If those main branches are actually trunks, take them out from the root at the ground. If they are actually lower branches, you can cut them off, leaving the branch collar. Cutting off the bottom branches is called 'limbing-up'. By limbing up, you can cause wind damage by not leaving enough weight on the lower part of the tree, allowing the tree to whip around and twist more in the wind. Since you have a shrub right now, and it is sheltered from the wind (at least somewhat) you can start taking the lower limbs off...but only do a few at a time, never more than a third of them. If you want to plant under the tree, do that as gently as possible...the more you damage the Crepe Myrtle roots, the more they send up shoots...depending on the variety of CM you have, you may end up with them all over the place, like I do. :)

I find crapes with three or five trunks are much more pleasant to my eye than a single trunk .

You could cut off one trunk at a time - over a period of time - until you find the look you prefer .

So far, I've cut off only one 'trunk' and only because it was twisted and 'out of sync' with the other four. Although I've not planted anything under it, I noticed today a couple of volunteers. I left them - was that a good move?

Cut one more trunk to have three left and remove all suckers .
You can eliminate the sprouts by rubbing them off .
I was told ( by an Arborist ) that this is a better method than cutting .

Sounds good! Will do that this evening - when it cools down to the mid-90's!
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