Ask Mr. Smarty Plants

If the pods were still green when you took them off the stalk, they came off too soon. They need to be black or very dark brown and starting to show signs of splitting before they are ready to be removed from the plant.

We have discovered that there is one yucca native to North America that can grow in climates that would not ordinarily be considered yucca country; that is, not desert. Yucca filamentosa (Adam's needle) does, indeed appear naturally in Illinois. We will assume that is the yucca you have, as the propagation instructions should be pretty similar across the genus Yucca. If you follow the above link to our Native Plant Database webpage on that yucca, you will find these propagation instructions:

Description: Yuccas will germinate promptly from fresh seed held over winter. Seeds germinate best in 60-70 degree temperatures. Yuccas may also be grown from rhizomes, stem cuttings, or by digging offsets from the side of established plants.

Seed Collection: Gather capsules as they begin to dry but before they split. Allow to dry, then crush to remove seeds. Overwinter, keep seeds in moist sand in the refrigerator. For longer storage periods, keep in sealed, refrigerated containers.

At the Lady Bird Johnson Wildflower Center, we have collected and prepared yucca seeds for the Millennium Seed Bank. Crushing the pod to remove seeds is not as easy as it sounds. We found that pliers worked about as well as anything, but it was a struggle, either way. Inside the broken pod, you will find channels of seeds. They are flat, black wafers, very thin. As you pull out a stack of them, you may find a neat, round hole drilled up the center. This is the nursery for the larvae of the yucca moth, who have been munching on the seeds. However, the yucca moth is essential for the blooming of the plant. Again, from the webpage:

"Yuccas depend on the Yucca Moth as their agent of pollination, and these moths depend on yuccas for food. At flowering time the female moth gathers a mass of pollen from the anthers of the yucca and then flies to another yucca flower, where she deposits a number of eggs into the ovary among the ovules (immature seeds). Next, she places the pollen mass on the stigma of the flower, thus ensuring pollination and subsequent development of the ovules into seeds. As the seeds enlarge, they become the food source for the moth larvae. Many of the seeds remain uninjured and are eventually dispersed, potentially producing new plants. At maturity, the larvae leave the seed capsule, drop to the ground, and pupate. The adult moth emerges next season as the yuccas begin to flower."

No, the seeds with holes in them are not viable, but the yucca puts out LOTS of seeds, so you'll find some intact seeds, just persevere. This Floral Genome Project on Yucca filamentosa has some more information and pictures of the seed (greatly magnified). Even if you have some other species of the genus Yucca that you have somehow convinced they are living in deserts in Illinois, the propagation instructions will be the same.

Yucca filamentosa