ROOTING OF APPLE, RHODODENDRON, AND MOUNTAIN LAUREL CUTTINGS FROM STOCK PLANTS ETIOLATED UNDER 2 TEMPERATURES

Dormant stock plants of apple (Malus domestica Borkh.) rootstocks M.26 and Ottawa 3; Rhododendron 'Britannia', 'Purple Splendour', and 'Unkn own Warrior'; and mountain laurel (Kalmia latifolia L.) 'Ostbo Red' an d seedlings were forced to grow at 18 or 28 degrees C in continuous da rkness or 14-h photoperiods. Etiolated shoots were then acclimated to light with or without aluminum fail wrapped around their bases to keep the bases etiolated. Shoots forced in diurnal light were neither etio lated nor wrapped and served as controls for the etiolation treatments . Compared to controls, wrapping etiolated stems improved rooting of M .26 (60% vs. 82%) and 'Ottawa 3' (81% vs. 97%) apple and of 'Britannia ' (76% vs. 90%) and 'Unknown Warrior' (80% vs. 91%) rhododendron. Etio lation improved rooting percentage of 'Unknown Warrior' regardless of wrapping. Regardless of etiolation, forcing 'Ottawa 3' at 18 degrees C improved rooting percentage (92% vs. 74%)and roots per cutting (12 vs . 7) compared to forcing at 28 degrees C. Etiolated mountain laurel cu ttings generally rooted best at 18 degrees C; control cuttings rooted best at 28 degrees C.