All but one of my orchids are blooming this season! What could be the cause of the one orchid not blooming?
First of all, congratulations that you have all but one of your orchids
blooming. Orchids are plants with very particular needs, as you well know. I
have found two possibilities as to why your one orchid will not grace you with
its flowers: light and space. However, there are other possibilities as well,
which I will try to address.
Perhaps this one plant is not receiving the amount of sunlight it needs to bloom
and the others are. Are all your orchids the same species or variety? If so, are
they all in the same area of your house; i.e. same window? If they are not the
same species or variety, then they may require different amounts and levels of
intensity of light. Are they growing in a window with natural light or are you
growing them under artificial light? If you are using artificial light, orchids
do require dark as well as light. Orchids “should not receive more than 14 hours
of artificial light a day. More than that will prevent them from blooming.”
(Orchid Growing Basics by Dr. Gustav Schoser, Sterling Publishing Company, 1993)
Are you using a fertilizer? If so, and the first number is a lot higher than the
second or third (such as 15-5-5), it is likely that the plant is receiving too
much nitrogen. This will do wonders for the green leaves but nothing to promote
flowering. A fertilizer with the numbers closer together (such as 10-12-10) will
be more balanced and would be recommended. Are you monitoring the temperature?
“The effects of temperature changes are most clearly observable in the Cymbidium
orchids. Flower production begins when daytime temperatures are about 68 degrees
and nighttime temperatures are around 50-57 degrees. Phalaenopsis schilleriana
and its hybrids will only bloom when the nighttime temperature is under 68
degrees for at least 2-3 weeks.” (Orchid Growing Basics)
Here is an excerpt from a frequently asked question and answer web page from a
commercial grower: beautifulorchids.com.
Q: I am growing my phalaenopsis orchid in the house but they never bloom. What can I do?
A: The most common reason for any orchid not to bloom is insufficient light.
Move your phalaenopsis plants to a window where they will receive strong, but
indirect light (near a south-facing window is ideal). You might also try
lighting your plants with a fluorescent light fixture placed about 1-2 feet
above the foliage. Give up to 12 hours of supplemental light per day.
Phalaenopsis will also develop flower spikes in response to a cool period of
about four weeks with night temperatures of 55F. After the cool treatment, raise
the night temperature back to the normal 60-65F minimum. See if these changes to
your growing conditions help to stimulate your plants to bloom.
Another page on the same site more clearly defines good vs. bad light. They
explain that too little light may prevent the plants from blooming. They also
list specific orchids that prefer low light and those that prefer moderate to
high light.
The Brooklyn Botanic Garden All-Region Guides: The Gardener’s Guide to Growing
Orchids (2004) Handbook #178 has good information regarding light
requirements on a variety of orchids. It is noted in this book that “light is
undoubtedly the most important factor in determining whether or not an orchid
will flower.” The American Orchid Society’s page on “Light, the Key to Successful Blooming” should also be helpful.
Also, there is a possibility that the one orchid has outgrown its pot faster
than its companions and has a need for more space (and possibly more nutrients).
“Most orchids usually only bloom from new growth” (Your First Orchids and How
to Grow Them published by the Oregon Orchid Society, Inc 1988). “An orchid is in
need of repotting when the leading pseudobulb or growth has reached the rim of
the pot and there is no room for future development. (The Gardener’s Guide to
Growing Orchids by Wilma and Brian Rittershausen, David and Charles Publishers
2001) If you are getting new shoots but they are growing over the edge of the
pot and breaking off, this would also be a sign for the need to repot.
The Gardener’s Guide to Growing Orchids by Wilma and Brian Rittershausen, and The
Brooklyn Botanic Garden All-Region Guide and Orchid Growing Basics by Dr. Gustav
Schoser, offer good directions on repotting. The Schoser title even offers
recipes on how to make your own potting mixes.