Guest Author - Susan Taylor
As with any subject to do with growing orchids you will find as many different ways of feeding your plants as people you talk to. Some simply go to any store and buy whatever is one sale when they need fertilizer and use that. I've seen plants grown like this with hundreds of blooms and growing vigorously. Some people will only buy one specific type of fertilizer, carefully measure and mix with other elements in pure reverse osmosis water. I've seen plants grown this way that don't look so good and I've seen other that look beautiful. Other people will try one thing and then another without success with any of them. I have one friend who uses the same fertilizer she uses on her grass on her orchids and they grow!
The fact is that no fertilizer will keep an orchid that does not have a good growing environment growing well. It might help a little bit, but on the whole, giving your plants the right environment is much more important than giving them fertilizer. As a result of their natural growth habit, orchids require very little in the way of extra nutrition which is why the American Orchid Society coined the phrase "weakly weekly" meaning fertilize weekly at a half to a quarter recommended rate for any fertilizer.
I use an orchid fertilizer at half recommended strength and bloom booster once a month at half strength. I also add SuperThrive™ at the rate of 1 milliliter per gallon and a clear alcohol such as gin or vodka or everclear at the rate of 1/4 ounce per gallon.
During the summer months most growers will fertilize once a week and then cut back to once every two weeks during the cooler parts of the year. Some people stop fertilizing completely from December to March (northern hemisphere), but except for those plants that require a winter resting period, I don't think this is necessary. The plants are still growing and need some nutrients.
In addition to providing fertilizer to the root systems of your plants, be sure to spray them with the fertilizing solution. I usually fill a spray bottle half full of regular fertilizing solution and then fill it with rainwater to use for a foliar spray. Several recent studies done on Phalaenopsis have shown that plants that receive foliar spraying of fertilizer grow much bigger and faster than those that do not receive it. You must, however, be careful to do this early in the mornings and provide enough air circulation to allow the water to dry. Be particularly careful with Phals and Paphs to make sure that you do not get water in their crowns where it can cause crown rot. A light misting is what you want in order to provide good nutrition without problems caused by fungus.