How & when is the best time to trim a large old flowering tree?

I'm not a tree expert but I trim my trees in the fall when they are dormant.

I don't blame you it's best to be safe. I would call a nursery and ask them. They usually have more knowledge on the specifics, or you could look at some how to videos on the internet. If you know the type of tree you have the internet probably has a video on pruning it. Now days they have how to videos on almost everything. Good luck!

Hi Audrey,

I suggest that you prune lightly at first. Cut the longer branches back to a knot in the wood. When you cut, realize that the tree will probably grow 2 or more branches where you cut. That's why you look for the knot. The best time to trim depends on when the bush flowers. Here's a great article that explains when to trim which kind of bloomer. I'd start with the longest branches and see what happens next year if you don't know what kind of tree you have. If you know the tree, you can look up specific information. Wishing you the best.

https://www.thespruce.com/flowering-trees-and-shrubs-1403319

What kind of tree is it? Pruning at the wrong time can kill the tree.