In my gardening life I have raised bumper crops of many things, including roses, tomatoes, zucchini, mint, and larkspur. My biggest success, though, has been with plastic plant pots. I get new ones every year, ranging in size from tiny to multigallon capacity, from nurseries, garden centers, and mail-order vendors.
The pots are plastic and I am thrifty, so I don't just throw them away. I use them to pot seedlings or transplant older specimens. When I run out of plants, I store pencils, small garden implements, and plant tags in the baby ones and larger equipment in the bigger ones. Damaged pots and cell packs get cut up and parked in the bottoms of larger pots to provide drainage. Despite my constant and heroic efforts, I still have more plastic pots than I need – stacks of them, in fact.
I was spending the usual half-hour cutting up some used cell packs one day, when I finally figured out the answer. Plastic plant pots are just like paper clips and wire coat hangers – they give birth in the murky hours between dusk and dawn. I don't know whether they divide like amoebas or reproduce by some complicated extrusion method. It's possible that they even regenerate from those cutup pieces in the bottoms of the bigger containers. I don't know because I haven't stayed up late enough to see it happen.
The only thing I know for sure is that plastic pots are the most prolific garden containers. High-end terra cotta pots don't appear able to reproduce without human intervention. It's obviously the same with marble, zinc, wrought iron, and concrete planting containers, all of which have long since achieved zero population growth. This is probably why they command such high prices at garden antique shows and shops in the pricier neighborhoods.
Last year I solved one of contemporary gardening's major mysteries, unraveling the mechanism by which mulch disappears from beds and borders. With that feat of detection under my belt, you would think I could also divine the mysteries of plant-pot reproduction. My reference books are useless on this subject, mostly because I am a reference book snob and don't own any volumes published since the advent of modern plastics.
I am not opposed to information technology, however, so I did a comprehensive Internet search. I checked every reference, went to the prestigious Royal Horticultural Society website and accessed all kinds of scholarly and arcane Web pages. There was nothing. Plastic plant pots may be common, but their ways are inscrutable and they keep their secrets to themselves.