Personally..I wouldn't go "liming-up" my soil without doing a soil test...if you top dress your gardens with organic matter such as composted cowmanure and compost..that will keep your plants and all the worms happy and productive..I am not a big fan of preen..you might be killing seeds from last years flowers that won't germinate #1 and what is that stuff doing to the worms??..Pentas are so easily to grow they love full sun and honestly ..they may be getting too much water ..is why the leaves are yellowing and who know's if you got preen on the leaves..that isn't helping either..I do nothing to mine..they come back each year from the roots and bloom like mad..they love the sun and heat....Jeanne

Oh, Jeanne, how I envy your being able to leave yours in the ground and have them come back. They are very definitely an annual for us in North Texas. At least, for me, as I have never had one come back. But they are beautiful, and I have to have a few each year. I tried carrying them through in the plant room one year, but they did not care for the humidity in there, so I won't bother myself with that again.