I restrict myself these days to Zygocactus and Pothos. Occasional gifted houseplants and the annual poinsettias are held prisoner and then offered as sacrificial lambs to the houseplant gods to curry their favor in the direction of my Christmas cacti. In place of the ceremonial altar and a flint knife, I have substituted benign neglect and the arid, desert-like humidity of the natural Kansas environment, watering only when I see signs of wilt.
That practice has not been kind to the mandarin orange and lemon tree that Mrs. ProfessorRoush insisted I add to our floral menagerie. Both trees spend their summers outdoors on the porch, where it is moderately humid and I frequently forget to water them. They spend their winters indoors where the humidity is very low and I frequently forget to water them.
Recently, I noticed that my fairly spindly orange tree was wilting at the top (above). "Wait a minute," I thought, "orange leaves don't wilt; they yellow and fall off." And indeed, on a closer look, I recognized there was a second stem in the pot; a spindly sun-starved basil that presumably was an offspring from one of our herbs, which also spend summers in pots on the back porch. You can see the second stem better here at the left.
I'm certainly not going to root up this volunteer. If a weed is just a plant in the wrong place, this "weed" is in the right place. Mrs. Basil has done me a favor by going to seed and placing an offspring here in this pot to be nurtured. The rest of the winter, I think I'll just watch the basil as an indicator for watering this pot and the lemon tree next to it. Maybe both trees will now have a better chance to live to see another spring. Besides, the basil smells so good.