may i make a suggestion, just for where i am, i used the "mogie" method and its basically same unit, you can find it in DIY section of riu, anyway my main reason for going fencpost is i only found small amount of 6inch PVC and it was shedule 40, $50 for a 10' and the caps were 30bucks each cus they are rare so i went with 4inch PVC and had great results, take it from a guy who built 2 differenct styles of system, the square fencepost hold more volume for roots and are easy to keep up right, round gully units like these need to be paid good attention to when fastening down, fence posts need no fastening, thos drainage elbows if available is 6" must be very pricey, they are around $20 for 4", performance wise they are certainly equals, but it cost me 4 times asmuch than fencepost method, lowes has 7' and 98" for $18 and $23, 4inch pvc at home depot is $9 for 10', also i know i hit on the plants likeing to tip cus of the curvature, but since the plants site or hole you cut out is also on a curve, the plant stem and all will want to lean over, as compared to the flat side of the posts, thank you for letting me voice my opion on your thread bro