I had the same happen to both of my weeping cherries this
summer. At that time I cut the straight branch approx. one-
half inch from start of branch or intersecting point. But
in fall zone 5 I would wait untill spring to prune.

If you know a little about grafting you would know that the trunk is a vertical rootstock which gives your weeping plant height before it starts weeping. In other words, it keeps it from looking like a haystack. The part that weeps is a cutting that is grafted high on the top of the rootstock. There should be a distinct difference in the bark and there should be a scar where the two compatible plants joined and healed together. If your vertical sprout is a part of the graft it won't grow far before it begins to weep again on its own. However, if the vertical sprout emanatates from below the graft then it will continue growing vertically and will become bigger and bigger in girth and the weeping part will live a few more years but stop growing. It's a shame to buy an expensive tree like that and not know what needs pruning and why. And we call ourselves Master Gardeners. (Sorry about that last comment but there is another post where people are debating the term Master Gardener)

mg60, thanks for the info I will pass it along to the lady.

Leasa

I've been a MGer since '03 and at the time I took the course it was understood that the emphasis was 'where to find' information rather than making me a 'green know it all' in 10 weeks. I enjoy my activity as a MGer and owe no apology to anyone for my ignorance in any area.
Eddie, the real shame is the MGers that enjoy putting someone down.
I'll bet you are ugly too!!!!!!!!!!!! and fat.
Lynn

To all: I'm not too fat or real ugly but I am stupid. I KNEW I should not have added that last comment but couldn't stop myself. It did not correctly express what I wanted to say.

I have had this happen to my weeping cherry tree many times.

I was worried at first but I just "went for it" and cut off the vertical branches shooting up. I did it in the spring. No harm came to the tree. Maybe I was just lucky.