Will it help or harm plants?
For any garden, hard water can raise soil pH levels, increasing alkalinity. Since desert soils tend to have higher than average pH ranges, raising the alkalinity may have adverse effects, especially on non-native or non-adapted plants.
Minerals such as calcium carbonate and magnesium carbonate influence water hardness. Since these two minerals are the components of limestone, using hard water to irrigate gardens is the same as adding small amounts of lime to your soil every time you water.
Although rain will generally dilute the buildups of these minerals in the soil, desert gardeners can’t depend on sparse rainfall.
The pH –raising effects of hard water are more pronounced when used on container plants or when irrigating through overhead sprinklers. Hard water sprinkled over plants can leave white, scale-like residue on leaves and stems when the water evaporates.
Increases in soil pH levels, along with calcium and magnesium carbonate deposits can be unhealthy for young leaves, especially with acid-loving plants. The leaves can turn yellow and pale, while the veins in the leaves stay green. This is known as lime-induced chlorosis. While it won’t kill the plant, it will make it unhealthy, reduce its vigor and lower its immune system, making it more susceptible to other diseases and to insects.
Hard water can also clog drip irrigation systems.
The only way to tell if your water is hard is to test it.
There are easy-to-use water testing kits available, but most agricultural universities in North America maintain water-testing services. Contact your local cooperative extension service or master gardening association for specific information.
