Spider plant propagation

[Sean Ebert]

About 6 months ago, I propagated 3 baby spider plants.  They sit beside me 
now, about 15 inches high, each having about 15-20 leafs..

I'm patiently waiting for new babies to arrive, so I can propogate some 
"grand-kids", but I think these plants are using some type of contraceptive 
or something, cause there's no sign of any babies; all I ever get is 
more leaves!

I want spidy-kids!  Any ideas on getting these plants pregnant?  (Is 
there such a thing as "spidy-aphrodisiacs"?  haha!)

What acts as a good "growth stimulator?"     --thanks