Ripe Chestnuts Fall After Autumn Rain - Chestnuts And Spiny Burrs, Closed And Open, Fall From A Tree After An Autumn Rain. Fallen Chestnuts Are Ready For Harvest And Roasting. Chestnuts Are A Tree Nut, That Ripen, Usually With Three Nuts Enclosed In Each Spiny Green Burr And Lined In Tan Velvet. The Nuts Ripen, The Round Burrs Open And Fall To The Ground At The Time Of Early Autumn Frosts. Photo