Answer: Hibiscus is not winter hardy in your region which is why you need to keep replacing your plant. It's normal for some of the older leaves to turn yellow. Simply pull them off so your plant looks more attractive. If even the new growth is turning yellow, it could indicate over-watering or a need for fertilizer. Feed your hibiscus with a water soluable fertilizer (such as Peter's or Miracle-Gro), spraying the foliage as well as pouring it in the ground around the roots of your plant. This should help your plant green up.
Hosta leaves can turn yellow if the plants are over-watered or the soil doesn't drain well. Try watering deeply but infrequently during the summer months to help avoid crown or root rot.
Best wishes with your garden!
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