Nutrient leaching (and its prevention)
I've been tending three exotic potted plants for about two years: an olive tree, a lime tree, and a kumquat tree. These plants sort of fell into my lap when I visited a yard sale in my neighborhood, and happened to have use of a pickup truck to take them home for very little money. (I think they were $15 ea., for trees over 3' tall.)
They live on my concrete-slab patio during the warm seasons, and behind a west-facing bay window during the winter. During the first winter, the citrus bore a delightful amount of fragrant blossoms and fruit, but lost many leaves as spring approached. "I guess I should have been more careful about watering them", I thought. During the summer, they got lots of rain, and hand-watering as needed, and they all put out fresh leaves, but just a few fruit. "I guess they're waiting for winter again", I thought. But I didn't get fruit last winter, and not only did they shed some leaves (though not as many), whole branches withered and died. "Maybe I'm giving them too much water this winter", I thought. Back on the deck this recent spring, they did not revive as before.
Then, I realized that the heavy summer rains of 2019 had probably leached a lot of nutrients out of them. Supporting evidence: algae was growing on the patio, using the lost nutrients. I hastily applied a few tablespoons of "citrus fertilizer" to each pot, and saw amazing responses from each within two weeks. Leaves, shoots, and then blossoms appeared.
Now, how could I prevent losing these nutrients again? I don't want to waste fertilizer, whether it's something that I buy or something that comes from the compost pile. What I've done is to salvage some corrugated plastic panels (formerly political campaign signs), cut them into disks that (mostly) cover the tops of the pots, and split sections of PVC pipe to protect the trunks. A locking cable-tie holds the two halves of the split pipe together, and also prevents the disk from lifting in the wind.