Precooling, Planting Depth, and Shade Affect Cut Flower Quality and Perennialization of Field-grown Spring Bulbs

Abstract

Narcissus L. `Music Hall', N. `Tahiti', Tulipa L. `Couleur Cardinal', and T. `White Emperor' bulbs were precooled at 5 °C for 0 or 5 weeks and planted 15, 30, or 45 cm deep (from bulb base) into raised ground beds under 0%, 30%, or 60% shade. Plant growth was monitored for two consecutive years after planting. Precooling reduced the percentage of T. `White Emperor' that flowered but did not affect flowering percentage of the other cultivars. Precooling delayed anthesis in one or both years for all cultivars. The greatest percentage of bulbs flowered when planted 15 cm deep and the 45-cm planting depth reduced flowering percentage. Increasing planting depth delayed anthesis for all cultivars. Increasing shade increased stem lengths in one or both years for all cultivars, but did not influence flowering percentage. Perennialization was low for all cultivars regardless of treatment. Cultivar differences in perennialization occurred; in year 2 up to 30% of N. `Tahiti' bulbs flowered vs. 32% for `Music Hall' and up to 30% of T. `White Emperor' bulbs flowered vs. only 22% of `Couleur Cardinal'.