I haven't found a single commercial source of seed for it, and I tried traded seed from three different source last year, with zero germination. I think the key is to find a trader in a very warm zone, 9 or higher, and have them wait quite a while after the bloom to collect seed. Plants from colder zones won't have a long enough season to set and ripen seed.

You are unlikely to find a source for this as the cultivars 'Rubrum' and 'Rubrum Dwarf' seldom set viable seed and are generally considered sterile cultivars, even in warmer zones where this grass is fully hardy. I'd be skeptical of noncommercial online sources that offer this seed, as it will most likely be sterile or from unnamed forms and may not have the intense coloring of these cultivars as well as a tendency towards invasiveness. Most commerical growing is done from small divisions/plugs.

I don't think there would be a problem with invasiveness in cooler climates like mine and definately not in Lisa's. From what I read, it's totally frost intolerant. Since species P. setaceum can be such a heavy self-seeder in warmer climates, it should be possible to find good seed, if you can connect with a knowledgeable grower. I searched the exchange listings, and found only 2 traders in warmer zones than 8. Checking my records from last year, one batch of seeds came from zone 8, and the others from cooler zones, so my seeds probably weren't ripe.

It's interesting to note that Darke says that 'Rubrum' and 'Eaton Canyon' may not belong to the species at all. Such a fascinating group of plants, these grasses, and so little information on the web for them. I'd like to see long-known growers like Bluemel, and Jim at Bluestem, publish some stuff on their experiences.

Donn, that is the SPECIES setaceum, not the two named cultivars. P. setaceum is widely naturalized in warmer climates, like California, to the point of being an invasive nuisance, however the purple forms are not. And yes, there is some thought that these are really of the species P. macrostachyum, another extremely tender and freely seeding species except for the purple/burgundy colored forms. Another noted OG expert and grower, John Greenlee, has a nursery located in southern California (Santa Monica) and even he concedes these two cultivars seldom will produce viable seeds. One might continue to experiment with seeds obtained in trades from high zone growers, but I would be very reluctant to pay good money for seeds which are unlikely to ever germinate.

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Sorry, I didn't see 'Rubrum' in Lisa's question. I thought she was asking about P.s. species. My mistake. Last year, I was looking for species, because I like the color of the blooms.