Blueberry Container Gardening
I am ordering blueberries from Raintree Nursery and will be planting in containers. How should I amend the purchased potting soil to have the proper Ph? I will be planting in 1/2 wine barrels? Thank you
King County Washington
Potting soils will vary in their composition and beginning pH, so there is no standard answer for this. One option would be to send a sample to your state's soils lab be tested to determine how much sulfur would need to be added to reduce the pH to a level suitable for blueberries. They may have a special test for potting mixes or soilless media.
If you want to make a rough approximation of beginning pH, you could use the information in Table 21 and/or 22 in this publication: http://extension.uga.edu/publications/detail.html?number=B931
Another option would be to consider planting in aged pine bark rather than a potting soil sold for typical garden plants. In the south, Southern highbush blueberries are sometimes grown this way. Careful attention would need to be paid to watering regularly, since this is a very well-drained substrate.
While your question landed on my desk, I am not in the Pacific NW. You may want to contact your local Extension office, as well: https://extension.wsu.edu/king/