Luis,
Thanks for your sharing. You're on point! I do have sandy soil, so it's necessary to fertilize my plants. And due to my injuries and laziness, slow release fertilizer is always my first choice. In spring it's not a problem to have rains because I live in Seattle area. However, we have a very dry summer (from late spring to early fall) and I'm afraid that the fertilizer granules won't get wet throughout the summer if I don't mix them into the soil. That's why I'm considering water soluble fertilizer even though it needs a higher frequency.
Next year I'll do as you suggest and see how my roses do. I think it's a good chance to learn about looking for a harmony balance between I and my roses.
