Answer: Plants in containers can be adversely affected if too much fertilizer is applied. Rather than risk burning your containerized plants, why not feed them diluted fertilizer more frequently? I'd recommend using a liquid fertilizer such as Miracle Gro, Peter's or Shultz's, diluting it to half-strength and feeding every 2-3 weeks during the growing season. I use one tablespoon of the fertilizer diluted in one gallon of water and water my containerized plants. Feeding this way will assure a constant source of nutrients without the fear of overdoing it.
Best wishes with your roses!
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