eriogonum red time

This is Eriogonum umbellatum (the sulfur buckwheat) when the flowers are at my favorite stage. The blooms start out bright canary yellow, and after a few weeks, turn to this brilliant combination of yellow and red. In another week or so, this stage will pass, and the flowers will fade to brown. It's a pretty good show for having received no water from me. It's a mystery, however, why this plant hasn't self-seeded. Other eriogonums self seed abundantly (some might even say weedily) in my yard, but I haven't seen a single seedling despite letting the seed heads stay on the plant until they shatter and disperse. I suppose it is a good thing, in terms of tidiness, but it makes me wonder.