I believe they are the asclepias that need to be moist stratified. They probably dried out to much. I usually lay them on the moist soil - then gently sprinkle a thin layer of the mix over them - then wet it all down if any of the seed is showing repeat - keep the bed moist - should have sprouts within 10 days.

cheers

They need to be cold, moist stratified which means storing moist -- I use a moist paper towel in a baggie or moist vermiculite in a baggie. All seeds need to absorb moisture in order to germinate. So the silica gel was the wrong thing to use.

However, asclepias are slow to germinate. Keep the seed trays moist and you may find they come out in the next month. If not, store the seed trays in a cool place for the winter or outdoors under straw and you may get germination next spring.

The silica gel may have dried them out so much that they may never germinate??? I would probably throw those seeds out and get different ones. They should be easy to find.

I use moist sand in a ziploc bag when I cold stratify.

I keep the container dry to prevent fungus from ruining the seeds (mostly vegetable) I am storing. I guess I will just collect milkweed seeds again this fall and spread them out in the yard where I would like them to grow. Nature should do a better job of germinating them than I did.

The winter sowing method works really well for common milkweed. I just stored mine in a baggie in the cabinet until February and then winter sowed (outside in a container with a clear vented lid) and got nearly 100% germination. I've had the best luck when using containers that are at least 3 inches deep. It works like spreading them out in the yard but keeps critters from eating the seeds over winter, and easier to keep track of where the seedlings are - especially helpful if the seedlings are hard to differentiate from weeds.

Here is a link that might be useful: Winter Sowing forum