Cold soil: a signal from below

Thinking about plant senescence as we turn the corner into fall. I realize it's not just sunlight that affects growth processes in plants. It's also soil temperature. 

Getting ready for the big move in in October, I've started emptying the pots with hot weather plants like coleus. The plants lost most of their color and a lot of their leaves over the past few weeks and the purple spikes of flowers have long gone to seed. As I turn the pots over I realize the soil is cold, even in the afternoon. 

Well it makes sense. Cold nights in the 40s and daytime highs that just reach 60 make for cold soil. A message to the plant roots that encourages slowing down. Some of the soil goes on top of the compost heap in back, now a mass of vegetable peelings, corn husks, and old corn cobs. That soil will introduce microorganisms to break down the remains, almost as if the black soil self regenerated. 

Some of the soil, the cleanest, will go into the soil container, to be re-mixed and used next spring for the new potted annuals. 

And some of the soil, the stuff I can't easily separate from tightly packed roots or stubborn stems, I'll throw back into the garden, whose surface seems to sink an inch or two every year. 

Cold soil in the pots reminds us that we're entering a time where everything, not just the house and not just the air, is readjusting for a new season.