We are just about to plant a large number of plants on a steep slope. I intend to be very careful about spacing the plants after needing to remove every second plant the last owners planted because they were too close together.

I think this is a pretty easy question, but I want to confirm.

If I have a plant that will get 3ft in diameter, I measure 3 feet flat, not three feet down the slope. (If you picture an upside down right angle triangle, I am measuring the flat top part, not the long angled side.)

Thanks!