Busy Wasps

Our neighbour has the most amazing garden and she approached us in the spring asking if we wanted to use it. She's got too much going on to take on the entire garden and so we totally jumped at the opportunity. Her husband rototilled it for us and she made sure all the automatic underground watering was ready to go and all we had to do was plant. It's been so great!
We were over there a few nights ago when Brayden spotted a wasp nest in the apple tree beside the garden. Our neighbour was on her way out of town and left us with wasp spray after we offered to get rid of it while they were gone. Ryan went over there last night and sprayed the crap out of the nest and I guess he could hear it buzzing like crazy. Today we went over there in the afternoon to take it out of the tree and pulled the nest apart. Inside were all these wriggling larva growing. Gross. Now it's onto the next nest, it seems like there are about a half dozen nests started between the two of our places. I had always thought that they were territorial and didn't start a home where there was one already started but it looks like i'm going to have do some further research. How do you stop wasps from building their nests around your house?