The geranium was chosen to be associated with St. Teresa of Calcutta for several reasons: it is sturdy and beautiful, it is simple and pervasive, and it is unassuming but even in hard environments it can thrive.
The semblance of the flower in line with Mother Teresa is obvious-- this little woman, so firm in mind, so tenacious in spirit, and (even in the hardest times) she was able to flourish in her faith enough that anyone who beheld her was inspired by her straight-forward love