Postharvest Handling Techniques for Long-term Storage of Cut Tulip and Dutch Iris

Abstract

Postharvest handling is a multifaceted stage of the cut flower supply chain intended to maintain or improve the quality of perishable cut flower material. During this stage, cold storage is used to maintain quality and extend availability. Three experiments were conducted over the course of 2 years using cut tulip (Tulipa hybrids) and dutch iris (Iris ×hollandica) cultivars to evaluate the impacts of dry storage with the bulb attached to the stem, sub-zero temperatures, and pre-storage and post-storage floral pulses on vase life. In the first experiment, six tulip and two dutch iris cultivars were stored for up to 6 or 8 weeks, respectively. The longest vase life at 6 weeks of storage was achieved for all tulip cultivars when stems were stored with the bulb still attached at-0.6∘C. Storing cut stems at 0.7∘Cfor6weeksresultedintheshortest vase life. The vase life of ‘Telstar’ and ‘River King’ dutch iris was longest at 4 and 2 weeks of storage, respectively, when stored at-0.6∘C with the bulb attached. Additionally, 75% to 100% of flowers fully opened when stems were stored with the bulb still attached and 42% of flowers were able to at least partially open. In the second experiment, cut stored tulip stems maintained a vase life similar to that of nonstored, pulsed stems at 6 weeks of storage when pulsed with floral solutions containing benzyladenine and gibberellic acid phytohormones for 8 hours before storage. Similarly, dutch iris maintained significantly longer vase life and were able to fully expand flowers more often (60% to 80%) when prepulsed with the floral solutions compared with stems prepulsed with tap water after 6 weeks of storage at-0.6∘C. Extending the length of pulsing time from 8 hours to 24 hours was not a significant factor in vase life and post-storage evaluations of flower opening. However, dutch iris flowers with an emerged secondary bud maintained an extended vase life up to 5 days post-storage. In the final experiment, the longest tulip vase life was achieved by combining a sub-zero storage temperature of-0.6∘C, storing stems with the bulb attached, and pulsing stems with floral solutions after storage. Vase life did not significantly decrease over the course of the 6-week storage duration. Dutch iris stems pulsed with floral solutions after sub-zero storage with the bulb attached were able to more fully open after 8 weeks of storage compared to stems held dry or pulsed with tap water. These three experiments over the course of 2 growing years demonstrate various strategies for successfully storing cut tulips and dutch iris for an unprecedented duration while still maintaining vase life.