Problems with butterfly bushes (buddleia davidii)
I'm hoping someone might be able to help me with this. Last fall, I planted two small butterfly bushes in my southern exposure backyard in Mesa, Arizona. They were doing great, growing at a fast rate and flowering when spring came. However, as soon as the harsh heat of Arizona arrived early this summer, the flowers started dying, and the plants started wilting. I thought this might have been due to inadequate water (they each had 1 GPH drippers on them), so I bumped the drippers up to 2 GPH. I would leave the drippers on for about an hour and a half to two hours a few times a week. Increasing the dripper output didn't seem to help; in fact, the plants seemed to get worse. I called the nursery I bought the plants from to seek advice, and they told me they thought I was watering too much. So I cut the drippers down to a 0.5 GPH output. They still haven't gotten any better. Are Arizona summers simply too much for these plants? I read that they can take full sun, and they can grow in zones 5-9, so I thought they would be fine.
Should I try to shade the plants somehow? I fertilized them in late spring...don't know if I need to do that again.
Any help would be appreciated. Thanks.