Seems as if the leaves are browning from the edges inwards so it is possible that it may need more soil moisture. Some greenhouse hydrangeas are mopheads that suffer from transplant shock and their leaves can initially suffer from multiple conditions when you first plant them. But for starters, check the soil moisture.

When I increased the size of the picture to get a close -up, the soil (or what's visible SE of the plant) seemed to be dry.

Sugestion: I would use a different type of mulch where the chuncks of material are cut smaller. For example, shredded pine bark mulch and hardwood mulch are cut smaller/finer. Your mulch pieces are so large/few that they may not protect enough and allow soil moisture to escape.

Water the soil from the crown outwards early in the morning since the roots have not had time to grow outwards from the area covered by the pot/container. Then keep 3-4" of mulch up to the drip line.

Do not water the leaves as this can promote powdery mildew infestations on new greenhouse leaves (or other fungus).

Water the soil (1/2 to 1 gallon) when you insert a finger to a depth of 4" and the soil feels dry or almost dry. It is best to water deeply than often and little (not deeply).

By the way, too much sun would make the leaves in direct contact with the sun turn all yellowish or whiteish -including the leaf veins- while the other leaves remained dark green.

A summer warning: as summer approaches, the leaves in non-established hydrangeas may wilt and droop during the worst of the summer months. As long as the soil remains moist, they will recover overnight. Afternoon shade, 3-4" of mulch and frequent checking of the soil/leaves are the solutions. The plants may do better on years 2-3.

Luis

This post was edited by luis_pr on Sun, Jun 1, 14 at 3:15

THANK YOU so much for taking the time to help. I have been watering, but I think I need to do more of a slow trickle for a longer time and try to keep it away from the leaves and get the base more.
I really appreciate all your suggestions.

How many hours of sun does that get? A tiny one fresh from the greenhouse shouldn't get more than a few hours *max*. If more than 2-3 hours direct sunlight, move to a more shaded area or into the shade of a larger plant/tree, etc.