Q.corn plants have yellow leaves with brown spots
I have 2 corn plants in 2 different pots. I planted them 2 years ago. They were healthy until now. Recently (2-3 months ago) both of them developed (are still developing) yellow leaves with brown spots. I do not know what is wrong with them and how to correct it. Thanks for your help.
Certified GKH Gardening Expert
It sounds like it could also be a fungus. If you treat the plants with a fungicide, this should help clear it up.
The most likely problem people will have with corn plants is that they overwater them. If you've had yours for almost 2 years with no problem, it is probably a small amount of over-water, over a long period of time. Corn plants kept indoors require that the soil dry almost entirely, all the way to the bottom of the pot, between waterings. If you've never checked the soil moisture down there where the roots are, you may surprised at how damp it is. This article will tell you more about checking soil moisture: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-moisture-in-plants.htm
The best thing you could do would be to repot, which will enable you to cut off rotted roots, wash out old, infected soil, and put in new, good-draining mix. https://www.gardeningknowhow.com/plant-problems/disease/treating-root-rot-gardening-tips-for-housplants.htm
If you can't do that, get the plant into higher light, and set up a small fan to blow over the soil.
Another aspect to consider is possible over-fertilization. If you've fertilized frequently (I don't recommend fertilizing corn plant more than 3 or 4 times a year,max,) you may have a salt build-up in the soil. Running a quantity of water through the soil (5X's the volume of soil) will take care of that, but then of course you have serious problems with drying out afterward. Repotting, being sure to wash off most of the old soil, will also work.