It is a hydrangea macrophylla (a mophead). Acidic soils make the blooms blue. The specific variety is harder to guess since so many varieties have blooms that look alike. One of the best blues comes from a variety called called Nikko Blue. The one in the picture sure looks healthy! I assume the picture was taken on prior years?

I grew up in North Carolina and I remember seeing big bushes of them all the time. I found this picture on google just now. Where should I look to purchase these? The only problem I have is my whole yard is concrete, because I moved to San Diego. I'm not sure whether these will do well in a pot.

They can do well in pots too but pots require more watering, more frequent feeding and storing in the garage during winter. On the other hand, people have less trouble acidifying the potting soil in pots in order to get blues. Nikko Blue can be ordered by mail from many places but I have seen it for sale locally too. Check in May when most nurseries display named varieties (approximate guess) to see if they have NB in stock. One last thing to keep in mind regardless of which variety you choose: some hydrangeas can get wide and so you will need to tweak the pot size to compensate every few years.

Well I was hoping that whenever I buy one that it will be huge! I have three very big wooden barrel-type pots. I use them for tomatoes and I thought they would be perfect for these. Also is ebay a trusted site for ordering bulbs/seeds? I hear of many people using ebay for that. The picture is an example of the ones I have.

Ah, I used to have rain barrels that looked like that. There are some hydrangeas which get rather high and wide so measure the barrel to see how wide it is and compare that to the ones you see for sale. Just remember to acidify the potting mix regularly to get blue blooms. A nice variety that people get when they want blues is Nikko Blue. However, it only blooms once but the blooms last until winter (the colors fade after a while in case you did not know).

If you want the plant to rebloom (and your growing season is long enough where this may be a nice feature), go to the websites for the Endless Summer, Forever And Ever and Let's Dance Series to investigate if you might like one of those in the wine barrel!

http://www.endlesssummerblooms.com/en/consumer

http://foreverandeverplants.com/Index.aspx/GardenFavorites/Hydrangeas

http://www.springmeadownursery.com/plants_results.php?col=commonname&val=Hydrangea