The success of some plant species comes from the simple fact that they can grow where other plants can't. Such is the case for the purple mouse ear (Mimulus/Diplacus douglasii). Native to northern California and Oregon, this tiny plant can most often be found growing in serpentine soils. Finding it can get tricky as it is quite diminutive in size and doesn't always produce its outlandishly showy flowers.
Mature plants stand roughly 4 cm in height. When produced, the flowers are rather large and showy, often much larger than the rest of the plant. Unlike other members of the genus, the bottom lip of the tubular flowers has been reduced so much that it might as well not exist. Instead, the two top petals dominate the display, giving this plant a cartoonish outline of a mouse. As you can see, they are incredibly showy.
This plant has to do what it can to ensure that it sets seed in any given growing season. Purple mouse ears are annual plants, so they only get one shot at reproduction. To make matters more difficult, they frequently grow in serpentine soils, which are low in essential nutrients and high in toxic metals like nickel, cobalt, and chromium. Despite these difficult conditions, purple mouse ears seem to benefit from the lack of competition on these traditionally toxic substrates.
Plants don't always produce their showy floral displays. When times are tough, they opt for asexual reproduction. Instead of the big, showy flowers, plants will produce tiny flower buds that never open. These are called cleistogamous flowers. Instead, they simply self-pollinate, which ensures that the genes that allowed the parent to survive environmental hardships are guaranteed to make it into the next generation. For annuals whose entire life is wrapped up in a single season, sometimes its not worth taking any chances.
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