What was there response to your suggestion to remove the trees? Are they lazy? confused? physically unable to do this? Can you offer to help remove the trees?
Do they like the trees? In that case, is there even enough room along the fence to support 4 additional trees? You might want to point out that such crowded trees can become a hazard that a potential buyer of their home might not want to deal with.

I had suggested that I pay to remove the walnut trees and had mentioned the negative effects walnuts have on other plants within the walnut root zone. They had already seen the problems because everything had died on their side of the fence. But the male of the family said he liked the trees and there weren't enough trees on their lot. In fact, when I had tree trimmers work on my trees, he stood and watched them the whole time they were working on the walnut trees to make sure they didn't do anything bad to them, I think (I had told him I was going to have the limbs trimmed back that were on my property because of what the walnuts would do to my metal roof). I had also mentioned the issue with maple tree roots on their garage floor and pointed out my badly cracked driveway as an example. He simply said that he didn't want to take down any trees that decided to grow on his lot.

I won't bring it up again to him. I would say he likes the trees. He doesn't seem too handy with household stuff. Maybe I'll mention to the wife about hazards when they think of selling the house. Frankly I don't want them to sell the house. It's hard to get good neighbors and aside from the excess trees and the perennial morning glory (didn't even want to think about that right now) issue, I really like them. Hmmm maybe I'm talking myself out of this problem -- have to think about that.

Try contacting every real estate agent in your geographic region. Explain to the agents that you and possibly your neighbor (if they can interest or encourage them) may be interested in selling your homes and to please mail both of you information about what other homes are selling for in the neighborhood. This will bombard your neighbors with mail from real estate agents and plant the idea of possible relocation into their minds.

Also ask them for a free appraisal of your property and appraisal of your neighbors property for comparison. When they come out to visit you, explain that you understand that the neighbors tree shade will affect the price you could get from your property. Then ask them if they know of any way to apply pressure to the neighbors so they might remove some of their trees. If they contact your neighbors, they will probably emphasize to them the damage their trees have on potential future sale of their property.

The real estate agents are experienced in this area and would probably be able to supply you with the best options to pursue.

However, don't underestimate the value of your own property.

Thank you for your suggestions -- you certainly gave me a perspective I hadn't considered. I may have to wait until the real estate market heats up again -- we are losing our biggest corporate employer (about 4000 employees) this year and it has truly become a buyer's market.

your neighbor sounds like my stepdad. he refuses to remove any tree that is healthy. and as he has told me each time i try to get him to remove a problem pecan tree, it is HIS LAND AND HIS TREE.

sorry, but as long as your neighbor wants to keep the trees you just have to live with it or move.

around here we love when trees shade the lawn, of course we also have temps in the upper 90's to low 100's from late may to october.

Yes, I know there are few options for issues like this. I think I just needed to vent. I have a couple of more years before the sun disappears from my property. And I do love hostas and heucheras.

I have neighbors on both sides of me that have huge clumps of Eucalyptus trees growing two feet from the property line, with the branches hanging over my property. The previous owner on one side had had the clump topped to about 30 feet tall, but now there is a new owner whose wife says she likes the monstrosity and it has grown back to sixty feet tall in just a few years. On the other side the owner cut the tree down one time, but it resprouted as multiple trunks and he is now letting it grow, now about 40 feet tall in just a few years. Two of the trees in the clump blew down during a storm, unfortunately it wasn't the four remaining ones that are leaning over the fence. These Eucs will grow to maybe 80 to 100 feet tall with a spread of almost that much. When that happens the branches from both sides will meet in the middle of my 50 foot wide lot and completely block out the sun and I will have to give up gardening and my semidwarf fruit trees will all die. I bought a 14 foot long pole saw and cut off all the branches I can reach, but the one that are higher than 20 feet off the ground are beyond my reach.