Our sophora Japonica is 30+ years old and is planted in our backyard. As you know, after 10-15 years, these trees drop their yellowish flowers in August, followed by the seed pods. Every year the flowers and pods are more numerous and the entire yard and deck become covered with these annoying droppings. Is there any way to prune the tree in time to prevent this occurrence? Is there a better tree to replace the S. Japonicum at this point in it's (and our) life?
The Sophora japonica is a beautiful tree and grows well in our environment, but you do need to clean up under it regularly. I don't know how you could prune one to prevent the blossoms short of removing flower buds in the summer before bloom. It blooms on new growth so pruning in new growth off in early summer would certainly reduce blossom formation, but that could be difficult and time-consuming in a mature tree and I imagine yours at 30+ years old is getting fairly large.
Any replacement tree would of necessity be much smaller than your now pretty mature tree. It would be several years after planting before it would be providing significant shade in your yard and deck. And of course, you wouold want to take into consideration the cost of removal of the existing tree which could be considerable if it is (as I'm imaging) pretty large and if the location has difficult access.
That said, some alternatives that would provide shade at maturity without the mess of the Saphora are maples, both silver and red provide good color and do well here, Oregon ash, zelkova, honey locust, and the seedless variety of sweet gum (make sure you get the seedless variety otherwise you'll just trade one mess for another).