Catonsville Container Conundrum
Is there a list of some kind, of the best plants, preferably perennials, that can be used for container gardening in the Catonsville Maryland area
Just about any perennial will grow well in a container, provided it is hardy to two zones colder than the normal hardiness zone there. Plus it will need the usual cultural requirements for that particular plant-- such as adequate sun, moisture, and nutrients for the spot where you put the container.
Look at a list for perennials that give cultural requirements, find yours, and then narrow it down to perennials that will survive colder temperatures down to two zones colder than your zone (Catonsville is 7a.)
The plants need to be two zones hardier because air temperatures get colder than soil temperatures. In a container the roots are above ground, so to speak, and surrounded by this colder air.