hot sun location
My house sits on E-W axis. I have the side/driveway side of my house/plot about 5x15x/hot hot sun and alum siding on house. Too hot for most perennials I've tried. I'm thinking about cactus. will it grow tall in Md? How many could a space that size hold?
Prince George's County Maryland
The Eastern prickly-pear cactus is native to Maryland and grows about 1 foot tall. It spreads, so you can space the plants and they will fill in. See: https://www.marylandbiodiversity.com/viewThumbnails.php?species=1586&showAll=1 It flowers and attracts butterflies.
You also may have success with sedums, which come in many sizes and color from groundcovers to about 1 foot.