Experts and BHG readers answer.
stems of petunia's turning brown next to the dirt, still putting out blooms
Thanks for writing. Is it just the stems you're noticing starting to turn brown or are the leaves at the base of the plant dying, too? If the plants are somewhat bushy, it may be that the stems and leaves at the base of the plants aren't getting enough light. Or it could be old age -- the first leaves are getting old and naturally dropping and the stems are getting thicker and more mature. It's actually pretty common for older varieties of petunia to get a ""bald spot"" at the center of the plant. (Newer varieties such as Potunias, Ramblin petunias, and Wave petunias don't tend to do this.)
---Justin, Senior Garden Editor, BHG.com