Question
I have 2 yukka plants and the stauks have large seeds on them and wonder how to plant the seed to make additional plants, thanks bob

Answer
Robert,

The seeds are not ripe until the pod turns brown. I have several yucca plants but have never tried growing them from seed. They produce babies (off shoots) so easily that I find it easier to dig up a baby with as much roots as possible and plant that where I want a new plant.

However, the sight below has complete instructions on growing them from seed.  

http://www.bennyskaktus.dk/propagat_UK.htm#yucca_seed

Good luck.
Darlene