Issue: May 17th, 1999

Water softener bad for plants

Is it true that water from my water softener is damaging my plants? A friend told me that the reason I can't grow houseplants is because I have a water softener.

Your friend may be correct. While there are many factors which make growing houseplants difficult, softened water can indeed be a cause of problems. If your water softener replaces calcium and other "hard water" minerals with sodium, a common means of softening water, then it is indeed causing problems when you water your plants with that water. Sodium, though needed by some plants in very low amounts, is toxic to plants at slightly higher concentrations. As you water the plant and the water is used by the plant, the sodium enters the plant. As the water evaporates from the soil, the sodium concentrates in the soil. Over time, the concentration of sodium causes the problem to get worse as sodium levels increase.

There are potassium-based water softening systems which may cause less problems. In these systems the hard water minerals are replaced by potassium, a plant nutrient that is beneficial to plants. However, as the potassium accumulates in the potting soil, it too can reach levels which are damaging. Potassium can accumulate to higher levels before the problems develop. Proper leaching of salts (potassium and other salts) from the potting soil frequently, and repotting before injury occurs, are ways to have softened water and avoid the problems.

There are other methods of removing hard water minerals from soil. As long as plant toxic minerals are not added to the water, they should cause no problems.

In many cases the easiest solution is to just use water from a faucet that receives unsoftened water. In New Mexico ground water usually has high mineral content, but only in some areas is the content high enough to cause plant injury. However, leaching the salts from the soil on a regular schedule is important.

Drought still?

Now that we had so much spring rain, are we still concerned with drought?

From discussions I have had with others interested in the water situation in New Mexico, the answer is "Yes, we are still concerned with the limited water available in New Mexico."

The lower than usual snowpack in the mountains means that there will be less water available in the rivers and streams. This will also reduce the recharge of water in many of our underground aquifers. If the above average precipitation continues through the summer, it would be nice but would not change the fact that there is reduced snowpack. It would not remove the concerns regarding the drought.

It is always important to remember that New Mexico is in an arid geographical region. Even moist years are dry by the standards of many other states in the country. We must always manage our water carefully.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!