Fertilizer Injector Dosage


In setting up my fertilizer injector over the weekend, I had trouble understanding the table of dilutions for making the stock solution. The tables are based on ppm (parts per million). Can you tell me what range of ppm for nitrogen is appropriate for the "weakly weekly" fertilizing of orchids? I have also noticed small, shiny black spheres on some of my plants. Do you have any idea what these might be? — Sandy Denman


According to Thomas Sheehan, PhD, the recommended range for most floral crops is around 200 ppm of nitrogen. I would say that 100 to 150 ppm would qualify as the minimum dose for the more frequent feeding. The small, black spheres to which you refer are the spores of the wood rot fungus that is always present in bark-based composts. They are not harmful, just unsightly. — Ned Nash