would this work or cause more problems than it's worth? Ie drainage and such I'm putting in two large raised beds, but to account for root space I was going to dig them in little trenches, weed barrier them then overfill with a soil / compost mix so although the edging to the raised border is only 15cm high, they get approx 25-30cm of root space More trouble than it's worth or will it work?
I didn't bother with this with my raised beds. The sleepers were put in place, and the soil was just dumped on top. Seems to have worked out ok for me.
