Trees in a row

I need to place a lot of trees in rows, like in an orchard or in a vineyard; what’s the easiest way?
I tried the foliage but it seems I can’t place instances along a single axes… or no???

I actually haven’t tried … but could you not attach the trees to a spline and place your spline on the map. I recall something similar to this being done … but I can’t for the life of me find the thread or the post.

Thanks, how can I attach something to a spline? Can you give me dome references?