What causes tulips to bloom short?
Length of tulip stems at harvest is related to two aspects of temperature: number of cold weeks before flowering and temperature during the last stage before flowering, when flower buds are visible. When tulip bulbs are planted in the fall, they should already have completely differentiated flower parts. So in the case of tulips, the dormancy-breaking cold weeks are not necessary to induce the flower to form; it is already present in the bulb. However, a requisite amount of time at cold temperatures (which varies by cultivar) is required for flower stem elongation. During these cold weeks, a growth hormone called gibberellic acid (GA) is translocated to the growing point of the bulb, and this contributes to the development of the long stems that we desire in cut tulips. If cold weeks are short, the naturally-produced GA is not present in sufficient quantities to lengthen stems before the flower opens. The second aspect of temperature that can dramatically influence the length of cut tu
