Since they can grow as wide as 6-8 feet - and that is in diameter/a full circle - you do not want to plant them any closer to the fence than half that spread. So at a minimum of 3 feet away but I would allow an extra foot to be able to maintain the fence as necessary.

Thanks for the advice. The fence is an HOA fence with common area on other side. But it sounds like 3 ft is safe. Thanks again.

Depends on if you don't mind them touching or growing over the fence. If no, then AT LEAST 6 feet away. Even then you may have to shear after 5 to 8 years, or selectively prune some branches.

Thanks Dave. I do not mind if they touch the fence, just wasnt sure if touching the fence would affect or harm growth or the backside of the plant.

Since you're planting them not as a hedge but to allow for natural growth, you might consider positioning them a bit further than 18 inches, perhaps around 2 to 3 feet from the fence. This distance will give them ample room to mature, ensuring that their roots and branches don't interfere with the fence structure. Additionally, it helps in maintaining the integrity of your fence by preventing any damage from the roots or branches pressing against it as the plants grow.

Thanks for the advice Jordan! As of now, I am thinking 3 feet away from the fence, and they will be spaced about 8 feet between each, along the fence.