First, I would caution against digging under established evergreen trees; it is very difficult, as they have tremendous root zones that require very aggressive measures to get through, which is not good for the trees, and ultimately not good for your blueberries, as they will be competing for room to grow as well as nutrients and moisture. If you can plant them elsewhere, start with two-gallon pots. Plant them in the fall when the weather is cooler. If they are happy, they should fruit the next summer (in time they will likely produce more fruit than during their first season). You would have to plant a whole lot of shrubs to eat a few pounds weekly! Space depending, five to seven plants will give a reasonable yield.
First, I would caution against digging under established evergreen trees; it is very difficult, as they have tremendous root zones that require very aggressive measures to get through, which is not good for the trees, and ultimately not good for your blueberries, as they will be competing for room to grow as well as nutrients and moisture. If you can plant them elsewhere, start with two-gallon pots. Plant them in the fall when the weather is cooler. If they are happy, they should fruit the next summer (in time they will likely produce more fruit than during their first season). You would have to plant a whole lot of shrubs to eat a few pounds weekly! Space depending, five to seven plants will give a reasonable yield.