Many causes of 'bud blast'
By Sue Morris and LaVonne Swart, Master Gardeners
Last week we talked about orchids, different kinds, watering needs, etc. This week we would like to cover the topic of "bud blast." That is when you watch as long-awaited orchid buds brown, die and drop instead of becoming beautiful flowers. Bud blast is when buds wither and fall from an otherwise healthy plant. There are any number of causes for this to happen. Buds are the most sensitive part of an orchid and are easily affected by unsuitable conditions in the growing environment.
Under or overwatering is a common cause. If a plant becomes too dry, it may withdraw moisture from buds as a survival mechanism. Overwatering can damage the orchid's root system with the end result of being a lack of water to the plant. When the plant is unable to absorb sufficient quantities of water, it will withdraw water from the buds, bringing about their demise. Watering with cold water can shock a plant, causing bud drop. (Thus we wonder why some producers recommend watering with ice cubes?)
Precautions can be taken to prevent bud blast. If a budding orchid receives drafts from a window, a/c or heating vent or even a rush of air from a hot oven, it may drop buds. Temperature fluctuations that occur when taking a plant in from the car or outside during hot or cold weather, bringing plants back into a heated house after a summer outdoors, or temperature extremes caused by running heating or air conditioning for only part of a day can affect the buds.
Orchid buds can be affected by fumes from paint, natural gas leaks or other chemicals. Ethylene gas given off by ripening fruit, engine exhaust, cigarette smoke, open fires, etc. can also cause bud blast. Too much fertilizer isn't good either.
Once you find a window your orchid likes, you know you have found the spot where it receives the correct amount of light. (Just like when you grow African violets). Sue keeps her orchids in a west bay window. In the summer there is a large grove of trees west of the house so it receives filtered light. In the winter once night time temperatures can get to zero or below, she removes the orchids from the bay window and keeps them on a large table next to the window so they won't receive any cold drafts. They are also further away from the sunlight that is no longer filtered by the trees.
Aphids and thrips can cause bud blast. Sue hasn't had any problems with insects on her orchids so has no experience with that. Thrips can be controlled with Diazinon or Malathion. Aphids can be removed with a cotton swab soaked in rubbing alcohol. Her suggestion would be to check with a nursery for ideas in controlling insects if they occur.
Occasionally, even under perfect cultural conditions, an orchid will continually abort buds. There may be a genetic mutation responsible for its inability to produce viable blooms and in that case the plant should be discarded.
Now we give you all this information, after telling you last week how easy orchids are to grow and care for. They really are. We haven't had many problems at all with our orchids. Just make sure your orchids never sit in water so the roots rot and don't expose them to drafts — that will take care of 90 percent of any problems you might have.
Some of this information was taken from the July 2003 issue of Orchids — The Bulletin of the American Orchid Society; www.aos.org.