Terminal buds and leaves turning brown and leaves wilting is symptomatic of Botryosphaeria Dieback, Phomopsis Dieback, Phytophthora Dieback, or Rhizoctonia Root Rot dieback. All four diseases spread rapidly and may threaten an entire plant. They are more active in warm summer conditions. It can also be borer damage. 1) Phytophthora cactorum causes the central vein of a leaf to turn brown and the discoloration extends to the petiole on tender new growth. The infections spreads outward from the midrib tissue and the leaf wilts. Infections are more severe on azaleas. Some varieties of rhododendrons are vulnerable (Chionoides, Catawbiense Album, Nova Zembla) and some are resistant (Roseum Elegans, Scintillation, PJM). Control of the disease is difficult. Since the infection goes from the roots to the tips, when you see the symptoms it is too late. To prevent it, use a raised bed with lots of sphagnum peat moss. Prevention with fungicides and careful control of exposure to high humidity may be practical. 2) Botryosphaeria dothidea causes leaves to turn dull green and then brown and roll and droop. Cankers form on branches which may girdle the branch. This is the most common disease of rhododendron in the landscape. A typical symptom of this fungal disease is scattered dying branches on an otherwise healthy plant. Leaves on infected stems turn brown, then droop and roll inward. These leaves often lay flat against the stem and will remain attached. The pathogen can infect all ages of stem tissue through wounds, pruning cuts, and leaf scars. Heat, drought stress, and winter injury can increase disease incidence. Cankers on branches can gradually grow through the wood until the stem becomes girdled. Diseased wood is reddish brown in appearance. Discolored wood viewed in longitudinal cross section often forms a wedge that points toward the center of the stem, and the pith may be darker brown than the surrounding wood. Sanitation and applying a fungicide such as metalaxyl (Subdue) after pruning my provide some control. Plants should be grown in partial shade, with mulch and kept well watered during dry periods. All dying branches should be promptly pruned out in dry weather and all discolored wood should be removed. Plants should also be protected from rough treatment during maintenance activities to prevent unnecessary wounds. 3) Phomopsis rhododendri symptoms vary from leaf spots to chlorosis and then browning of leaves which then wilt. Browning streaks extend down the stem to a wound. Fungicides such as metalaxyl (Subdue) should control an outbreak. Sanitation and applying a fungicide after pruning may provide control. 4) Rhizoctonia solani: causes small necrotic spots on leaves, which later become dark brown or black. Defoliation follows severe leaf spotting. The fungus is omnipresent in the soil and appears to be most virulent at high humidity levels. Microscopic examination of roots and crown are the surest diagnosis. Cultural practices to control this disease include improvement of drainage and avoidance of excess irrigation. [Return to Problem Menu] 5) Ends of branches die when a Rhododendron Stem Borer, Oberea myops, Dogwood Twig Borer, Oberea tripunctator, or Rhododendron Borer, Synanthedon rhododendri, is in a branch. Borers only affect the portion of the plant away from the roots from the borer. If the borer is in the main trunk, then the entire plant will wilt and die. The plant can be save by cutting off the area with the borer and letting the plant regenerate from the roots. There are no conventional insecticides that will kill stem borer larvae once they are inside the branches. The best control option for homeowners with only a few plants is to prune out and destroy wilting branches in early spring or late summer. Here is a link that might be useful: Common Problems and Their Solutions.

The detail image with the dried leaves look just that, dried out. If you dry mint after harvesting it looks very similar. Your plants are baking and drying out. The suggestion about creating shade for them was good. I'm sure there are large plants with lots of foliage that do well in your zone with regards to sun and heat. I can't tell you what they are - I deal with cold issues here not heat! But if you look on neighbors' decks, patios, front steps, etc. you'll see them. Do a little research on them...make sure none that you choose are toxic. It's never good to put plants you want to ingest next to ones that are poisonous. But get a number of them and create some shade for the plants you want to grow that hail from cooler zones. It can look nice and hopefully provide that cooler patch of shade and green for you. FataMorgana

some of my leaves AND my stems turned brown. That at least was obvious to me. Out they went. But just the leaves, I guess one has to wait and see. (is it or isn't it, to be or not to be?)

Thanks for the reply cozy.I took a branch to a local garden center and had a couple of experts look at it,they confirmed my suspicion that it was to much water.Later that day I dug them up,the soil was wet to the touch and cool just a few inches down.I now think it was a combination of to much water and to much mulch early in the season,tomatoes don't like to stay wet or be in cool soil. The picture I posted was pretty true as far as color,the stems were very dark.I don't think it's to much nitrogen,other plants in soil preped exactly the same way are doing well.The tip off for the garden center people was the fact that the leaves were browning from the tips and the fact that the stem when broken open was very wet,dripping wet actually,the inside of the stem also didn't have brown streaks ruling out most bacterial problems.