Growing Lilium rosthornii for seed
Jim McKenney (Thu, 04 Apr 2013 10:12:36 PDT)

Aaron  wrote "My plants usually flower in Aug-September in comparison to henryi which usually flowers in June. "

Aaron, I know you're south of here, but June seems very early for Lilium henryi. Here in USDA zone 7 Maryland, just north of Washington, D.C., it blooms in mid-July. 

Griffiths, writing about a century ago, noted that even plants growing in northern Virginia often did not ripen properly outside before freezes; he suggested cutting the stems and maturing them indoors in water. 

Jim McKenney