Caring for Houseplants: Orchids and Christmas Cactuses
January 9, 2021
Reprinted Columns from 2001 and 2002 written by Dr. Curtis Smith
Perhaps more than any other time of year, in January, Cooperative Extension Service Agents receive all sorts of questions about houseplants. This week I’ve selected a few archived columns with tips that still ring true twenty years later. Dr. Curtis Smith—who authored these reprints—is the former Extension Horticulture Specialist for New Mexico State University and continues to teach and inspire. Archived columns are available at https://aces.nmsu.edu/ces/yard/archives/.
Pruning Your Christmas Cactus
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?
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."
When 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.
Orchids in Potting Soil
I have a Dendrobium orchid potted with bark. When the time comes, should I replace it 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 seen people succeed with potting soil. It is much easier for root rot to develop in potting soils that 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 over-fertilize. Too much nitrogen fertilizer will speed the decomposition of the bark and development of toxic compounds that can injure your orchid.
Removing Old Bloom Stalks on Orchids
I want to prune the stalk of my orchid now that the blooms have fallen off. The stalk is very long and difficult to deal with, but I am not sure how to properly cut it back. Will I kill the plant if I cut it back too much?
Pruning an orchid blossom stalk should cause no harm to the plant. However, some orchids will produce new bloom shoots from the nodes on the old blossom stalk, or some plants will produce small baby plants from these nodes. The new plants may be removed and potted after they develop roots. Of course, some orchids do neither of these things. In either case, it doesn't hurt the plant if you remove the old bloom stalk; you may just miss some new blossoms or a baby plant.
Once the stalk turns yellow or brown, it is obvious that no blossoms or plants will be produced. You can then cut it to within an inch from where the blossom stalk originated on the plant. You can also cut it there when it is green if you don't mind losing potential blossoms. Another option is to just remove the end of the blossom stalk to shorten the stalk but retain enough so that it may bloom again. If you do this, cut it back to about 1/4 inch above a node (indicated by a small leaf-like bract clasping the stalk).
Enjoy your orchid.
Visit our 25 years of NMSU Southwest Yard & Garden column archives.
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: firstname.lastname@example.org, office: 505-865-7340, ext. 113.
Please copy your County Extension Agent and indicate your county of residence when you submit your question!