I started about 25 of these early girls from seed in mid March. They are pretty leggy this year due to the new member of the family being a cat and I had to move the growing lights to the laundry room where there is no sunlight. After I harden these plants can I plant them as deep as the red line I put on the picture or even deeper? I dont know how to post the pic so here is the link
http://home.comcast.net/~printergod2000/tom.jpg
I dont agree with planting deep like many here do. You'll see that the stem below about 3-4 inches just dies and the stem above reroots. Its better to plant sideways about 3-4 " below the surface then the stem will sprout roots all along the stem.
Whether you trench in or bury deep makes no difference as long as you don't shallow plant.
Just snip off the leaf branches that will be buried - or don't - works either way its just easier to plant I think with them trimmed and there is nothing to be gained by having a forked-tongue plant sticking out at the soil line.
Snip them close to the stem or leave a short stub - works either way - I usually leave about a 1/4" stub or so but it's not a big deal either way. It's not brain surgery. ;)