I have wondered this often too. The two plants don't even flatter each other when planted in a pot.
I have 2 hardy geraniums that have been returning in spring for almost 40 years. When I find a little seedling volunteering I have been potting them up in great soil and babying them all summer, putting all in the dirt before October first. These plants are so much stronger, larger and have more flowers than seedlings left to grow where they land.
