  We find the collapse of columns of granular rods to show range of behaviors
that depends on particle aspect ratio (length $L$ to diameter $d$) and initial
pile geometry (height/radius). For all aspect ratios $L/d$ below 24 there
exists a critical height at $L/4$ below which the pile acts as a solid,
maintaining its initial shape, and a second critical height at $3L/4$ above
which the pile always collapses like an ordinary granular material. Separating
the critical heights is a transition region in which the probability of
collapse increases linearly from 0 to 1. This behavior is independent of
particle length, width, or aspect ratio. When the pile does collapse, the
runoff radius $r_f$ scales as a power-law with dimensionless height $\tilde H$,
agreeing with previous experiments on ordinary sand. For low piles the scaling
is linear, with $r_f\sim \tilde H^{1.2\pm 0.1}$. Above a critical pile aspect
ratio (pile height/radius) this switches to a square-root scaling, with
$H^{0.6\pm0.1}$.
