Pro-mix Bk25 is a great one. I use that for many things, one of the best.

I was hopeful that Pro-mix BRK would be a good substitute for mixing my own but it didn't work for me. I tried it in some outdoor containers first. It stayed too wet which is weird since I live in a very dry climate.

Looks like there are several variations on the ProMix with confusingly similar names. BRK20 has a much higher peat content than BRK or BK25, and they use slightly different types of bark between the BK and BRK variants. There is also a BK55 with 55% bark which they advertise "is perfect for growers looking for container stability."

I emailed the company yesterday and got some more info on the different mixes. Didn't really answer which would be the best choice for me, I'll probably try the BK25 first.

"Simply put:
Our BK Mixes are from the Southern US
Our BRK Mixes come from the North (Canada)

A little detail:
We pride ourselves on offering the most consistent product possible so weather you get a northern bark or Southern Bark product our standards and process for preparing the bark is the same. We do not cut corners; the bark is composted until it is Nitrogen Stable (temperature spike and turn... repeat the process until your temperature plateaus. Many other producers throw urea on their bark piles, turn X number of times, and call it good. Truth is weather can shift compost time (temperature and moisture). Once our bark is stable it is then screened to remove the fines and sized. From there we use our other high-quality ingredients to create a Bark Mix that behaves the same year to year in regard to draining and dry down time.

Below is a video from our online training center on BK55 (from the south) created by our Grower Services Department. If you have any more questions I am here to help!
https://www.pthorticulture.com/en/training-center/pro-mix-bk55 "

edit: not sure why that link is broken, tried to fix it. remove the"/%22" that's added to the end of the URL and it works

Well I may be going with the Berger BM7 after all. I just can't find the Pro-Mix BK25 anywhere, shipped or local. BM7 looks like a good mix, same ingredients as the Pro-Mix with 35% pine bark so it should do fine. I'll post an update if I get anything growing in it.

Alright I give up, BM7 ended up backordered half the places I was looking and the few that had it were charging over 3x the cost of the bag just to ship it! Guess bark-based mixes just aren't popular enough to be consistently available, I might end up mixing my own after all...