You have to train B. alternifolia to a single trunk else it will form a huge mass just like like that, and plod upward in an ever-larger green mound. Training to single trunk (standard) involves staking and pruning and choosing when to do so, as it blooms on last year's wood and you'll lose the flowers when you start hacking. Sometimes staking is not necessary, but I suspect that plant needs it.

Dan

Looks like it might have been hard pruned already, which could be part of the problem. Otherwise, you just have to wait for it to mound up on its own. But not in that space, unless you make the bed bigger.

I would go with Dan's suggestion.

Take the strongest, thickest, straightest branch and stake it up vertically. This will become the trunk of your weeping butterfly bush tree. Then prune back all of the other branches.

I know this sounds severe, but what you're doing is making a mini-weeping tree or what they call a standard. It'll eventually look like a shorter version of a weeping cherry.

You'll want to decide what height you want that one branch (trunk) to weep from and then just cut it at that height. It will sprout from there and those sprouts will form the weeping branches that will flower next year.

Keep in mind that for a few years, the main trunk will try to sprout along its length. You'll want to maintain the trunk by pruning these lower branches so that the shrub can focus all of its energy on developing the branches at the very top.

It'll also take a lot of energy and some time for the trunk to thicken.

Mine was doing great until the weight of the winter snow cracked the main branch (trunk). What a bummer. I should have done a better job of supporting the main branch on the stake.

Best of luck to you!

Update, now that I realize the picture in the plant catalogue was a trick,,,,and I have done some pruning ( tho I hate really chopping off healthy branches) here is a recent pic of my weeping budelia. For some reason it did not like the cool wet spring however and I did not get nearly half as many blooms as last year. It has sent out underground suckers and I had 2 new ones that I could train from the start

Here is a link that might be useful: budelia