Why are you confining citrus to barrels? You're not giving each enough room, as any one of them, once it gets growing, could occupy more space than they all have together. That is, IF they grow. Don't know where you are. I'm in Hillsborough county and it's become nearly impossible to grow citrus ... too much disease.

Having vegetable boxes in the lawn and where old shed was (I presume this is over concrete ...?) sounds like a huge mess to clean up after you're done with the space. Would you consider starting with just growing things in the ground, since it already exists and is capable of growing things?

Since we can't see your side yard as a whole, and since we can't know all the things you want to grow, it would be a lot easier if you tried to scratch out a rough sketch of what you were hoping to do, post it, and get feedback on it, or, at least, some suggestions on where to go from there.

Thanks Yardvaark for your comments.

The previous owner loved to plant in barrels or original containers.

I am afraid to kill the trees by taking them out. I was thinking to add more barrels to make a cohesive look.

We are in a process of hiring a contractor to remove the slab concrete & tiles of the old shed. I am open to all suggestions; just love to have a legitimate vegetable garden.

Will send the sketch of the current layout.

They are half-barrels and we don't know if their bottoms have been removed. It could be that they have and they're just forming raised curbs around the soil, and are open to the earth at the bottom. Dig down and explore this from the outside of the barrel. If they do have bottoms intact, I'd suggest lifting out the whole half-barrel, removing the plant and replanting it with better spacing from the neighboring plants. If they don't have bottoms, decide if you want to leave them as is, or dig up two and replant them elsewhere (without the container.) I wouldn't add more barrels unless, as a decorative feature, they appeal to you so much that you just want to have more. They are wood so, of course, are not going to last a long, long time in contact with the soil. I think a long term plan would be better without them.

If you want a vegetable garden, I can see why you might want some concrete removed. I would think it through and commit it to a plan before inviting any contractors to give you a price on removing concrete. Otherwise, it will be harder for them to give you a price and it will likely be higher because they are guessing on a mystery. And you wouldn't be able to compare prices from different contractors because they are each guessing on slightly different mysteries.

To create a plan, draw it out, to scale, on graph paper, This is a small space so it wouldn't be difficult. On the base (starting) plan, draw only simple edges of the permanent elements that will remain. Don't add any shading, patterns or plants ... except tree trunks if any exist. On a copy of that plan, explore changes that you want to make, refining them until they seem like they can't get any better. Share the process here at any point you want feedback and suggestions.