January 3, 2009

1 - Salt accumulation in potting soil damages house plants.

Yard and Garden January 3, 2009


My wife's beautiful ivy plant is not so beautiful anymore. The tips and edges of the leaves are turning black and dying while the rest of the leaf remains green. What is wrong? Can I save it?

- Mr. J.



While a disease is a possibility, mineral salt accumulation in the potting soil and salt burn of the leaves is a more likely culprit. Your NMSU Extension Service County Agent forwarded a picture of your plant to me and I did not see a water-soaked boundary between the black mark on your ivy leaves and the green portion of the leaf. That causes me to be more confident that the problem is the accumulation of minerals in the potting soil.

Each time you water you add more than water, there are minerals dissolved in the water. These may be from fertilizer you have added, or naturally occurring minerals that are common in New Mexico water. Sodium salts may be present and they cause problems quickly. Calcium salts are very common and build to higher levels before causing problems. It is possible to have your water tested to see what mineral salts are dissolved in the water, or you can ask your municipal water supplier for that information (they must test the municipal water supply periodically). In the case of these salts the knowledge of which salts are present are not critical, but management of the accumulation of salts is important. You have probably heard that you should water until water drains from the bottom of the pot. That is so that surplus salts are "leached" from the soil. This removes some, but not all of the salts. Leaching delays the ultimate solution which is repotting with fresh potting soil. Leaching is not effective if the potting soil has dried too much. So, when you are irrigating potted plants, it is good to apply a little water several times (over a period of one or more hours) to moisten the soil (and dissolve surplus minerals) before a final watering that provides surplus water to wash the dissolved salts from the pot. Do not let this water be reabsorbed into the potting soil.

Based on the picture of your plant sent to me by your County Agent, you need to repot your ivy into a clean pot with fresh potting soil. After repotting, water a little less than before until the plant has become established. After the plant has established, begin watering as described above to slow the accumulation of minerals salts and the development of salt burn in your plants.

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.

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

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