Looking for stooling or sometimes called mounding rings. Ideally they should be round, stackable and split with a hinge on one side. I could make some out of a 55 gallon drum. but they would be steel and would need lots primer and paint for longevity.
Thanks 
Just use chicken wire fastened into a circle as big as you want, line the exterior with cardboard to hold your soil medium inside, then you can add soil medium as high as you wish!
Dennis
Kent, wa
Good timing on your post.
I can’t help directly but I literally just came in from planting out two rootstock I will be trying to propagate.
I planted mine in the ground flush, but my thought is not to do anything overly complicated or expensive. Perhaps just some gardening landscape edging and stack them. Put a little straw or mulch on the edge to keep the soil in.
Other option would be to use a fire ring and add the soil as needed. I have several box store bought 36" by 12" high. I need to grow mine out another year before I head it to push new laterals, so I’m two summers away from needing to add soil.
This is a shot of the fire ring I was appealing of.
plastic covert pipe cut to length, split and hinged may work, didn’t think of that…
Thanks
