|I had 2 Diabolo's planted in mid August, 6 weeks ago. We then had a very severe heat wave for several weeks (very high 90's), but I watered daily the first week, then every other day, and mulched right away. Even so, from the very first days, the leaves started burning up...edges turning crispy and brown. That is still happening, even now that weather is cooler (mid 80's). However, there is continuous new growth at the ends, while the lower leaves burn, or turn yellow. This is causing an unattractive look - bare from the bottom for 3 feet, then some leaves for about 1 foot. They are in very good light, but not the brightest.|
|Transplant shock is always a serious possibility when plants are set out in the heat of summer, especially so during a drought.
However, foliage loss at the base of a plant and browning edges are sometimes caused by overwatering. Your goal in watering is just to keep the soil evenly moist but not saturated or sopping wet. You would water as needed to supplement natural rain, and the way to tell if and when you need to water is to dig down into the soil with your finger. You need to check the potting mix and the surrounding soil because they can dry at different rates. An occasional deeper watering is preferred because it encourages deeper roots as opposed to a daily light sprinkling. To judge how effective your watering is, water and then wait a few hours or overnight, then dig down and see. It can be surprising.
Using several inches of organic mulch can help keep the soil more evenly moist for longer periods. You will find that rain, cooler weather, and less sunlight all help reduce watering needs. Since your plants are not in full sun all day long (more sun would be their preferred location) they will need somewhat less water than plants in a sunnier location would.
At this point, careful watering and patience are the best things you can do. Next spring, the plants should leaf out normally. Routine pruning would include removing any winter damaged branches. They may also be trimmed back as hard as needed (even as low as to the ground) to encourage branching and denser growth from the base. Pruning would best be done in the early spring, if it is needed. Good luck with your ninebarks!