We received a number of emails from folks after the recent spell of
hot weather about blueberries and their leaves turning brown and/or
red.  Now that rain barrels and cisterns are full, take some time and
water them in and your plants should be looking good in no time (this
goes for other fruiting varieties as well)...

I asked Chuck Marsh of Useful Plants, a mentor of ours, and here was
his response.  They should come back with regular watering; you can
prune off at the branch node anything that is egregiously dead
looking:

"Yep, they're not getting enough water.  Blueberries need to be
watered quite a lot (every day at first, then slowly reducing the
watering spacing over time) immediately after planting, particularly
in hot dry weather.  Their roots take a while to get established in
the surrounding soil, allowing them to get moisture from the soil.

Until that happens the container medium can dry out much faster than
the surrounding soil.  Deep watering is essential.  A quick spritz
won't do it.  This is obviously what happened.  See the planting
blueberries text on our website for my watering recommendations.
During hot, sunny weather these recommendations might need to be
extended or even more frequent waterings may be necessary."

Blessings,

Chuck