Plagiotropic growth of Sourwood

I wanted some Sourwood (Oxydendrum arboreum) trees. I remembered the beautiful fall leaves from when I lived and hiked in the east. I was so happy to find Sourwood on various lists of recommended trees for the Seattle area, such as Great Plant Picks from a local arboretum, but I never saw them in anyone's yard. I would be the first!
Most nurseries did not have any Sourwood, and workers looked confused when I asked. Finally I found some saplings for sale. The knowledgeable nursery worker said the owner had grown them from cuttings, but because he had used side branches the new trees were tending to have sideways growth, and were not developing a central leader. He thought eventually the trees would revert to a more normal growth form. That has not happened. Each year I stake and prune a bit, to help the trees along, without any real success. By the end of the summer the new "leader" is going sideways again, and the trunk has strange kinks from all these direction changes.
Is there any hope? I have been reading about this in my Propagation textbook. This sideways (plagiotropic) growth from lateral branch cuttings is apparently noticed in some plants like yew, Norfolk Island Pine and Podocarpus. It is sometimes done on purpose to produce a weeping plant.
This effect of source plant propagule position on the growth of the progeny is called topophysis. Upright growth of progeny after using upright growth of source plant for cutting is called orthotropic growth.
Anybody know the answer to this one? I am thinking I should cut my losses and rip the poor things out and plant a vine maple. I don't want a weeping Sourwood (but it would be a first!).

MLM, I really like the quirky growth, it adds a lot of interest. Trying to establish a central leader is a challenge but you should be good if you stake the next largest/most upright branch as close to upright as the tree will take and cut back all the branches that are competing with the new leader.

Have you seen this video? It explains the process pretty well:
http://www.youtube.com/watch?v=lHnv0AstLK4

Update on my Sourwood trees. I had decided to grow them as "weeping" cultivars, and embrace the sideways growth, at least until the trees I started from seed last year get bigger. I figured I would stump any plant experts who came here with my weird shrubs 9not that any do come here). Now check out the two new branches on one of the trees, with strong upward growth. They have somehow been "released" from plagiotropism. They remind me of water sprouts on an apple tree. They seem much more vigorous than the other branches.
What do you think? should I choose one as a new leader, or are they too far from the trunk? Or should I prune them out?

Pistil, in your first image, prune crossing branches and inward growing branches (best before spring growth begins). Proper timing though is not always feasible or controllable, it's easier and more likely to get as close to proper times for each species as possible. Especially if you're a fair weather gardener like me (do as I say, don't do as I do,lol)

The new upright growth is referred to as water sprouts as you mentioned, I would remove them as they usually just take nutrients from the rest of the tree. They would compete with a main leader but never be as strong as central growth from the base of the trunk. If I were you, I'd stay the course of embracing a weeping form.

Here's some information I've found, this is usually a very informative site:
http://homeguides.sfgate.com/sourwood-tree-care-26085.html
Pruning

Prune sourwood in early spring before its new growth starts. Shape the young tree to establish a single, strong trunk with five to eight evenly spaced branches beginning 5 feet from the ground. Prune an older tree to maintain its shape and remove pest-damaged, broken, rubbing or downward-growing limbs.