Effects of heat treatment and chilling duration on camas growth and development

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Great camas (Camassia leichtlinii (Baker) S. Watson [Asparagaceae]) and common camas (C. quamash (Pursh) Greene) are two of the most culturally and ecologically significant native geophyte species in the US Pacific Northwest. Like many geophytes, seasonal thermoperiodicity affects their growth and development. The daughter bulb of great camas grows and develops during the summer rest period. Increasing the duration of the summer rest period results in longer leaves in the subsequent growing season. Great camas, common camas, and meadow death camas (Toxicoscordion venenosum (S. Watson) Rydb. [Melanthiaceae]) require a period of chilling during their winter rest period to induce leaf emergence, and as the duration of chilling increases (1) the odds of leaf emergence increases, (2) the period between the cessation of chilling and leaf emergence decreases, and (3) leaf growth in the first week after leaf emergence increases. These results inform growers as to the proper storage methods for these species during their rest periods. Additionally, the chilling optimum, here defined as the amount of chilling at 4.6 °C that minimizes the duration of the winter rest period, is approximately 80 days for both great camas and common camas. However, this optimum was determined without considering a potential interaction with the heat treatment. Knowing the optimum duration of heat treatment and chilling may allow growers to manipulate native bulb species into emerging for multiple growing cycles in a single year, which could expedite their production.