Carol, knowing what breed of dog you have might help elicit the most appropriate suggestions. I don't believe you said you didn't walk your dog. It's perfectly normal for people to want to have their dog outside with them without being able to run away into danger, and to be able to 'use the facilities' without a person having to go outside with them. Barrels do not taper toward the bottom, so would provide solid fence sections with no gap at the bottom like the shape of a traditional flower pot. There are individual pots that do not taper, and rectangular planters that could be purchased, or you might enjoy making some, IDK. I would probably use evergreen shrubs, like Gardenia, Osmanthus, Azalea, Rosemary, with other plants tucked between. Knowing how much light this area should get, and what time of day, and your garden zone, would help with more specific suggestions. You can find your zone by typing your ZIP code in the box on this page. Stored in your profile (link to edit here) it will show up next to your name automatically when you post.

For that large of containers, it will be cheaper to make your own unless you have access to wholesale sources. There are scores of different potting soil recipes - seems like everyone has their favorite - but all good ones have in common very good aeration and drainage. That's why garden or topsoil and compost are not recommended. A very common mix is 1 part peat (or coir), 1 part bark fines, 1/2 part perlite, pumice or Turface (high fired clay) and 1/2 part coarse (builder's) sand. For each 1/4 cubic yard, you will need to add 3/4# dolomite lime and some sort of slow release fertilizer, like Osmocote (according to directions). For short term or seasonal plantings you could add some compost or composted manures, but for long term plantings this is not recommended. As it continues to decompose, compost or any other highly active organic material will break down and compact and you will lose aeration and begin to experience drainage problems. And for long term container plantings, I'd avoid using anything but the potting soil in the containers. Any other material not incorporated into the soil mix will create interface problems, ultimately impacting drainage, and adding any significant quantity of styrofoam or other material will alter watering requirements. Plus, several of the plants you plan to include will appreciate the full root run of all the soil available.

What zone. What is the surrounding garden like?

@Jennifer-- I hear ya! We have another rowhouse that we rented out and I did a big wooden planter box in the front. Loved it so much I did smaller versions on the upstairs windows. They are never filled because its such a pain for the tenants to water the plants out the window. I might have to get some fab fakes to fill them in. But our current home's curb appeal would be greatly improved by some kind of planter box.