If they're going brown its likely insufficient water - and if you can't keep up with watering in a pot, it'll be even harder to keep it watered in the ground. Move it to a shady area and keep it well supplied with water, plant out in late September. If its been in the same pot for longer than a year or two, make sure its not potbound - turn it out and have a look at the roots, if it is, either pot up into something bigger or chance planting it out, but I'd recommend a bigger pot at this time of year, its not an ideal time to plant permanent shrubs.

I 'd plant it and just make sure you water regularly for a month or so then only if there isn't rain for a week after that.