PROBABLY your blueberry plants will come in a similar BARK BASED medium. Secondly, I don't see a reason for disturbing the plants too much, as those are going to be an out doors plants. JMO

BTW: for blueberries you will need to acidify the potting mix, instead of adding lime, methinks.

If the plants arrive dormant (as they probably will), gently removing the original potting mix would be ideal. Nonetheless, it's not essential, especially if the mix looks very similar to what you'll be using (as seysonn mentioned) or if the plants have emerged from dormancy. You might already be aware of everything after this point, but, just in case, I'll add a few more pointers about fertilization/irrigation...

• The pH of 5-1-1 mix without lime is usually in the acceptable range for blueberries, so no further acidification is necessary (and could very well be detrimental).

• If your fertilizer doesn't supply calcium and magnesium, you'll need a supplemental source of both. Since it doesn't affect pH, gypsum works well as a Ca source (premix 1 tbsp per gallon of potting mix). Epsom salt is a good source of Mg -- just dissolve 1/8 to 1/4 tsp in each gallon of irrigation water once a week or so.

• Ideally, you should water your potted blueberries exclusively with rain water. If that's not possible and your irrigation water contains bicarbonates (as most ground water and municipal water does), you'll need to add an acid to your irrigation water to lower the pH to 5.5 or so. The simplest option is white vinegar, but there's a good argument to be made that sulfuric acid is more effective in the long term. If you choose the latter, be sure to read up on how use it safely (if you don't know already, of course).

• Finally, blueberries do best with fertilizers that supply nitrogen in the form of urea or ammonium (as opposed to nitrate). Nitrate forms of nitrogen aren't necessarily toxic (although they can be at high doses), but blueberries don't use them very efficiently (their native acidic soils are naturally low in nitrates).

Thanks! I was planning on using the Foxfarms Acid Loving Fertilizer since it has Magnesium and Calcium in it but when I emailed them and asked about it in regards to blueberries, they told me that I should probably add some more on my own as well since blueberries will want more. Should I still add gypsum and epsom salts if I choose to go with Foxfarm? Or just add a lesser amount? Or do you think I'll be fine with just their fertilizer since it does have those two elements in it?

Also, with the epsom salt, do you have to dissolve it when irrigating or can it be placed around the dripline in the container to be watered in?

Do you guys use a CRF in the potting mix? Osmocote Plus or Dynamite All Purpose?

Dissolve the epsom first.

Maybe cut the gypsum by half? Sprinkling epsom salt on the surface and watering it in should be fine (just don't over apply it). As for a CRF, I did try Osmocote Plus* with one potted blueberry last year, and it flourished. If memory serves me correctly, I top dressed it at approximately 1/2 tablespoon per gallon of mix. The same plant also received weak doses of Jack's Classic Acid Special at every watering.

*Osmocote Plus has been discontinued and is hard to find at this point, so I'll be switching to Dynamite All Purpose Select this year.