I am thinking of putting in a raised garden bed in our back yard here in south-west Florida. The soil here is rocky and sandy, and I've been told by more than one person that some things don't grow so well in this kind of soil. We love fresh blueberries, but that is one of the things that doesn't grow as well or as sweet in this soil as they can up north. Can blueberry plants be grown in a raised garden, and if so, what would the minimum depth of the raised garden need to be?
The main advantage to a raised bed is drainage. If your soil is sandy, it should drain very well without being raised. If you want to build a raised bed for the visual appeal, that would be ok, but having a raised bed isn't necessary and could possibly be a disadvantage if it would make the water table too low for the shallow roots of the blueberry to access. Blueberries like loose soil without standing water where air can reach the roots, but they do need access to water as well (frequent rain/irrigation or high enough water table).
Blueberries actually grow very well in rocky, sandy soils (like mountains would have) and have more trouble growing in heavy, clay soils. It is true that some things won't grow in sandy soil, but blueberries isn't one of them. If the berries aren't sweet as they are up north, I would pay attention to the variety. There are more varieties than I can count and each one tastes different. Some are sweet, some are citrusy, some are gritty, some are so sour that I can't tolerate them.
I've read where magnesium can affect the taste of berries (as well as tomatoes and melons). This could be true in that magnesium is required for chlorophyll, which is what makes the sugars from sunlight. So, fertilizing blueberries with magnesium sulfate (epsom salts) could be a good idea.
Lastly, blueberries love organic matter. They evolved as an understory bush where the leaves from larger trees kept the ground thickly covered with leaves.
Here is a site which talks about blueberries in FL http://www.justfruitsandexotics.com/Blueberries.htm
Here is their facts sheet http://www.justfruitsandexotics.com/JF%20Blueberry.pdf