Question about stripchart

I have E. coli data (variable ?conc?) for 73 dates over months from Apr through Dec (variable ?monames?).  The data are in order from the April through December, and are in a data.frame titled "monamescon?.  When I run stripchart(conc~monames, data=monamescon, vert=TRUE), the months come out in alphabetical order along the x axis.  How can I get them to come out in time order instead?