Ask Mr. Smarty Plants

There are 20 members of the Rudbeckia genus native to North America, of which 11 are native to Arkansas. However, this USDA Plant Profile Map shows that Rudbeckia maxima (Giant coneflower) is only native to 3 counties on the western edge of Arkansas, clear across the state from Cross County, so you may have harvested seeds from a very similar species or even from a hybrid. However, it really doesn't matter too much, they are closely related enough that if we can find propagation instructions they should be applicable to any of the Rudbeckia species.

Our webpage on R. maxima did not have propagation instructions on it, but the page on R. hirta, also native to Arkansas, had these instructions:

"Propagation

Propagation Material: Seeds
Description: Propagates very easily from seed sown in fall or spring. Spring-sown seed should be stratified. Rake seed into a loose topsoil or cover with ¼ to ½ inch of soil or mulch. If possible, supplement with water if fall or spring rains are infrequent and light. The seed requires several days of moisture and should germinate in one to two weeks.
Seed Collection: The nutlets turn charcoal-gray at maturity, usually 3-4 weeks after the bloom period. Seeds are mature at this time, but they are easier to collect after cones lose their tight compact stucture. Store dry in sealed, refrigerated containers.
Seed Treatment: Stratify for 3 months at 40 degrees.
Commercially Avail: yes
Maintenance: Black-eyed Susans are drought tolerant but respond well to an occasional watering. Additional irrigation in a dry year will improve the density of the stand and lengthen the flowering season. Do not mow until after the plants have formed mature seed cones, about three to four weeks after flowering. (Check by breaking a cone open and if the seeds are dark, they are mature.) The number of volunteer plants can be limited by removing the seed heads after the flowers are done."

Since this member of the Mr. Smarty Plants Team has no personal experience with cold stratification of seeds, we found these instructions from Wildones.org. Hopefully, you will find the method that works best for you.