Horticulture in Colorado is diverse from the standpoint of types of plants grown and even more so in terms of climate. Topographic elevation ranges from slightly over 3000 feet in the eastern high plains to over 14,000 feet in the Rocky Mountains (50 peaks exceed this elevation!). The frost-free growing season varies from 16 days in certain high mountain valleys to 192 days in the fruit growing areas in western Colorado. However, a common factor in all areas, regardless of altitude, is the need for irrigation water — Colorado is a semi-arid state in which precipitation varies from less than 8 to slightly over 16 inches.
Tubers of three potato cultivars (Norland, Desiree, and Russet Burbank) produced on field-grown plants, greenhouse plants (minitubers), and in-vitro plantlets (microtubers) were kept at 5, 10, and 20°C. Sprouting was recorded throughout a 14- to 22-week storage period. The effect of cultivar, temperature, and tuber size closely followed previous research for field- and greenhouse-produced tubers. For in-vitro produced microtubers, the temperature effect followed an expected pattern, but the cultivar effect was different from that observed for field and greenhouse tubers. Two sprouting indices were developed (sprouting rate index and sprouting ratio index) to quantitatively describe the sprouting characteristics. Correlation coefficients suggest that the “sprouting ratio” method can be an acceptable alternative to the “sprouting rate” method.