INTERACTION OF BULB VERNALIZATION AND SHOOT PHOTOPERIOD ON NELLIE-WHITE EASTER LILY

Easter lily (Lilium longiflorum Thunb. 'Nellie White') bulbs were expo sed to 1, 2,3,4,5, or 6 weeks of cold before shoot emergence; 0, 1, 2, 3,4,5, or 6 weeks of long days (LD) upon shoot emergence; or a combina tion of cold followed by LD: 115 (weeks cold/weeks LD), 2/4,3/3,4/2, o r 511. Experiments were repeated for three consecutive years. LD did n ot substitute equally for cold-, at least 3 weeks of cold were require d before LD treatments resulted in anthesis. Depending on the year, 10 0% of the plants flowered when treated with 3 to 6 weeks of cold alone or in combination with LD. Days to first flower anthesis from plantin g increased with decreasing weeks of cold in years 1 and 3, but was si milar for all treatments in year 2. Decreasing weeks of cold in combin ation with LD, however, decreased days to anthesis in years 1 and 2, b ut had no effect in year 3. Regardless of LD, days from emergence to v isible bud increased with decreasing weeks of cold in all years, and d ays to emergence from placement in the greenhouse increased with decre asing cold in years 1 and 3, but not in year 2. Increasing weeks of co ld, regardless of LD, decreased leaf count, but had no effect on plant height. Flower count was unaffected by cold when combined with LD, bu t was significantly reduced by increasing weeks of cold.