It depends on whether you want to make a bonsai about the size this tree is now or do you want to develop it into a larger or even a smaller tree. Either way you need to start removeing some of the needles to let the light into the interior of the tree.
Remove all of the downward facing needles and all of the upward facing needles. Cut them do not pull them out you will destroy buds you may need later is you do that. The ends of your branches should look like bow ties if you view them from straight on like sticking them in your eye. The idea is to encourage an abundance of new buds that will allow you the option of producing branches that are not as thick as the trunk as they are now.
This is one of the problems with some Mugos. Often when they are young they produce branching that is the same size as the trunk and it becomes difficult to produce a tree with decent proportions. It therefore becomes necessary to force the production of branches from dormant or latent buds which will be substantially smaller. This is also the source of knuckle formations when these supper vigorous buds are allowed to develop unhindered. Most bud removal should be done near the middle of July. Remember Mugos are not JBP and seldom push a second flush of growth, though it might happen sporadically it is not predictable or dependable. My most vigorous Mugo pushed out a second flush of growth once in forty some years of bonsai culture with it. However using this method they will produce tons of new buds that will develop into candles next spring.
Vance, the top of the tree has a bunch of candles/branches all coming out at the same place. Should he think about removing all but one or two at some point?
Vance, the top of the tree has a bunch of candles/branches all coming out at the same place. Should he think about removing all but one or two at some point?