Answer: Plants growing in containers typically need to be watered more frequently which can leach minerals from the soil. To counteract this, you can feed more often. To keep from over-fertilizing (which can burn the roots and result in excessive foliage growth at the expense of flowering), feed every 2-3 weeks with a half-strength dilution of liquid fertilizer (I use Miracle Gro). Feeding this often will supply a constant source of nutrients to your hydrangea without the concern of burning it. Best wishes with your hydrangeas!
Q&A Library Searching Tips