interesting to read this thread - i have been getting a lot of liners in the last year or two and really do not do anything special - most are put into containers and "planted" out of sight until ready to go out in public
last fall i went with miracle grow soil and the 25 or so i ordered did ok was hoping for more growth, although some did very well - i have since asked my local nursery to special order metro mix 510 which i good friend told me is great and is used by nursery growers - this was confirmed when the nursery person said she used it when she worker for a grower - we shall see how they have grown since last year
have not paid too much attention about how deep i am planting them - no stem rot here to date.