Not Enough Difference between Day and Night Temperatures
The most common reason that orchids don’t bloom indoors is that the environment doesn’t have enough of a change in temperature between day and night. In orchids’ natural habitats, evening temperatures are at least 10°F to 15°F lower than the daytime temperatures. This temperature difference triggers the orchids to start developing flowers. In many home environments, the temperature doesn’t vary much between day and night.
Get yourself a maximum-minimum thermometer and place it in your growing room. This thermometer will tell you if you need to move the plant somewhere cooler in the evening, like closer to the window.
If you summer your orchids outdoors during the summer,you’ll easily be able to provide this temperature difference. The temperature in my orchid summering area outdoors drops in the evening at least 15°F and sometimes 20°F or more during late summer and early fall.
Too Moist during the Winter
Several orchids, like some of the dendrobiums, require a very dry period, up to several weeks, during the winter, when very little water should be given to the plants. This mimics their native habitat, in which their winters are dry. This dry period triggers flower buds to form. Then when watering or natural rainfall begins in the spring, the buds are ready to swell and produce flowers.
Too Little Light
If the leaves of your orchids are very dark green, the new growth is longer or “stretched” compared to the older growth, and the leaves on the stems are farther and farther apart, these are signs that your orchid is not receiving enough light. Orchids will survive in this lower light, but they won’t bloom. They need more energy from light in order to produce flowers.
If your orchid is displaying these symptoms, gradually increase its exposure to light by placing it in a brighter window or moving it closer to florescent lights.
Excessively High or Low Temperatures
Excessively high or low temperatures can either prevent buds from forming or can cause the buds that are starting to develop to shrivel and fall off. Unfortunately, flower buds are very vulnerable to any forms of environmental stress, and they react to this stress by falling, shrinking, and drying up before they open.
When orchids are shipped in cold weather, the low temperatures that they experience in transit can cause them to drop their buds. When you buy orchids during the winter that have been shipped to the store, wait until they’ve been in the store for a day or so to see if the buds have been affected by their trip.
Not Using a Fertilizer or Using One with Too Much Nitrogen
Most orchids have relatively low nutrient needs, but, because they’re usually grown in bark mixes that have few nutrients, some type of fertilizer is usually necessary to provide their basic requirements.
Applying fertilizers with too much nitrogen can also cause poor or no blooming. High-nitrogen fertilizers can stimulate lush leaf growth at the expense of flowers.
If you purchase an orchid that hasn’t bloomed, it may not yet have reached its mature size. The amount of time it takes for an orchid to mature varies a great deal depending on the type of orchid. For instance, moth orchids are very fast to mature, while some of the others may take years. Plants that have not yet bloomed are usually sold as seedlings (which can take several years to reach maturity), as NFS (near flowering size, which usually bloom within a year), or as FS (flowering size, which means they’ve reached mature size and will usually bloom within several months).
Too Low Humidity
If the air is too dry when the buds are forming, they’ll sometimes dry up before they open. To prevent this from happening to your orchids, keep the humidly in your growing area at 60 percent or greater.
Disease, Insects, or Mice
Orchid buds that are ravaged by insect pests or attacked by diseases will either shrivel in place or, when they open, be deformed.
Some chemical pesticide sprays that you may use on insects and disease can cause damage to the flower buds, so be careful to spray-test a few buds at first before you apply the material to the entire plant. If possible, wash the bugs off with warm water instead of applying chemical sprays to the buds.
Mice also have the annoying habit of waiting until the flower buds are plump and just ready to open before they decide to make a meal of them. If your flower buds just disappear one night, suspect mice as the likely culprits.
Not Enough Water
When flower buds are starting to swell, their cells are filling up with water like a balloon. If sufficient water is not available to the developing buds when all this is happening, they won’t fully develop and instead will shrivel and never recover.
Cold water can also have the effect of causing the buds to drop off before the flowers open. To prevent this, use water that is room temperature or slightly warmer.
Recently Transplanted and Divided
When an orchid is transplanted, roots are frequently damaged, which causes stress to the plant by reducing the roots’ ability to effectively supply water to the buds.
Interestingly, after the flower is fully formed and open, transplanting and or dividing rarely does much harm. In fact, some people routinely transplant their orchids when they’re in flower, although I think you’re better off waiting until right after they flower to transplant them.
The Ten Most Common Reasons Why Orchids Don’t Bloom on what-when-how, In Depth Tutorials and Information
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By Steven A. Frowine
(www.what-when-how.com/steven-a-frowine/) or (www.members.authorsguild.net/stevefrow/bio.htm)
Other works by Steven A. Frowine
Miniature Orchids (www.members.authorsguild.net/stevefrow/miniature_orchids_77055.htm)
Fragrant Orchids: A Guide To Selecting, Growing, And Enjoying (www.members.authorsguild.net/stevefrow/fragrant_orchids__a_guide_to_selecting__growing__and_enjoying_38984.htm)
Orchids for Dummies (www.members.authorsguild.net/stevefrow/orchids_for_dummies_38975.htm)
Moth Orchids - The Complete Guide to Phalaenopsis (www.members.authorsguild.net/stevefrow/moth_orchids__the_complete_guide_to_phalaenopsis_65954.htm)
Growing Tropical Slipper Orchids Under Lights (.pdf file free to download)(www.members.authorsguild.net/stevefrow/growing_tropical_slipper_orchids_under_lights_121823.htm)
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