The options to optimize the production of plants and the lifespan and phenological characteristics of Mimulus guttatus DC in the climate of Sofia were studied. The seedlings were grown in a greenhouse for 8-10 weeks, at a temperature of 12-17ºC, intensity of natural light – 1300-18500 lx and air humidity 63-74%. The young plants had the following biometric characteristics: a rosette structure, 5 pairs of leaves with length of 7.60 ± 1.37 and 8.11 ± 1.61 cm for the first and second pairs of leaves and respectively average width of 2.39 ± 0.54 and 2.66 ± 0.70; average height of the stem: 16.06 ± 3.6 cm. A link between the amount of precipitation during the growing season in the field and the morphology and lifespan of the individuals was sought, with a view of assessing the risk of self-sowing of Mimulus guttatus potential performance as invasive species in the park areas of the city. With precipitation over and around the normal for Sofia, on a soil substrate with unfavourable structure and low availability of nitrogen and potassium and average availability of phosphorus, two experimental options were tested: with none and with a one-time fertilization. Mimulus guttatus plants bloomed around 1.5 months and performed as annuals, with no evidence of self-sowing or overwintering, with no danger of invasion or threat of uncontrolled proliferation.