Sitemaps and Seo Plugin

Hello i have a simple question about the google sitemaps and seo plugin:

How will Google find all the sitemaps? for the main blog its easy, i can go to google webmaster tools and input the url for my main sitemap.xml mydomain.com/sitemap.xml.

however how will google find all other registered blog´s sitemaps?
as i see it generates one sitemap for each blog:

myblog.mydomain.com/sitemap.xml

i should not have to input all sitemaps into google webmaster tools?

is there something im missing?

Regards Roger