If a prone tree fails the root roll, it can no longer blitz, even if the target is adjacent.

Saw this on TheSpyder's stream; his opponent had a prone tree lying next to Spyder's ball carrier. The opponent tried to blitz the ball carrier by selecting the prone tree and then clicking Spyder's ball carrier. He then failed the root roll, re-rolled it, and failed again. The tree succeeded the stand-up roll, but then was unable to complete the blitz. See this clip for the evidence:


BB2 Champion Ladder Admin Team

That's not a bug. See last sentence of the skill description:

Take Root (Extraordinary)
Immediately after declaring an Action with this player, roll a D6. On a 2 or
more, the player may take his Action as normal. On a 1, the player “takes
root”, and his MA is considered 0 until a drive ends, or he is Knocked
Down or Placed Prone (and no, players from his own team may not try
and block him in order to try to knock him down!). A player that has taken
root may not Go For It, be pushed back for any reason, or use any skill
that would allow him to move out of his current square or be Placed
Prone. The player may block adjacent players without following-up as
part of a Block Action however if a player fails his Take Root roll as part
of a Blitz Action he may not block that turn (he can still roll to stand up if
he is Prone).

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