Dr. Bob Gilbert
It is amazing what you can find at a grocery store – things you were not searching for and especially things you do not know you really needed. Blooming potted plants always catch my attention. Almost always there are Moth Orchids or Phalaenopsis for sale. I do get a little unnerved by the plants that have been soaked in food coloring that changes the flower color to unnatural ones like blue or orange. Remember they used to do that with carnations?
About four years ago I found among the grocery store Phalaenopsis some brightly colored blooming Oncidium (on-sid-ee-um) orchids. That reminded me about a birding trip in Guatemala. On one of our daily travels the van driver spotted a fallen clump of blooming yellow oncidiums laying along the road side. He speculated that it was probably dislodged by a troop of spider monkeys jumping from one tree to the next. He picked it up to show us that it was attached to a tree branch. It is classified as an epiphyte meaning it uses a host branch only for support. The roots do not penetrate into the branch looking for food. It is self-sufficient. It also can attach itself to rocks and is then referred to as a lithophyte, a plant that grows on rocks.
These grocery store Oncidium orchids had blooms in various colors as well as yellow. Also, I was a little puzzled that they were offered for sale as most often grocery store plants are easy to grow. These looked special. I got curious and looked at a plant label to learn they are called Oncidiums Alliances or Dancing Lady Orchids. As it turns out Oncidiums’ reproductive anatomical parts make it easy to hand-manually cross pollinate it with other orchid species creating a large alliance of related plants. One list I saw had over 300 named alliances. This explains the wide variety of bloom colors and shapes.
One characteristic of an Oncidium bloom is a swelling or callus on the lip of the lower petal. Its name comes from a Greek word “onkos” meaning swelling. I am not sure how you get oncidium from onkos? The alliances come in shades of yellow, red, white and pink with ruffled petal edges. I often wondered why they were found with Phalaenopsis’ at the store. I have since learned that their growing requirements are very similar to Phalaenopsis which is a fairly easy orchid to grow at home and whose blooms can last a long time.
Phalaenopsis and Oncidiums do well in residential temperatures of 75-78 and a little cooler at night. They both grow well in small to medium size fir bark as the main growing medium. There are dozens of soil recipes with various other materials added to the mix. You can even find already mixed bags of soil for Phalaenopsis at the big box stores which would work for Oncidiums as well. It is usually recommended to water once a week or when the soil is beginning to dry. Some people put on the soil surface an ice cube once a week. It takes some experimentation to find the right amount of light. They will not tolerate full sun or heavy shade. Oncidiums perform best in a brighter environment than Phalaenopsis. Your house is different than mine so your east facing window sill just might be the ideal site. There are numerous orchid fertilizers on the market. I think the safest thing to do is to fertilize once a month with a half strength solution. This way the plant cannot be burned from too much fertilizer.
Keep in mind the grocery store really is not interested in selling you something that will die as soon as you get it home. So, they offer easy and attractive plant materials that have a good survival rate for average conditions and for the average gardener. Look what happened to my Oncidium Alliance plant after four to five years. Although I have a greenhouse, I am convinced you can accomplish the same with just a little thought and effort at home. Also, from the photo you can see why Oncidiums are sometime classified as spray orchids and have the common name Dancing Ladies. With a little breeze the flowers sway as if it is dancing. My plant has just finished blooming after four months of display. I divided it into four big clumps. Next time it blooms I will have a chorus line of Dancing Ladies that will not have a “hole in their stockings or their knees won’t be a’knocking.”
Dr. Bob Gilbert, now living in Franklin, is co-founder of Smith Gilbert Gardens in Kennesaw, Ga.
Karen Lawrence is a professional horticultural and wild life photographer from Franklin.