by Byron and Laurelynn Martin
Orchid flowering is induced by cultural and environmental stimuli, which occur cyclically throughout the year. Many have a regular flowering cycle of bud initiation while others can re-flower off the initial flowering spike. Certain Phalaenopsis are a good example of orchids that re-bloom off old flower spikes.
Whether blooming or re-blooming an orchid, you first must have a healthy plant and a healthy root system. To determine a healthy root system, we look at the vigor of the plant. Are the leaves shiny and not shriveled? Is the newest pseudobulb (on orchids like Cattleya or Oncidium), plump and not shriveled? This would indicate that the plant is taking up water, and thus has an active root system.
Visually inspect the roots. Look at roots on top of the pot to see if they are alive and succulent. Live roots will be fleshy if nicked. Dead roots will be brown inside showing dead tissue.
Generally, when orchids lose their roots, desiccation occurs on the older leaves and the main bulb starts to shrivel. Please note that bulbs can also shrivel with inadequate watering and this can be remedied by increasing your watering.
Next, it's important to understand the environmental mechanisms to stimulate flowering and bud formation. Many times flower initiation starts months before you see the bud. For example, Cattleya orchid bud formation is held within the sheath months before the flowers actually appear. The size and number of blooms are determined by the strength of the previous year's growth.
There are three important factors to understand the flowering mechanism, within a particular genius:
2. Light Intensity
3. Day Length
Temperature - The mechanism of temperature is seen in the way that Phalaenopsis orchids bloom. In its native habitat of the jungles, Phalaenopsis (Phals or Moth) orchids flower seasonally. They are mid-canopy epiphytes that grow in the trees under some shade. During the rainy season, cloud cover comes over the jungle and the temperatures are warm and plants are actively growing. When the dry season approaches, the temperatures drop at night as the sky opens up and the plants get an increase in light.
So when growing Phalaenopsis orchids in the home environment, try to mimic its natural conditions. During the summertime, they often have 70ºF temperatures at night. When fall approaches (much like the dry season) we need to put our orchids into a cooler spot for several weeks to a month to stimulate flowering. Keep your orchids in this cooler place (60ºF at night) until you see flower spikes emerging or buds forming on old spikes. Phalaenopsis are not high light orchids but they still need good quality light, like an east or west window.
Light Intensity - Many orchids grow in the upper canopy of the jungles: Cattleyas, Dendrobiums and Oncidiums. If you look at their natural habitat, these orchids get some direct sunlight during the day that dapples through the tree canopy. Although there are other mechanisms that initiate bloom, one of the most important mechanisms is light intensity. These particular orchids don't flower well in shade but need high light to cause the leaves to appear slightly yellow. Under shade, the leaves will be dark green. With increased light, the leaves will lighten up and even get a little yellow. This is normal and a good indicator that they are getting enough light. With good quality light, the plants put on new growth and flowering will follow.
Day Length - Some orchids, especially Cattleyas, will flower seasonally off the newest pseudobulbs because they are responding to thechange in day length. As day length begins to increase, the young bud sitting at the top of the newest pseudobulb will begin to develop. These are spring-blooming Cattleyas that are often sold for Valentine's Day or Mother's Day.
Lastly, it's worth mentioning that some orchids like deciduous Dendrobiums initiate flowering on dry stress. In this case, the plant that grew in the wet summer is subjected to a dry season that goes on for months. The plant will drop its leaves and shrivel some and then the buds will form along the stem. When encountering this type of orchid, the water is totally restricted until the buds are visible. It seems harsh but the plants need this restriction of water for growth and flowering.