Issue: February 24, 2001

• Prune Christmas cacti?
• Orchid potting soil

Prune Christmas cacti?

I have a lovely Christmas cactus which was given to me two years ago. In spite of my ignorance of proper plant care, the plant bloomed beautifully both last year and again this year. It has grown quite large, and the stems at the bases of the stalks have become somewhat woody. Is that normal? Would pruning benefit this plant? I have just learned what I should have done to promote blooming and growth (thanks to the Internet) but nowhere could I find information about pruning.

I would appreciate any information you could give me about when, if, and/or how to prune.

We normally don't prune Christmas Cacti unless we want to propagate them(make new plants). It will sometimes "self-prune", that is drop some branches. This usually happens after drought stress or if it has been overwatered and the roots have been damaged. Even after stress, the plant can recover if it is properly treated.

If necessary, you can remove some of the stem segments at the end to make the plant smaller if it becomes so large that it is unmanageable. Pruning in this manner will not harm the plant. Just cut the stems between the "joints."

At the time you remove some stem segments, or if they fall naturally, it would be wise to allow some of them to root to start new plants. In time, the large plant may suffer root rot and need to be replaced. You will have a new plant ready to grow.

The woody base you described is normal and indicates a healthy plant. It is not a cause for worry.

Orchid potting soil

I have a Dendrobium orchid which is potted with bark. When the time comes, should I replace with bark or potting soil, or does it matter? Is Miracle Grow okay to use to fertilize?

The Dendrobium and many other orchids grow naturally on the bark of trees. These "epiphytic orchids" need very good drainage. That is why they are grown in the bark instead of soil. When repotting, use fresh bark (sold in garden stores for growing orchids) or a similar potting medium. Some people add lava rock to help increase drainage.

Potting soil is not recommended for this type of orchid, but I have seenpeople succeed with potting soil. It is much easier for root rot to develop in potting soils which do not drain as readily.

You might want to find an orchid society in your area and benefit from advice from orchid growers familiar with your local conditions. Members of an orchid society should be able to look at your plant to determine which Dendrobium it is, and then give advice based on that.

Regarding fertilizers, Miracle Grow(TM) is okay, as are many other houseplant fertilizers. Don't overfertilize. Too much nitrogen fertilizer will speed the decomposition of the bark and development of toxic compounds which can injure your orchid.

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.

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