The growth and flowering of Hymenocallis × festalis

Bulbs of Hymenocallis (including Ismene) have showy, fragrant flowers. Little is known of the horticultural potential of these plants, and observations and trials on a stock of Hymenocallis × festalis are described.

In a stock of glasshouse-raised bulbs, bulb grade exerted a marked effect of the number of florets produced, which increased from 2 in 9–10-cm-circumference bulbs, to 7 in 18–19-cm-grade bulbs. Field-raised bulbs of the same grades produced fewer florets. Bulbs were usually planted for flower production in the glasshouse in April; earlier planting (February) leading to greater floret size but a longer period in the glasshouse before anthesis. Planting could be delayed at least until June, or later flowering could be achieved by storing the dry bulbs over winter at a low temperature (5°C), but the latter treatment reduced the percentage of bulbs which flowered. The long scapes could be dwarfed by ethephon (as Ethrel). Hot-water treatment, as a pest and disease control measure, did not result in damage to the flowers provided it was delayed until after the staminal cup initial had been formed.

In the field, growth of the main bulb was more vigorous than in the glasshouse, but pot culture in the glasshouse led to copious offset production. Data are presented for bulb increases for various grades of bulbs planted in outdoor beds at rates of 350–1050 g per metre row.