One of the most asked questions I get is, “Why are my houseplant’s leaves turning yellow?”. There are many reasons why this could happen. We need to narrow it down to the type of plant and the environment it is growing in. 

Yellow Plants

Many plants are naturally yellow plants or their new leaves may emerge a bright yellow and fade to a light green. This philodendron below is a good example of that. 

Older Leaves

As I tell people in my presentations, everything is aging. We are aging and so are our plants. If the yellow leaf is an older leaf, meaning it is near the base of the plant, it is natural for it to turn yellow and fall off. The primulina below has an older leaf that no longer contributes to the photosynthesis of the plant. Remove the yellow leaf. Whereas in nature, it would  fall off and decompose, we don’t want that to happen in our homes. Decomposing leaves can cause problems in our potting medium and for our plants. So remove them and discard or compost the dead leaves. Many gesneriads form long necks as they age and the bottom leaves fall off.  Read about another gesneriad that gets a long neck here and how to solve that problem.

Inconsistent Watering Practices

The most common reason plants have yellow leaves is inconsistent watering. I know that is the problem here at my house. I allow my plants to get too dry because some days I don’t have time to water. They dry out, get watered and perk back up. The consequences of that inconsistency is yellowing leaves, as in the ‘Cebu Blue’ pothos below. Because it has been in a basket for awhile, it needs some nurtrients so I will be fertilizing. If you plant is a bit off color, it may be that it is in need nutrients. Fertilize consitently to prevent that.

The same can be said for the oxalis, ficus, and scindapsus below. 

Too Wet or Too Dry?

Inconsistent watering means your plant dries out too much. Strive to NEVER let any plant COMPLETELY dry out. The only plant that doesn’t mind that is a cacti or other succulent. Yet, even those plants would do better not allowed to become “bone dry.” Leaves become yellow if the plant is too wet, but that will involve many leaves. This will also happen if the plant is too dry.

How can you tell the difference?

Feel the potting medium-is it wet or dry? Or lift the plant-is it heavy or light? You can tell by the dying leaves. Is it turning crispy like the underwatered spider plant below or turning mushy? If it is crispy, it was too dry. If the leaf turns mushy, it was too wet for a long period of time. This isn’t always true, but are good indicators of whether your plant is too dry or too wet.

I’m not sure if this is an older spray of needles or if I’ve allowed my asparagus fern to dry down too much. It seems it drops its needles often.

Root Problems

Often it is a guessing game and you have to do what you can. If it continues, always check the soil as it may be root bound or have soil mealybugs. That will affect the plant as well, and it isn’t always clear. The plant below is definitely rootbound, the yellow leaves being the indicator. Plus it drank the water so fast, that I couldn’t keep it moist. 

Temperature

Temperature affects your plants, as well. This is especially true of cyclamen. They want to be cool when they are flowering and the leaves will yellow and collapse if they are too warm. The plant will go into dormancy. There are other plants that warm and cool temperatures will affect their leaves, as well.  

Insects and Mites

Then there is the dreaded insect or mite problem that will turn your plant’s leaves yellow. Below left is an aralia affected by spider mites. I have sprayed and tried to keep it consistently moist, so I’m slowly getting them under control, but the consequence is dead, crispy leaves (remember, spider mites love dry plants!). The plant on the right is a Dracaena ‘Kiwi’ battling mealybugs. After taking this picture, I see they aren’t under control like I thought they were. (I HATE mealybugs.) Can you see them where the leaves meet the stem? A big cottony mess! 

This leaf below has major spider mite damage. The green is gone because they have sucked all the juice out of the leaf cells. These leaves will yellow and fall off. 

Conclusion

Inspect your plants if they have yellowing leaves. Decide whether it’s a normal aging process. Is it too wet or dry, or some sort of pest has moved in? The key is to pay attention to your plants and give them the care they need. Then the only leaves that will be turning yellow is old leaves. “Do as I say, not as I do” as the old saying goes!

Have a great week, plant friends!