Answer: Plants are amazing, aren't they? When you say "dish garden" I picture a fairly small, perhaps shallow, container. This wouldn't allow much room for root development to support larger plants. Also, you didn't mention if you fertilized the dish garden. Plants will very quickly use up soil nutrients in a container, so they need to be fertilized regularly, perhaps every two weeks. The plastic, gravel, and poor soil sound very challenging too, but once they were able to get through the plastic, perhaps in a small tear or hole, their roots were free to spread and obtain nutrients. However, eventually they would use up the nutrients in a small area, so that soil would need to be replenished as well. The plastic may have helped to keep the soil moist, like a layer of mulch.
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