I bought 4 potted pine Christmas trees 3 years ago, topped them severely, and they are thriving in my homemade soil mix (even thru the Texas summers). But they still look like pompoms on a stick. Is is safe to hard prune most of the bushy branches to give them a real Tree shape? I have let the lower branches grow really long, but they are so thick you can't see the trunk at all.
Thank you for any advice.
~Marcia Cash, Traveler in Thyme

Maybe you should post a picture, so we know what we are talking about. For starters.. on the one hand you talk about pine, but also call it a christmas tree, which typically are firs. And the treatment is not similar..

here is the tidiest of the 4 whatever-they-are Christmas trees, in a 10" bowl.
I thought they were pines because they have survived 3 Texas summers, and I didn't think fir trees were able to do that!
But what do I know <LOL> the only evergreens we have around here are live oaks and ashe junipers.
Thank you for your help.

I think I would be reucing the foligae considerably. It is difficult to say what, you need to decide that for yourself, but it is very dense. It is the kind of material that I would plant in the ground for 3 or 4 years to get some girth on the trunk which looks quite thin.

I do plan on over-potting for a decade or so, until they get bigger. I just wonder if reducing the foliage retards trunk size, or helps it?

Reducing the foliage will not in itself effect the trunk size. What I should have said is that I would thin the foliage but not touch the leader, that I would allow to grow unchecked.
I would remove some of the excess branches unless the style was to be broom, but that would not suit the species.

by "the leader" you mean the top center? I already whacked the tree back severely, since the growth was so vertical. I thought letting the lowest branc grow long helped the trunk get thicker? Trying to be patient here......I'm an artist, this is like Slow Sculpture <LOL>

The leader is what will thicken the trunk if left to extend. The lower branches have no effect on the trunk. If allowed to grow long any branch will thicken at the base.

The leader is what will thicken the trunk if left to extend. The lower branches have no effect on the trunk. If allowed to grow long any branch will thicken at the base.

this is not totally true...leaving the top to grow will thicken the whole trunk,while letting a lower branch grow uncontrolled will thicken the trunk below the branch only. this is how taper is formed in slender "taperless" trunks

It will also thicken the branch which is what I meant.