Why Won't My Orchid Bloom?

Photo of Vanda Pat Delight, a gift from my friend Jose Exposito of Soroa Orchids.

It blooms reliably for me two times a year and needs full sun.

Do you have one of those orchids that you bought in full bloom and now never seems to bloom even though you've been growing it for years and give it plenty of attention? Are you ready to throw the orchid into the compost pile? Just hold on a minute...I may have the answers to your problem. I started asking some expert growers that I know about the possible reasons that may cause an orchid not to bloom. Listed below are some of the common reasons. Before we get to those, it's important to understand plant biology. All plants bloom for reproduction, i.e., flowers get pollinated and produce seeds. It takes energy to produce flowers and seeds, so a plant will only bloom when it has excess energy. In orchids, an indication of energy is the size of the pseudobulbs for sympodial orchids or leaf span for monopodial orchids. You should strive to have progressively larger pseudobulbs or leaf span with each growth.

• Insufficient light. This is the most common reason why orchids do not rebloom. Try giving the plant brighter light levels. This boost in light intensity causes an increase in energy production. If the orchid is getting sufficient amount of light then one or more of the following may be the reason.
• Need repotting. When was the last time you repotted the orchid? Orchids need to be repotted regularly because the potting media breaks down and turns sour. Sphagnum moss breaks down more readily and should be repotted every six months, while bark breaks down slower and should be replaced every 2 years. Phalaenopsis like to be repotted in fresh media as this will invigorate them.
• Temperature differential. Some orchids such as phalaenopsis and dendrobiums need a 15 degree temperature differential between day and night, which signals a change in the season, particularly in the Fall.
• Not pot-bound. Some orchids like dendrobiums, encyclias, and epidendrums prefer to be pot bound before they will bloom. I had an Epi. Green Hornet that I repotted and kept in a 4-inch pot. It took 8 years for it grow and fill the pot before it bloomed.
• Disturbed