Shriveling Christmas Cactus

Question:

My Christmas Cactus is shriveling, and I am afraid that it will die. What is wrong, and what can I do?

Answer:

This is not an uncommon problem. The plant has received too little water or has had something kill its roots. Root loss may be due to overwatering or salt accumulation in the potting soil.

Sometimes a houseplant that is watered frequently will dry out and suffer desiccation because the soil does not get moistened when water is supplied.

This occurs when the soil cracks or pulls away from the side of the pot so that water just runs through the cracks or around the soil. When the water passes through the pot rapidly, the soil doesn't absorb the moisture and the plant dries out.

If the soil stays too wet, especially in the case of a succulent plant such as the Christmas cactus, the roots are very likely to decompose. Without an active root system, the plant shrivels for lack of water.

In New Mexico, and other areas with high levels of salts (calcium, sodium, or other salts) in the water, salt accumulation in the potting soil can cause damage to the root system. Again, this results in a shriveled plant.

All of these are possible causes of the shriveling that you described. You will need to determine which is the most likely cause under your growing conditions. Have you been keeping your Christmas cactus very dry, or is the soil cracked or pulled away from the pot so that water runs quickly through the pot? Does the potting soil stay soggy for several days between waterings? Is there a salt crust developing on top of the soil or around the edge of the pot? Once you identify the source of your problem, you can work to remedy it. In all cases, repotting will help. Replacing the soil will eliminate the cracks and allow better water absorption. Repotting will replace the salty soil with fresh soil. By choosing a potting soil with a high sand content, you will increase drainage and prevent water logging.

If the problem is due to lack of water absorption as water rapidly runs past the soil, it is possible to moisten the soil by placing the pot in a dish pan of water so that water may be slowly absorbed into the soil. Once the soil is moist, however, allow the surplus water in the pot to drain away. This draining is important, whether you water from the top or the bottom, to slow the accumulation of salt in the soil. As water drains from the soil, some of the excess salts are washed away.

When you are preparing the potting soil, consider the fact that the Christmas cactus is a true cactus but not native to the desert. It is native to the tropical rain forest where there is frequent rain in the rainy season and a definite dry season. Even though there is rain every day for part of the year, the roots of the Christmas cactus dry rapidly because this unusual cactus grows in compost formed from decayed leaves in the branch crotches of trees. This location high in the tree allows the water to drain away rapidly, so the roots are never soggy for very long. This is the type of condition you want to create in the soil you use in our pots— a soil which is high in organic matter to hold moisture, but one which drains rapidly and doesn't remain soggy. Addition of sharp sand to potting soil allows us to create such a soil.

Please join us on Southwest Yard & Garden, a weekly garden program made for gardeners in the Southwest on: KNME-TV Albuquerque at 1 p.m. Sundays, KENW-TV Portales at 10 a.m. Saturdays, and KRWG-TV Las Cruces at 10:30 a.m. Saturdays (repeated at 11 p.m. Sundays and 1 p.m. Thursdays.)

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.

Links:

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

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