If you queue multiple actions to plant hedges to the same border on accident, after planting the first hedge there appears to be no flag to halt succeeding actions in the queue to attempt to plant hedges on that border.
This results in the loss of sprouts to a tile border that already has a hedge created on it.
Additionally if you try to plant two different hedge types, it will keep the first one planted and take the sprouts attempting to be planted of the second type with no change.
EDIT: This works the same way for flowerbeds, lot of materials lost in that one...