Here's my update on the four little orchids I've conducted my amateur comparison on. They've been side by side, in the same light and temperature the whole time. The two on the right have had nothing but approx. 1/4 strength Miracle Gro regular urea-based fertilizer for over 2 months. The other two have had my regular spray formula, 1/4 strength Orchid Plus by Better-Gro non-urea orchid fert. Both sprayers had 3 drops of Superthrive per gallon.
All have been misted daily with mild fert solution and dunked weekly in rainwater, except when I went on vacation. (and for the week it rained non-stop) I mixed the solutions so that the nitrogen components were approximately the same proportions.
Three of the four plants have healthy new spikes coming on. The fourth is green and healthy but is not putting up a spike yet. It is one of the non-urea fertilized plants. The ones fertilized with Miracle Gro are slightly darker green than the others.
So far, it appears the urea-based fertilizer is working as well if not better than the non-urea orchid formula. Further update in October.
