Hi Sprout,
It's true that comfrey isn't the easiest plant to grow in north Texas but I've managed to keep mine alive for several years now and it's actually starting to spread a bit. Fall is a good time to plant comfrey. Yours should do very well under a tree where it will get some shade from our hot sun. If it's a fruit tree, I've heard that fruit trees will benefit from comfrey being grown beneath them. Actually, most plants will benefit growing near comfrey since it has long tap roots that will reach down and draw up nutrients from the soil. My dh has been wanting to plant comfrey under our fruit trees. But he has to wait until the trees are big enough to provide some shade!
Good one Greene! I think I must have missed that article. Off to read...