Agree with nickyn. I guess you would need extra room for the trench method so’s not to disturb original root planting.

Trench’em! :-)

I’m in Seattle. If you bury your roots down deep they are more likely to be cold and the plant less happy. With a trench, you can mulch over the area with dark stuff and get nice warmth on the roots. The roots will spread downward to get moisture, but the bulk of them will be up top absorbing that nice heat that is so scarce here. Yes, the trench takes a little more room than burying straight down, but your plant is going to get that big anyway, so it will need the space eventually when it grows up.

Deep containers, especially if black, also make for warm roots.

Erik, when I potted up, I only filled the pots half-way, so that I could add soil mix to the pots as the stems grew upward. I’ll keep adding until the dirt is up to the rim and the seedlings have a thick stem. I won’t let them get flowers on them. Then I’ll plant them out in raised beds that the soil is 6" deep. The roots should be dense enough so that the plant won’t be spending all that time forming more roots. It’ll just have to acclimate and get growing height and flowers, I hope.
A cloche over the soil before planting out would be good, too. Mine is already almost 60º. The tomatoes would be happy with that!

Jane, on chilly Whidbey Island

I guess if you want to cover all the bases, did a Tomato planting hole at a 45 degree angle!