I agree completely! That peat-based potting compost is great as long as you keep the plant heavily watered and fed. It's been my observation that once you plant it in regular garden soil, it dries out and it's nearly impossible to re-wet it. When it dries (even a little) it shrinks and allows air to dry out the plant roots...the roots never reach out to expand beyond the confines of the root ball from the pot. I've had some success with knocking (shrubs) or gently washing (perennials) most of the potting soil off before I plant, but you have to be careful not to damage the roots too badly.
When I see local plant sales of locally grown plants, I stock up. I've had the best success with those! These plants are growing in the (relatively) same soil as my garden, and the same climate conditions. Most don't even know they've been moved.
Seeds seem to be the best way, once you get past germination problems. I'll tell you, you can get brain freeze reading germination instructions. *LOL* I bought foxglove seeds and the instructions were so complicated...a period of cold, of warmth, of cold, specific temps, etc. I followed the instructions carefully and nothing. Two packets never germinated. In disgust, I tossed the seeds from remaining third packet onto some dirt beside my clematis and lo and behold....a huge patch of baby foxglove seedlings! I've come to realize nature really doesn't go thru a lot of trouble...just toss the seeds and see what happens.
Annie
