Why are my calamondin's leaves yellowing?
I bought my calamondin plant at Homestead Gardens in May. I placed it on my porch which gets full sun. I used Earthgro potting soil mixed with soil in my garden, which tends to be sandy. I first spotted the yellow leaves in July, and while there were still green leaves, they were no longer waxy and dark green. In August, most of the leaves turned yellow and had started to curl inward, like it was folding itself in half. I put in a Jobe's Organic Fertilizer Spike formulated for potted citrus trees and watered the plant two to three times a week. It seemed to stop curling and it made it bloom again, but it still is yellow. The fruit is also not as big as I've seen it with other plants, and it also seems to be dying earlier.
Anne Arundel County Maryland
We don't often get a lot of questions about potted citrus.
The yellowing, sickly leaves could indicate a couple of things.
Have you checked carefully beneath the leaves? Mites and scale insects are not uncommon. Use a hand lense or magnifier if you have it to look for tiny spots, which could be spider mites. Bend a branch over a sheet of white paper and shake/bang it swiftly and see if anything dislodges and walks across the paper.
Both spider mites and scale are sucking insects which can cause leaf 'stippling' which can coalesce into yellowing.
Over watering or underwatering can cause yellowing as well. Take a look at the link below for best care. You want the top inch of the soil to dry out between waterings, and in the winter, when they will 'rest' a bit, water only enough to keep the soil mixture from completely drying out.
We also wonder about sunscald. These plants need at least 4 hours a day of direct sunlight to do their best, and need the brightest light you can give them, but maybe not all day sun, especially in the late afternoon.
If the yellowed leaves are caused by damage, insect, sun or otherwise (as opposed to nutritional), those particular leaves are not going to regain their green, healthy appearance.