Orchid fertilizer? Orchid food? Is there a difference or are they the same thing? Orchid plants make their own food using carbon dioxide, water and sunlight, so orchid food/fertilizer actually refers to orchid nutrients. Like most other plants, orchids need the macro elements (nitrogen, phosphorus and potassium) and a range of micro elements, such as calcium and zinc. There are many orchid fertilizer recipes, so which ones do you use and when? With orchids, you really are wanting flower blooms for as long as possible. Giving high nitrogen concentrations to your orchid plant will only encourage foliage growth and not flowering. High nitrogen is fine when the new shoots are emerging but the other two macro elements are more important for flowering. Potassium is the element that is responsible for flower development and phosphorus for flower production. Commercial orchid fertilizers list the N:P:K ratio as numbers, for example 30-10-10 has three times the nitrogen concentration as potassium and phosphorus. Because these ratio numbers are merely percentages, the gardener needs to work out the actual concentration of nutrients that the plant requires. For example, 150 to 200 parts per million (PPM) of nitrogen (N) is fine for periodic feeding of orchids.
Most orchids are grown in soil-less potting mixes and so micronutrients need to be fed to the plant. It is very important that you check the orchid fertilizer label to see if they have these listed. Micro elements are needed by the orchid plant for new growth and support for the flowers. The orchid fertilizer formula that you use needs to match your potting mix. Orchids that are grown in bark medium will require more nitrogen as bacteria present in the bark utilize nitrogen for themselves. If you are wanting to use organic fertilizers, that is fine but you’ll need to use larger quantities as they contain relatively low nutrient concentrations. Slow-release fertilizers are not that effective in orchid potting mixes as the granules tend to be washed out through the medium before the nutrients are released. Water-soluble orchid fertilizers work well. A rule of thumb here is to “fertilize weekly, weakly”. When in doubt, too little is better than too much.