Disney world does this! Lowes sells the 4 to 6" round PVC pipe with holes already drilled. Purchase an end cap, fill with rock, soil, and plant. I will often put these in the center of a very large pot to stabilize, and add amazing height and color to a container that has trailing plants (no end cap or rock needed if you are placing in a container)
Great collection here of hardy lantanas: "Lantana has long been sold as a staple of the annual flower bed and now more interest is being paid to the development of winter-hardy lantanas...from Zone 7b south. We are offering several perennial lantana selections which, in tests around the country stand up to the industry standard, Lantana 'Miss Huff', while offering an array of new colors."
Penta are one of the very best annual flowers for attracting a butterflies and hummingbirds to your beds and containers. Ours have excellent hybrid vigor with clusters of tubular flowers covering the plants all summer. Penta are sun lovers that shrug off summer heat and grow well in both northern and southern climates. 5" deep Premium pot.