Welcome to the AOS Beginner's Newsletter. We will be sending you monthly tips on how to grow orchids and help you get them to bloom again. In addition to the information presented here, we invite you to visit the AOS website at www.aos.org and check out the information found under ORCHID INFORMATION > ORCHID BASICS.
Oncidium and its Hybrids
While phalaenopsis, with their arching sprays of flowers in a line, are elegant and cattleyas, particularly the large, corsage-types, are flamboyant, oncidiums are fun. Oncidiums come in many forms and, as a result, go by various nicknames: Spider Orchids, Pansy Orchids, Dancing Ladies. An entire group of oncidiums, technically brassias, are pale green with very dark, almost black, spots on very long petals giving them a distinctly spider-like appearance. These, along with a few other oncidiums and their hybrids are pendulous, like the classic phalaenopsis. Miltonias are remarkable in their pansy-like appearance. Yellow oncidiums with large lips are called "dancing ladies" because the lips resemble skirts. Commonly available oncidium hybrids have many small to medium sized flowers in a wide range of colors, emphasizing yellows, browns and reds. Most of these are held erect on branching stems. And they tend to have lots of long-lasting flowers.
The diversity of oncidiums can be overwhelming, ranging from warm to cold growing, requiring high to low light, and some, fortunately few, requiring special care in watering. While most Oncidium hybrids are very tolerant of conditions, the species are not. Tolumnias require precise care, particularly with respect to watering, while miltonias can be finicky about light and humidity. I will not address any of these here. Rather, I'll stick to the basic requirements which apply to the widest range of plants. I will focus on the kinds of oncidiums which are easy and which are commonly available. As your acquaintance with these splendid plants grows, you will want to explore some of the more uncommon, but often extravagantly beautiful, ones.
Oncidiums are generally tolerant of an amazing range of growing conditions and treatment. They want treatment which is easy to provide in the greenhouse or average home.
Almost all commonly available oncidiums will do well in intermediate temperatures--that is above 60 F at night and below 80º F during the day. Night temperatures of 55º F and day temperatures of 85 F will be fine for most plants. If the day temperature goes above 85º F, increase humidity and air movement.
Almost all commonly available oncidiums will do well in bright, diffused light. Hold your hand 18 inches above the plants: if you see a very distinct outline of your hand, it may be too bright. If you cannot tell that you are holding your hand above the plant, it may be too dim. Plants with very thick leaves will want more light and plants with very thin leaves will want less. None of them will do well in direct sunlight.
When you water, pour it on. Then, let the plant mix dry out to halfway through the pot before watering again. A sharpened wood pencil, pushed gently down into the pot can be a good indicator: the shaved wood will darken if there is water so you can see how far down it has dried out. Thick rooted oncidiums will need less watering than thin rooted — but this "pencil test" will work well enough. Water less often in winter, when temperatures are cooler and light is less intense. If you are not sure the plant needs water, hold back.
||Oncidium Sharry Baby 'Sweet Fragrance' AM/AOS may not just be the all-time favorite oncidium hybrid, but certainly ranks among the most popular and commercially successful orchids of all time. It's "baking cookie" aroma has made a winner.
Orchids, as a group, like humidity — oncidiums are no exception. Try to keep your growing area between 30 and 60 percent relative humidity. A cheap humidity gauge will be a help. If the humidity goes too low, put your plants on on trays or saucers of gravel or pebbles and water. The pot is placed on the pebbles above the water line so the base of the pot is not immersed in water. If the humidity level goes high, increase ventilation. Air movement is good in general for oncidiums but only if the air temperature is right — don't let a cold blast hit the plants directly.
Give your plants fertilizer when they are actively growing. Liquid plant foods, approximately 20-20-20 in formulation will be fine. The amount of fertilizer needed by orchids is surprisingly low — use less than half of the recommended dose and fertilize with every other watering. In the most active growing periods, increase the fertilizer to three out of four waterings. In the winter, once a month will be fine.
Repot oncidiums when the plant fills the pot. Do this in the spring, when you see new growth. The potting mix can be almost anything but not dirt. Potting mixes for orchids, usually composed of bark with other additions, can be purchased in most nurseries. For fine roots, use a finer mix; for thick roots use a coarser mix. Learn how the mixture retains water (using the pencil method or one's finger) and adjust watering to the mixture. Repotting is easy — take the plant gently out of the old pot, gently remove loose mix, put the plant on a mound of mix in the new pot and fill in around the plant. The plant should be firmly in the pot and stand on its own.
|Bllra. Diana Dunn 'Newberry'
||Tolu. Popoki 'orchidworks.com' HCC/AOS
||Onc. My Quest 'Belle Glade' HCC/AOS
||Mtssa. Pelican Lake 'Everglades' AM/AOS
Grow with your orchids
The possibilities in color, size, and cultural requirements for oncidiums will allow you to pick and choose what you like as you gain in experience. Well established plants available at big-box outlets will be rewarding as you move toward more demanding (often species) orchids. Attend a local orchid society meeting — oncidiums are commonly grown all over the place. You'll be able to see what is growing well under your conditions and you will probably be amazed.
AOS Education Committee