I heard that it's impossible to kill jimsonweed, but it certainly seems unhappy. It has been the sickliest and most troublesome plant I have. I hope I can give the pertinent information; I'm sorry if I'm too wordy. I started gardening late last year, so I'm a n00b.

Austin, Texas, USDA zone 8b/9a. Narrowish walled paved courtyard. About 4 hours of direct sun, several hours more of light reflected off high light-colored walls. In high summer now, it tends to be 5ish degrees hotter in the afternoon than the airport, as in 108 F when the airport reported 101 F.

I only have containers on a paved courtyard. I planted the jimsonweed in a good-sized pot with standard rich potting soil. I added mulch recently, when it got really hot here.

It overwintered, but barely kept any leaves long enough to get new ones in the spring.

Earlier this year, it got scale and probably spider mites. I sprayed it with a sesame-oil-based bug killer ... but the bottle didn't mention that you shouldn't spray it and expose it to light and heat, so it lost most of its leaves again. But it bounced back and even bloomed three times.

But then the leaves started to look spotty tan and generally run down again, and when I misted it with water I saw lots of webbing, making me think spider mites again. I washed the leaves with the hose and then used the sesame oil again, but this time at dusk, and I covered it with strong shade cloth (50%ish) for three days, and then rinsed it again with water. I've sprayed the leaves with water a couple of more times. It's now in the shadiest corner, but that just means direct sun from 10 AM or so to 1 PM or so.

Now the leaves are looking sicklier, and unlike before, the new sprouting leaves don't look reasonably green. Also, for a few weeks several stems have had slit split bark, so I can see the green (xylem?) and even below.

Now what? Do I just let it sit and hope that it'll get a new set of leaves?

Does it need shade?

I have an battery-powered moisture meter, so I have some control. What sort of watering works? Is it OK with medium or heavy watering (which it got when I was spray-washing the leaves), or should I try to keep it dry, or what?

Surely it doesn't need fertilizer?

Can I ever make it look happy and nice and green?