Not an expert at all but it looks like you can prune it in either spring or fall. https://www.nature-and-garden.com/gardening/russian-olive.html

Thanks, gardenchloe. I saw that article as well, but I saw others saying it's best to wait until late winter or early spring as the healing from the cuts will do better at that time. Since it needs more than light pruning, I'm thinking of waiting - although we had to do our Honey Locust tree last Sept. before we had a new roof put on, and it did fine.

As long as the tree is dormant, it can be pruned. We're not there yet. How great is this weather, by the way? It almost makes up for the horrid summer!

I would not wait for new growth in spring, I'd do it sooner than that. Maybe a November to March time frame. One thing to consider is the availability of your trimmer. It seems like they're busier in the spring, cleaning up after our spring storms, which might delay your time frame into a not so great time for extensive work.

When you say drastic pruning, how drastic? Topping? Removing large branches?

Thanks treebarb. It has quite a few dead branches, and some branches overhanging our neighbors yard. So some good sized branches need to come off. Your time frame fits into some that I read - Feb. to mid-March - so think we'll wait until then to give it's best chances.