  We discuss estimates on the number $N_-(\alpha)$ of negative eigenvalues of
the Schr\"odinger operator $-\Delta-\alpha V$ on regular metric trees, as
depending on the properties of the potential $V\ge 0$ and on the value of the
large parameter $\alpha$. We obtain conditions on $V$ guaranteeing the behavior
$N_-(\alpha)=O(\alpha^p)$ for any given $p\ge 1/2$. For a special class of
trees we show that these conditions are not only sufficient but also necessary.
For $p>1/2$ the order-sharp estimates involve a (quasi-)norm of $V$ in some
`weak' $L_p$- or $\ell_p(L_1)$-space. We show that the results can be easily
derived from the ones of an earlier paper by Naimark and the author, Proc.
London Math. Soc. (3) 80 (2000), 690-724.
  The results considerably improve the estimates found in the recent paper by
Ekholm, Frank, and Kova\v{r}\'{i}k, arXive:0710.5500.
