My wife and I created a garden in a small space at the front of our house. I had to dig out a lot of heavy aggregate left over from the creation of the porch, driveway and sidewalk to make sure whatever she planted would grow. In the pic, you an see that on the left and right are poppies, and in the middle are petite knock out roses.
Now, to the problem. the two poppies on the left, closest to the driveway have died. The rose bush next to it, lost a lot of leaves, but is bouncing back. Before we put in more poppies or other plants, I want to be sure of what happened here and make sure it doesn't happen again.

Here are some facts which may or may not help in diagnosing the problem.
a) The cement is not new, the house was built in late 2018 and we moved in Jan 2019, so I don't think anything coming out of the cement is the issue.
b) This area has had nothing in it, not even dirt. It was only aggregate rock, from when the sidewalk, porch, driveway and foundation were put in.
c) When I took out the aggregate rock, I had to go down almost 20 inches before we got to dirt where these two poppies were put. (I wanted to be sure there would be dirt below all the plants, not rock) The area where the other poppies are did not need as much garden soil, as we only had to dig out about 8 inches of rock before we got to dirt.
d) The entire thing was then filled with a 'Garden Soil' mix for in ground use. We then put down weed screen material and a pine mulch.
e) we didn't get the rain we needed, but my wife watered the plants regularly. As you can see, the poppies on the right, survived, the ones on the left did not. (The pic above is from when the garden was first completed. Since that time, in rapid fashion, the poppies on the left have died completely. No, not 'dormant', died. the ones on the right are still blooming.)
One last fact should it be necessary f) we had the pest company come a week or so after planting and they sprayed all round the outside of the house, as well as sprinkling some sort of granules to get rid of ants. (We'd had ants in the house for the first time this year.) The granules got on the plants, but I used my 'leaf blower' to blow the granules off all the plants later the same day. And I cannot stress this enough, ONLY teh poppies on the left have died.
(More pics of the garden being created are HERE.)

What might be the issue here?

 

The photo of the bed soon after planting, while pretty, doesn't help much to determine why . Do you have photos showing the plants when they are stressed/sick to help determine the cause? What did the roots of the diseased/dying plants look like? Since all of the plants that died are on the same end of the bed I suspect a watering issue.

 

@PilotDane I would agree, but the other plants all got the same water. What I'm wondering (which is why so much detail on the build) is if the depth of the one end caused the water to drain too much thus causing this. My wife has not removed the dead poppies.

 

You have to be careful with areas like yours if the natural soils don't drain well. You can have a large in ground flower pot that has no drain holes. Even though the mulch on the surface may dry water can accumulate in the excavated area especially since the concrete on all four sides is higher than the bedding so water will rarely run off.

 

@PilotDane. What am I missing here? This area was aggregate rock and drained well for 2 years. There was never standing water. In the area where the plants DIED, there is 20 inches of 'garden soil' over dirt at the bottom. Nothing stops the water. In fact, at one point I wondered if that area was drainign too well. . Draining is what this area was designed to do. AND AGAIN, the area where the plants did NOT die had only 8 inches or so of garden soil above the dirt.

 

Only time I ever had any luck with Poppies was when I planted them under a Walnut tree. They loved it and not much grows under a Walnut tree. But I have no clue as to your problem unless the soil you got was bad, but that's pretty rare.