Looks like a flowering cherry (Prunus sp) with a virus (aphid induced maybe ?)

Thanks for your answer Badfish. I'll look that up and see if it matches.

Do you say virus because of the wilting/weeping at the bottom?

Well the picture's so dark its impossible to tell where the straight trunk is growing from, so I don't know if its growing off the rootstock, or whether it arises from the weeping part and is merely reverted growth.

If it is a cherry, the weeping part is likely grafted onto a different rootstock - if that straight growth is coming from below ground, its off the rootstock, and isn't the grafted part, in which case, cut it off below ground, or as low as you can, without disturbing the other roots. If its arising from the main stem of the weeping part, remove it there, being careful not to damage the rest of the stem. If you don't do this, the weeping part will die, leaving whatever tree is being produced by whatever rootstock has been used - likely Prunus padus or similar.

At least, I think that's what's going on - for some reason, both photographs are quite dark, and its difficult to see properly.

Thanks Bamboo.

I'm not sure why the photos came through so dark, looked a lot lighter on my phone. I've added another.

Basically the main branch is the weeping one and the offshoot has now grown taller and straigher.

Can (and should) I just cut off the weeping bit as close to the branch off as I can?

Thanks

Looking at the last image I would say that you have had a standard weeping cherry at some time. The straight growth has come from the root stock well below the graft point. The way these trees are done is to graft the weeping part on to a tall stem from a different tree. The part you need to remove is the straight bit, right back to the point of origin. leaving the weeping bit alone.

Wow great info guys - thanks a lot.

I would never have known that the weeping part was grafted on. I probably would have chopped this bit off.

I actually thought that they looked like too different trees, because the density of leaves looks different, but I didn't know about grafting and I thought it might have been some sort of weird mutation.

So just to be sure, I should chop the straight bit off?

Is it likely that the weeping bit will grow taller?

Take the straight bit off, but be careful, you do not want to to too much damage to the trunk.
No, the whole idea of these weeping trees is that the height is fixed, to a large extent, by the height of the stem to which it is grafted. What will happen is that the weeping part should fill out and grow downwards towards the ground.

Hmm, that's what I said in the first place, Eastcoastgarden, cut off the straight part. Perhaps I wasn't clear enough...

Yeah sorry Bamboo, reading back I think I was just being a bit dim there. Thanks a lot for your advice, I'm learning a lot from everyones help here.

Well, it was quite a wordy answer, and these days, no one seems to read stuff, they just skim it, so maybe that's what happened. I should learn to type in bullet points to make it clearer! Doesn't matter either way, at least you know what to do...

How do I cut it off - can I just take my saw to it at the joint or do I need to be a bit more careful than that?

Ah, I see, its arisen from the main stem. You need to make a very clean cut (no jagged bits left behind when you're done) with a very sharp and very clean pruning saw, don't use a dirty one. And take it off as near the stem you want to keep as possible, leaving about quarter of an inch still attached to the tree. This isn't ideal, because youi don't want the straight part to grow again, but its too dodgy to take it any closer to the stem you want to keep. Make a cut upwards first, then do the downward one, and support the straight trunk till its detached, otherwise there's a risk it'll tear away from the other trunk/stem you want to keep. YOu might be best off going and buying some Arbrex or other wound paint - it isn't recommended on most trees any more, but for cherries, it does help to prevent silverleaf disease from entering the wound.

Agree!