Answer: Usually it is not a good idea to replace organic mulch with rocks unless you have a very specific reason for doing so. The rocks are long lasting but they are heavy to install and also difficult to remove later if you change your mind. The rocks will reflect detrimental excess heat onto your plants in summer and also, surprisingly, in winter. Organic mulches such as larger particles or bark nuggets will last a reasonably long time and have several side benefits such as helping feed the soil over time when it decomposes. Healthy soil is important for healthy plants. So in my experience it is better to use an organic mulch rather than stones.
In your area (based on your zip code you are gardening in USDA winter hardiness zone 7A) the winters are very cold. You will need to bring tropicals indoors each winter to protect them from the cold. For this reason I would suggest growing them as container plants to facilitate the moving process. Some tropicals can be stored dormant in a cool dark place such as an unheated garage, others need to be kept warmer and would benefit from a greenhouse. Your local garden center staff should be able to help you select plants that would be best adapted to your growing situation. Enjoy your new garden!
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