Growth and Yield of Safflower in Three Temperature Regimes 1

A better understanding of the response of safflower ( Carthamus tinctorius L.) to elevation, temperature, and date of planting is needed to best exploit this crop in regions of its present adaptation. The objectives of this study were to describe the response of growth characteristics to date of planting when grown in irrigated desert environments that varied in elevation and, therefore, in temperature. Growth characteristics measured during early plant development were days to emergence, days in rosette, and days to flower. For later growth, numbers of branches and heads per plant, seeds per head, seed weight, seed yield, oil percentage of seed, and oil yield were recorded. Early plantings (November 15 to December 15) in areas of higher elevations provide for lower temperature regimes during growth. The rosette period is lengthened and increased yield of seed and oil occur from increases in head numbers and seeds per head. For November 15 plantings in warm areas of low elevations, temperatures are generally not low enough during early growth for normal plant development and seed production. Later plantings (December 15 to January 15) are recommended for these temperature regimes, however, yield will not be as high as those from colder regimes. Heat‐tolerant germplasm is needed to improve yield of seed and oil percentage of seed for the warmer desert areas of the Southwest.