever used.
Chlorine and Plant Life
While a diluted mix of chlorine bleach and water is often used to kill fungi, mould and bacteria on bulbs and plant roots, straight chlorine will kill plants. A little chlorinated water slopping over a pool's edge is unlikely to kill the surrounding grasses. The chlorine is diluted by the water, and the soil acts as a further filtration system. However, straight chlorine in liquid or tablet form will kill plants. Chlorine kills essential bacteria needed for plant growth and also interferes with the cellular function of plants, killing them outright.