Would building up the soil (raised bed) help?

Do you have limited soil near the wall?

"Do you have limited soil near the wall?"

I'm also trying to picture what this looks like, so I think the answers will be of limited utility unless you show some pics of where the action is at. Sounds like a case of engineering from what you've said though, and just to increase the water flow. If you have dripline with integrated emitters every so many inches, is it long enough to loop around each plant possibly instead of just running it in a straight line? Other random thoughts would be to bury a plastic liner along the face of the concrete so it doesn't wick away all the water; and that a natural mulch barrier sounds pretty important, but with the heat thing, I probably wouldn't put plastic film on the surface instead of real mulch. Those three would be my preferred way to tweak it, and so you don't lose the season thinking all is hunky dory you could buy one of those two prong green 3 in 1 moisture meters off Amazon, eBay or Walmart for like $5. They can go in the ground around 10 inches and are pretty useless but probably are close enough for government work lol
PC

< dripline, 2 gallon/hr for ten minutes twice a day cuz I have pots as well. So options are:>

Not nearly long enough period of time for a drip line for inground plants and it is too frequent and so shallow watering not deep watering.

When you run for this brief time on the containers plants is the water running out the bottom of the containers? What size are the ontainers? Can you separate the line so the inground plants are on a separate line? If not can you just change the drippers on the containers to 1 gph or even 1/2 gph drippers so that you can run the line longer and less often.

Try to get the inground plants on 1-2 gallon at a time (1.5 hour run with 1 gph drippers, 45 mins with 2 gph drippers) every 5 days and the containers if good size on 1 gallon per day all at 1 time or at least 1/2 gallon 2x per day. But if the containers are too small for the plants then you may have to do them more often.

And if you slip a 1" sheet of insulboard or even plywood between the wall and the plants it would help. Anything to cut down on the heat the wall absorbs.

Dave

In my imagination, a drip system cannot moisten uniformly. Most of the water will go downward by gravity.
In hot days, the soil next to the retaining wall also can dry up quickly. This can be a bigger problem with concrete material under sun for long hours..

We are experiencing some heat wave. And I have found out that I have to increase the amount of water per plant by about 50%.

Sey

Thank you all for your responses.

Wall is about 2 feet high. Distance from wall to fence is also about 2 feet.

1) The plants in retaining wall have 2 2gph emitters and pots have 3 1/2gph emitters. yes, the water runs out of the pots.

2) I tried hooking up another dripline, using the wall spiget. The timer sucks and pressure make the hose leak.

3) 6 years ago I had 9 feet tall tomatoes. Now they barely grow due to drying out. It doesn't help some of the neighbor's roots are growing in my yard. I tried to dig them out during spring.

Currently, there's two emitters but I am going to try three emitters and mulch heavily. I will also water deep manually once or twice a week.

Hope your season is going well Dave.