Yes, but watch the amounts. Use 1/2 dose for seedlings.I have had very good success with Miracle-Gro's Nursery Select (20-20-20) vs. regular Miracle Gro ( 24-8-16 ).You can also use the Quick Start plant food on new seedling.For Hydrangeas, I have used aluminum sulfate sucessfully which is what the Sunset Western Garden book recommends. I used about 1/3 cup around plants that were 5" tall and they turned nicely green in about a week.
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