Conclusion to the first three experiments

All 13 plants eventually withered and died.  Once they'd died I cleaned the soil off and found that none of them had put down roots, that the shooting tip of a Rubus plant has the power for upward growth but not downward growth.

This is good.  I know something about brambles now that I didn't know before.  As they say: failure is always an option.

Moving forward then.  For the next batch of experiments (2014 at the earliest) I'll need to graft a shoot onto a root before burying.  Grafting on that sort of small scale is incredibly fiddly and up to now I've only ever made one plant graft in my life.  For now then, I suppose I had better get some practice in.