Seedlings are a bad way to get your feet wet in bonsai, IMO. They require different care than established bonsai and can teach you relatively little in how to care for one.

A rule of thumb is that most bonsai are not "grown up" from seeds or seedlings. They are "cut down" from larger established stock.

the best way to get your feet wet with the bonsai "art" is to DO bonsai, not plant seedlings and watch them grow. Bonsai require pruning top growth and roots. That care needs to be learned up front. Seedlings haven't the "heft" or character in trunk that makes bonsai compelling, satisfying and ultimately worthwhile for someone starting out. To develop those two things require unfettered growth of the trunk. In other words, you will have to plant those seedlings outin the ground for a decade or two, allow the trunk to increase in size and cut the plant back to design parameters then. That's a long boring process that doesn't really involve the bonsaiist much. You want hands-on experience with bonsai? Get one and work on it.

Additionally, there are big differences in the material you use for bonsai stock, including whther it can stand being kept indoors (temperate zone plants like the ones you've mentioned won't live very long inside). Red cedar is also a rather poor bonsai subject to begin with for a novice. It requires some specialized pruning as it produces "mature" and 'juvenile' foiliage that has to be treated differently.

The best thing you could do at this point is find a local bonsai club and buy an established bonsai from a knowledgeable dealer (stay away from ebay and remember as with alot of things, you generally get what you pay for) and learn how to keep one alive and thriving.

With any seedlings that you plan to bonsai you should cut the tap root early on. Then splay the horizontal roots out in a large pot. That is what makes the lower trunk expand and will give you a good nebari in the long run. Yes, I know it's a drastic treatment. You will lose some in the process but you don't want the ones that can't take it.

Tony

Thanks for all the great advice. I may pot some of these up anyway, as they're just going to get mowed down if I don't. They may as well live or die via my hand rather than certain death via my husband & the tractor.