Hello, Olin, Most of the door yard macadamia trees I see are single trees, and all seem to bear nuts. I was visiting in La Jolla two years ago in the fall, and saw a macadamia "bush" at the home of my friend's elderly relative, and it was sagging under the weight of all the nuts. A friend of ours in our church choir lives in Venice, CA, and had a large crop of nuts last year, and she only has one tree. I imagine if one had another tree, the odds would be upped that the very inconspicuous blossoms would be fertilized; but, then, again, the Fuyu has blossoms which are just about as inconspicuous as a macadamia's, the only difference being that the racemes of flowers on the mac may well be within the canopy of the tree, since it puts out fruiting spurs on wood that is already a year old, and may well be leaf covered. That is the chief reason, I believe, that the buzzword in macadamia circles is "canopy management." Good growing to you! Ron