Perhaps it is nothing to do with roots. Real oaks count on squirrels to spread their acorns, so at first the squirrels happly spread the acorns. However, since they are not nutritious they eventually all starve. Once there are no squirrels nearby, the spreading stops unless happenstance - water, humans, spreads one to where squirrels can again carry out their duty:) Go to Comment
Interestingly, it has the feel of the really old Arthur tales, both good and bad, light on the whys. Some of the things Merlin did not seem to make sense with what was described in the tale.
So, it was a nice sword that resisted being turned to junk by the Wizard, and then to stop the battle (since it would I guess cause lots of collateral damage?) this third party sucked himself, the knight and the evil wizard into the blade?
Now the blade will draw energy to the trapped Evil Wizard, while the 'good' wizard will try and stop this by strengthening the wielder's tie to the weapon?