[R] How to hide tick lines behind the "box-and-whisker" 's in a boxplot

[Helmer Belbo]

Dear R people,

I wonder how to hide tick lines behind other figures in a plot, e.g.
in a boxplot.

# Sample code:

x<- c(rep(4,50),rep(5,20),rep(6,50),rnorm(20,5,1))
boxplot(x)
axis(2,tck=1,col.ticks='grey',lty=5 )

# end of sample code

The tick lines is put on top of the box-plot, but I would like to put
these lines behind the box and whiskers..

Regards
Helmer