Anyone know anything about Gleditsia trees that are dead from halfway upwards?

is there a graft point? if shoots above graft cut out the dead bits and the tree will grow and flower as it was last year. In time it will become 'normal'
if below the graft then it will still grow but not be the same variety. again cut out the dead bits there is no point leaving them on.

I think you'll find that the 'yellow blossom' is actually foliage on new branches starting into growth. If it is 'Sunburst' it is not as bone hardy as is said and has probably been damaged by this winters cold. Prune off all the dead branches and it should recover.

I can't see a graft point. It was an attractively shaped tree, just a bit spindly. Now, if I cut off all the dead bits, which is every single branch, I will be left with a thin stick with yellow flowers on basically, but I don't think there's much else I can do. So suppose I do this, and the side shoots are new branches, they are all now quite low, like from 4" off the bottom up to 4 foot high. What is the best way to grow a "normal" height tree again, or do I have to accept I will have, at best, a bush?

you can raise the canopy by removing the lower branches as and when. probably better after it has flowered.

OK, will give it a go! Thanks for the replies.

I had a gleditsia for a lot of years, in its infancy and at approximately two yrs old it was transplanted twice, believe me, these trees as beautiful as they are and as fragile as they initially look, are indeed very hardy..I doubt very much whether your tree is dead and would urge you to be patient. After transplant the first time, this tree that graced my garden where I once lived, showed decline, then it regenerated itself, second time it was actually damaged big time when an upturned 3'x2' paving stone fell on it, and still it fought its way back to become the strapping 30' tree it still is today. .