I would keep it simple.
Keep the pipes mounted external and build some covers to make it look nice.
Dont even start destroying your masonry. It will make you $ad.
Plaster might work. You could also get an air hammer and chisel out a channel. That would likely look best. However I’d be worried about getting to the pipes if something busted.
Another option might be to make a small wood box to fit over the ledge with an overhang to fasten the pipes too. Good luck
A search of YouTube for “Masonry/Concrete Question, How Conceal Tubes Against Wall” found:
https://www.youtube.com/watch?v=CtIjqrPGJZY
Better off leaving the pipe as is and just paint same color as wall. No material you put there in an attempt to trowel over the pipes will stick well.
The pipes only “stick out” to you. Almost all stuff like that sort of fades into the background, so to say. Pay real close attention the next time you walk down the street and deliberately seek out wires, pipes, etc. You might be surprised how much you never noticed or thought about before.
E.g. Are you inclined to cover up that downspout visible on the right?
Run your distribution tubes along the ground. Water your plants with the thin risers you show. Don’t mess with the concrete.
Stucco is difficult, at best to try to match if it's aged at all. So any work you do will stand out as a patch, unless you re-paint the entire face of the wall you cut into.
If that pot is the only thing you water from that pipe (can't tell if the pipe supply comes up from the ground to the "T" or from the right) they make tan piping for the line you want to run to the pot, so it won't stand out as much, and could be re-done smaller all the way arouund. 50' 1/4" Tan Water Hose - shorter lengths are available, just got this first click.
Use white duct tape.....................
I think embedding them in the wall is a bad idea - especially if there is possibility of freezing.
Maybe upgrade the piping so that it looks like, or is, hanging rod? Then mount it to sturdy stand-off brackets, which you can hang pots or decoration from? Or vines?
Hiding your Claymores in the bushes is even harder!
I would make a wooden box. Attach L metal bracket to the box were it will set against the wall (the back out side of the box). Them drill holes in the concert shelf were the bracket will fit. Secure it will screws (both box and concert. Secure the L Bracket to the box first, then to the concert.This would allow a small space between the box and the wall. Allowing water to run off the box if you make the box with a slopping lid. Make the box with hinges for a flip open lid. Have the lid to open away from the wall. So that the piping to the plants appear against the wall, and not over the top of the lid. Lay the piping inside the box. Now make a notch in the side of the box were the tubing will run to the plant. Close the lid. You can paint the box to match the wall or the shelf. Also with the box having an op enable lid you can arrange the plant piping wherever you need it. The box can be painted and maintained as needed in the future. If you no longer need the box. just unscrew it and disconnect the piping were it was fasten originally. Discard the box with all the inter piping in place . This setup will allow you to move the box to a different location if desired.
My suggestion is to run a small diameter plastic pipe above and parallel to the ledge, at the same height as the top edge of the big pot.
Get window box style planters to flank the big pot on either side. The pipe above them becomes a manifold from which to water each of the three pots individually.
Plant one or more cutesy flowering vining plants in the boxes, and train them up and along the pipe. Additional smaller plants can go in the boxes, too, giving you a tiered effect.
Pipe now hidden.
No drilling the big custom-install pot, the wall, or any part of your home’s exterior.
No messing with the stucco, very important.
Maximize flower and foliage display.
Good artsy-fartsy effect with view from street. No ugly little clay pots.
Each pot’s water can be customized from its own downtube.
Plant some vines to cover them.
https://www.youtube.com/watch?v=aSLJCPR1Prw
Cast your own aircrete blocks with the overhang. Add dye to make it decorative. Easy peasy.
Just start with the pipe clamps like on the corner- but make sure everything lines up very straight. You might be surprised that it looks OK just like that.
it almost looks like a decorative accent right now.
Just secure it very neat and straight and sturdy and paint the pipe clamps dark brown.