Much of the variability of appearance which different bush mimulus may show is due to cultural variations in the way they are grown. Although it may be said that bush mimulus are sun loving, they also do very well in the shade. The same plant (or a cutting of it) may respond quite differently depending upon the amount of sun and shade it receives. Generally, at least partial sun is needed. Bush mimulus grown in deep shade will generally bloom much less, or not at all, compared to those grown in the sun. On the other hand, too much sun and heat can burn out the plants, which will grow and bloom quickly and then become exhausted in early summer. I have found some species can tolerate full sun better than others.
I have noticed that very young plants, which have not bloomed, grown either from seedlings or cuttings, remain deeply green throughout the summer, and do not go dormant. Larger and older plants, often go somewhat dormant during the summer after they have bloomed. Sometimes young plants will come into bloom comparitively late in the summer, and in this way it may be possible to prolong the flowering in the garden.
Each year, some of my plants die out, but almost always this happens during the middle of their bloom, or more likely after they have gone dormant for the summer. Again, young plants which are too young to bloom, or plants in deep shade which do not bloom, generally neither go dorman nor die out. Some species seem to be more inclined to go dormant or die out than other species.
Bush mimulus plants grown in partial shade, and with ample moisture, may remain in full bloom, green, and attractive, for a considerably longer time than those grown in full sun. Plants in pots probably will not perform as well, nor bloom as long, as similar plants which are in the ground.
For many bush mimulus species and hybrids, blooming occurs on older folliage. The age of the folliage tends to be transmitted into cuttings. That means that plants grown from cuttings from an older branch may bloom in the first year. But plants of the same line grown from seed often take longer to bloom. On the other hand, plants grown from seed tend to be bushier, especially at the base of the plant, than those grown from cuttings.
[updated 7/22/2000]