well you can try cutting it off close to the main trunk, pot it up and keep fingers crossed. remember to keep it well watered.

You could try layering it instead. Make a cut in the bark on the underside and peg it down so the cut is under the soil.
For more detail try this site
https://www.google.co.uk/?gws_rd=ssl#q=layering+trees

Most Magnolias are grafted so even if you do manage to root this sucker it could be 'pot luck' as to what you may end up with.

Yes, if it is a seedling rootstock, it may take 20 years to bloom.

Great advice as always! Was going to try air layering (great suggestion with the properties of the plant) but if they are typically grafted plants than buh bye! Thanks!

Can anybody see the graft junction? They aren't usually below the ground or am I wrong?

I think that I see it just an inch or two above ground level, where the trunk thickness and bark texture suddenly change. If it was sold as a named variety, it was almost certainly grafted.

Wow, that's a practised eye you have Tug. I thought that was just soil sticking to the bark.

I thought that that might be possible, too, so I'm putting more weight on the shape of the base, which is typical of grafted trees of all sorts.

Tug, I looked up close and indeed has a different bark texture that spot down, definitely a graft! Nice catch there on probably a 25 year old tree.