Answer: There are two approaches to this. One is to plant directly in the container making sure there are drainage holes in the bottom and a way to protect the porch floor if necessary. The other is to plant into smaller containers (each with a saucer or double potted to catch runoff) and then group them in the large one. This second approach would avoid the drainage issue and would allow you to change the display at will. This might be useful if it is an area that is viewed during the winter or at holidays. You would also be able to use various seasonal bedding plants as needed to freshen the look.
Watering can be handled in several ways as well. If the containers are very large and the walls are thick enough to provide some insulation from heat, then you may not need to water more than every five days or so. You could also use a potting mix with a waterholding polymer in it to minimize watering. Another possibility is to use a drip irrigation system on a timer.
A low maintenance hardy planting for a shady spot would be hostas and ferns and possibly a topiary of Hedera helix or ivy for extra interest. Annuals such as impatiens or caladiums could be added in the summer for a spot of color. All of these plants would enjoy a similar soil and moisture level.
Good luck with your project!
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