Assessing growth variation among M. truncatula accessions under simulated autumn conditions (SAC) is important to characterize the potential of the crop as a winter annual and as a model plant for alfalfa improvement. Although M. truncatula has been widely used for various genetic studies, little is known about the genetic variation in growth among its accessions. We measured dry matter accumulation in root and shoots of thirty-five M. truncatula accessions and five alfalfa fall dormancy checks. Seedlings were grown in the greenhouse for 4 weeks and then transferred to growth chambers under SAC constant conditions. Root dry weight (RDW), shoot dry weight (SDW), stem length (SL) were recorded before and after the treatment period and the first flowering date of the genotypes were recorded. Differences in RDW, SDW, TDW, SL and the first flowering time were observed among the M. truncatula accessions and between M. truncatula and M. sativa under the both conditions. Dry weights of M. truncatula accessions were higher under SAC but SL was higher under constant conditions. Accessions under constant conditions (25°C and 400 µmol m^-2 s^-1 PPFD) flowered earlier than the variable temperature. Accessions originated from Africa flowered earlier than the European but they did not differ for other growth parameters. M. truncatula and M. sativa differed for all the measured growth parameters. Overall, the results indicated that there is an exploitable variation in flowering time and biomass production among M. truncatula accessions. Higher biomass observed under SAC may indicate the potential cold tolerance in the species, which will be further investigated with a sub-set of these accessions.