Lack of moisture could be a cause for all the browning if leaf browning is occuring everywhere. Maintaining the soil moist -not wet; not dry- should be the goal. Mulch can help and so can using the finger method.

Overwatering could also be a cause. If the roots remain wet for too long, oakleafs are notorious for getting root rot. The symptoms would mimic the ones of lack of water because rotted roots cannot absorb water well and the growth above ground browns out. Once root rot has taken a hold, there is not much that one can do. Watering only when the soil feels almost dry or dry helps. Use of mulch (3-4") helps. Planting above ground in raised beds helps if you have clay soil (clay soil drains poorly).

Winter damage can also be a cause browning during the summer time but I doubt you would see this issue in Zone 9 to this degree and I would expect it to be limited to some stems, not thru all the plant. Oakleafs are cold hardy to Zone 5.

In addition to moisture problems, the hydrangea leaf curler can cause leaf curling; fungal infections such as powdery mildew can cause curling as well.

Luis

Hi - I lost my 3y/o Pee Wee Oakleaf after surviving a center-cane split from the 36" snow-pile ... mended, healed & gave me more than a doz cluster blossoms!!! Alas came nightly storms followed by steamy days in Jul ... planted at the bottom of a slope -AM sun site ... it was wet feet, as Luis posted.

Left him there for a while hoping for revival ... by end of Aug I replaced him w/ a potted Nikko-cane I succeeded to root & flowered ... should be happy in that site!!! Fingers XX'd!!!

Good luck ... (BTW - which Oakleaf do you have?)