This mini-guide to germinating cacti seeds is adapted from a method taught to me by an Arizona gentleman, who developed it from observing cacti seeds in nature. My first attempt to use it was in 2001. I refined it further in 2002 and here I describe the method I am currently using. I attempted to improve it further this year, but failed.
I am describing, with the help of numerous photographs, a method that works well in the cooler, duller climate of the United Kingdom. To old school purists, it may seem revolutionary. When it was first told to me, I felt the same. The quoted results forced me to try it, and I have never planted cacti seeds in any other way since. So, get a packet of the easier cacti seeds and give it a try. I would recommend any variety of Astrophytum. They are large seeds, they give large seedlings and germinate quickly.
I have used the method described here to grow many varieties of cacti from seed, including Astrophytum, Ariocarpus, Turbinicarpus, Lophophora, Mammillaria, Rebutia, Copiapoa, etc. It does not work well with the very small and slow growing seeds, such as Strombocactus, Aztekium and Blossfeldia.
This guide is based upon a sowing of twenty seeds of Astrophytum ornatum v. glabrescens, sown on the 5th April 2003.