Do a little bit of everything.
I throw seeds on my hugelbeds and some of them come up. I put seedlings in the hugelbed and they get bigger. I move plants from one hugelbed to another. I pull the weeds out of the hugelbed and
feed them to the chickens. Wherever I pull out weeds, some new seeds go in. Unless it was a big weed and left a big hole; then I find a seedling that will fit. If I pull out a turnip, I can pour some topsoil over the disturbed area that has some seeds mixed in with it.
Unlike conventional agriculture with its regular rows and uniform spacing of seeds in the rows, there is much less planning needed in
hugelkultur. Plants may seem crowded and irregularly spaced, but if you go on a nature walk, that is what you are going to see. I have a celeriac jammed up right next to a salsify in one hugelbed. I was looking at it today and wondering if i
should move the celeriac, but neither one looks worse for the close quarters, so I will let it be. I don't think I have ever seen that combination mentioned in the companion planting guides, so maybe I have a first here. We'll see.
One reason that you will need seedlings is to fill in empty spaces in the hugelbed as the season progresses. I start seeds in plastic pots and when they get to transplant size, I go out with the trowel and look for spots in the hugelbed that look a little bare.