The purpose of this study was to (1) determine whether the probiotic bacteria Lactobacillus fermentum InaCC B1295 were able to adapt (compatible) to mustard greens (Brassica junceae L.). (2) Knowing the effect of the probiotic bacteria Lactobacillus fermentum InaCC B1295 on the growth of mustard greens (3) Obtain the best concentration for the growth of mustard greens. This was an experimental study and used a completely randomized design (CRD) with 4 treatments and 4 replications to obtain 16 experimental units. The data were analysed using SPSS version 9.1.3 and ANOVA, then followed by Duncan's New Multiple Range Test (DNMRT) at 5% level. The results showed that the application of the probiotic Lactobacillus fermentum InaCC B1295 was significantly different from the control. So it can be concluded that the probiotic bacteria Lactobacillus fermentum InaCC B1295 are able to adapt their life (compatible) to mustard plants, and have a positive effect on the growth of mustard greens. The 105 CFU/mL dilution is a good treatment to stimulate the growth of mustard plants.