Answer: In general, your box should be as big as possible (especially important for outdoor plants as it helps the soil stay moist longer) and lightweight but strong. In my experience it is rather difficult to construct a wooden box that is portable -- the combined weight of the box and the soil and the water and the plants adds up very quickly. If you make a box out of wood it can also be expensive; you might want to use screws and blocks, or brackets on the corners and use a naturally water and rot resistant wood such as cedar or redwood. Having said that, you might want to look into alternative containers such as a half barrel or large galvanized tub from the lumber yard/home center or possibly the large plastic household "tubs" or storage boxes sold in general merchandise stores. You could set these on casters or a dolly of some sort for portability. Next, you will need to consider drainage -- the container needs to have holes in the bottom so excess water can drain out. Whether you keep it indoors or outdoors, be sure to select the plants accoring to the amount of light you have. You will also want to use a good potting mix. Good luck with your project!
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