Grafting Plum trees

We have quite a few plum trees on site 20+. About 4 are great eaters and cookers . Others not so good I suspect suckers from the good ones rootstock.
Has anyone tried grafting plums with mature trees ?

David

I grafted onto some old and not very vigorous plum trees this spring. In spite of sub-optimal conditions, 6 out of 7 grafts have taken.
I select the youngest and healthiest looking branches for my grafting.

I'v grafted Japanese plums with great success on peach, almond, and apricot rootstock. The largest diameter branch though that I was grafting was less than 10mm. Cleft grafting might work best for you, but that personally has not worked for me. My greatest success is with whip grafts, followed by bud grafting (in peach). You might try all three methods side by side on the same tree and see what works for your hands. Do this in the winter once the trees have lost their leaves and have gone dormant. Expect to see the grafts budding out 3-4 weeks AFTER the remainder of the tree starts to leave out the following spring.