I am no good at straight lines, maybe because mathematics are just not my ''thing'' and so I decided it would be best to enlist assistance from Zigs, and I'm so glad I did.
But your green thumb makes up for any lacks! For our flower beds, we dig a 6" to 8" trench along the outer perimeter, and that keeps grass from encroaching. It's easy to take a spade and cut off any grass strands. Love your gardens!
I didn't notice the lines in your garden as I was too busy looking at all the lovely plants you have. Now that you've pointed them out I can see what a great job Zigs has done. You obviously compliment each other and have a garden to be proud of.