This experiment was undertaken to determine tulip adaptation to mild winter areas of Argentina and to define the best production period. Two hybrids, Ile de France (for potting systems), and Yokohama (for cut flower or bed systems) were evaluated in 2004 at San Pedro, Buenos Aires province. Bulbs were planted on six dates at weekly intervals between June 23rd and July 28th. The vegetative (PV) and flowering (F) periods, plant height at the beginning of F, and stem length at the end of the cycle were recorded. These records were regressed on temperature variables. Air temperature ranged from 13 to 18°C. For Ile de France, delaying the planting date caused a shortening of PV (43 to 30 days) and F (23 to 16 days), and an increase in stem length at the end of the cycle (46 to 54 cm). Mean air temperature during the PV and F explained 73% of the variability in cycle length and only 21% of that of stem length. For Yokohama, delaying the planting date caused a shortening of PV (49 to 32 days) and F (25 to 18 days), and an increase in stem length at the end of the cycle (35 to 42 cm). Mean air temperature during the PV and F explained 61% of the variability in cycle length and 33% of that of stem length. We conclude that both hybrids will produce good flower quality when planted between June 23rd and July 28th.