Follow up question,

instead of doing 3 seperate beds, can I mix them together in a "L" shapped box with the same dimensions, 20'x4' for each section? One planted near the outer edge of each of the "L" legs and one in the center.

Thanks

I have three types in a 6 x 60 bed. I just dig a trench where I want them seperated. I didn't bother with rhizome barrier because I have access to all sides. I just finished root pruning. Nothing appears to have left the raised bed; I had a rather large atrovaginata rhizome that was heading into the Spectabilis though.

UNfortunately, I beleive I have to do a barrier as I live in a subdivision and my neighbors would not be the happiest with the invasion. But thank you for the confirmation that I can do all three types in the same bed. That helps me out alot.

You're right about the depth, it isn't necessary to go deeper than 20 inches. Trust me, every inch deeper you go mean a tremendous extra effort (especially given the scope of your project).
Your local nursery gave you some bad advice, this material is among the strongest known to man. No rhizome can even come close to breaking it.

My best advice is to make move of an overlap. I have three seperate sections enclosed in a barrier and two have 'escaped' by exploiting the gap where the barrier overlaps. Also, you can't really glue the material together, so a long overlap helps compensate.

Thanks Suprdude. Sounds like I am right on track on this one. I figure on the overlap, 4'-5' should do it. I'll use the double sided tape that it comes with and then was going to use a couple alumn. mounting strips, one on each side, for the lenght of the barrier and screw them together with some large washers to pressure hold the seam near the edges closed. Thought if I angled the barrier slightly, perhaps 15 degrees or so, in an up and out way "/" that it would deflect any rhizomes towards the surface and I could simply cut them when the break the surface near the border.

Being in a subdivision doesn't eliminate root pruning as a control method. You just have to leave enough room (~18") to work between your grove and the area you don't want it to spread. I installed barrier at my last house in a small bed and I'd much rather root prune!

I dont have a problem with root pruning as it sure is easier than digging a 24" deep trench for nearly 100'. I just want to make sure that I dont ahve a problem with my neighbors cause of spreading.

How difficult is it to control by root pruning? My biggest concern is that I dont see anything for a year or 2 and then all of a sudden, 20' away in my neighbors yard, I see a shoot coming up and now have awhole bunch of pruning to do.

It really depends on how you will prepare the beds. I recommend that you create a raised bed by covering the existing sod with a layer of newspaper (you could use Roundup) and then more top soil. 3-4 inches on top of what you already have should be sufficient. Add another good layer of shredded hardwood for mulch. Where it meets the grass, use a spade to cut a clean line through the sod. Then each fall clean up the sod line with the spade going as deep as your spade will go. You will see many of the rhizomes as they leave the raised bed and can cut them with pruning shears.

If (when?) you miss one and see something shooting out of bounds, don't just rip it out of the sod. Cut a slit in the sod as you follow the rhizome and remove. After a good watering and a couple of days, you won't even know the sod was disturbed.