Vacation Watering Half Barrels
 

I want to grow blueberries in half barrels this season, but will
probably be on vacation a good deal this summer, and won't be around
to water them every couple of days. Any suggestions on how to keep
them moist? I've seen devices for tomato plants, which resemble liter
bottles turned upside down, delivering a slow trickle of water. Would
a few of these per barrel do the trick?