Different Type Of Tree Growing From Established Tree

sylvieathome

Hello everyone,
Just wondering if you could help please. I'm a novice gardener so I don't know a huge amount. 
There is a tree in my garden which is not evergreen, has green leaves and produces helicopter seeds at the end of summer (first photo).

There is a small trunk growing from the base of this tree. You can see this in the last photo, on the left hand side. (Please excuse the Spanish bluebells, they were here when we bought the house.) This new trunk has variegated leaves (second photo) which also fall in the autumn. I don't think that the variegated leaf tree trunk produces seeds.

Could someone help me identify the established tree with green leaves and should I cut off the new variegated leaf trunk from the established tree? Should I just saw it off as cleanly as I can? Would cutting it off benefit the established tree?
Thank you for taking a look.
Sylvie 

Alan Clark2 in Liverpool

The tree is a variegated Acer. These can revert to plain green, so you should cut off any branches that do, leaving only variegated leaves.

sylvieathome

Alan Clark2 in Liverpool said:

The tree is a variegated Acer. These can revert to plain green, so you should cut off any branches that do, leaving only variegated leaves.

Oh dear. The previous owners didn't do much to the tree and now all of it is plain green. It's very tall and practically impossible to cut down. Should I leave the new growth? 

Alan Clark2 in Liverpool

If you let it grow it will eventually become a much larger tree, so I would cut down the green part regardless, unless you actually want a large plain acer! It shouldn't be too difficult if you do it now, although it would involve some work. I would start by cutting the top off, a little above the fence, with a saw or pruning knife, then cut the trunk near the base. 

sylvieathome

Thank you for your help Alan, we will have to get this sorted asap. I appreciate your advice very much. 
Sylvie