Another useful plant from Buchanan's A Weaver's Garden
Page 139: Nuts from horse chestnuts give saponin for washing wool, apparently with no need to process or add anything. Perhaps you need to chop the chestnuts, I don't know.
I used to be very sad that the glossy nuts littering the streets of Cook Street Village in Victoria and the Old City Quarter in Nanaimo were inedible. Now I know what they can be used for.