  Let $e,r \ge 0$ be integers and let $\mathbb{F}_e : =
\mathbb{P}(\mathcal{O}_{\mathbb{P}^1} \oplus \mathcal{O}_{\mathbb{P}^1}(-e))$
denote the Hirzebruch surface with invariant $e$. We compute the Seshadri
constants of an ample line bundle at an arbitrary point of the $r$-point
blow-up of $\mathbb{F}_e$ when $r \leq e-1$ and at a very general point when
$r=e$ or $r=e+1$. We also discuss several conjectures on linear systems of
curves on the blow-up of $\mathbb{F}_e$ at $r$ very general points.
