My greenhouse is fertilized using a fertilizer system where I pre-mix whatever brand fertilizer 1/4 of the strength recommended on the label. This is fed through the garden hose. I would not use the pre-mixed attachment thing in my greenhouse as the fertilizer would be too strong for the orchids and could cause burns. If you use the jar attachment, you can simply divide the liquid or powder by 4. Be sure to water first to ensure that you are not wasting your fertilizer. Wetting the roots allows them to be ready to take in the fertilizer. And remember to be sure to water with plain water the next time to wash away any remaining salts from the fertilizer.