Yellowing leaves is one of the great mysteries of indoor plant care but it is also one of the most common. Houseplant leaves can turn yellow due to watering issues, salinity issues, and climate issues. They can also turn yellow when suffering from insect or fungal infestations. Follow below to learn more about why your plants are turning yellow as well as ways to reverse the problem.
Why Your Plants Are Turning Yellow
According to agricultural resources company IFA, “watering issues are the most common cause of yellowing leaves.” Signs of over watering include “brownish-yellow [leaves] that have begun to wilt.” IFA notes that they will “look limp or have a mushy feel” and that “black spots and lumps may appear on stems and leaves.” Overwatered plants become sluggish, producing fewer leaves and pushing oxygen out of the soil. This can lead to what IFA refers to as “under aired” roots. Under-aired roots eventually suffocate and begin to rot. Overwatering can also lead to a number of fungal diseases in your houseplants.
Conversely, yellow leaves that have begun to curl are usually due to dry soil. If you water your plant, the issue should resolve over a few days to a week. The Sill recommends repotting your plant in this case and watering it less over time to stop killing your houseplant.
According to The Sill, if the whole plant is yellow and the leaves are still hanging on, the problem is likely due to temperature. They state that if your leaves are “a more pale or whitish yellow,” the room is probably too cold or too hot. According to Nikki Tilley of Gardening Know How, heat stress can lead to yellowing or dropping leaves. Wilting may also occur when a plant has become burdened by oppressive heat. Because the plant must conserve water in these situations, you might notice that yellowing houseplants will “shed some of their foliage.” Tilley explains that leaving this issue unchecked will lead the plant to “eventually dry up, turning a crunchy brown before dying.” Try resolving the temperature issue before changing up your plant's care regimen.
Salinity in the soil and water
According to a brief released by the International Maize and Wheat Improvement Center, salinity frequently causes yellowing in plants. You might notice wilting or dull leaves even if the soil is moist and the soil’s nutrient level seems appropriate. The CIMMYT explains in their brief that “plants suffering from salt stress can be stunted" initially. They may also have leaves that are dark blue-green in color” when the issue first begins to affect the plant. However, as “salt toxicity [becomes] severe, the tissue along the leaf margins may become yellow and die.” Salt toxicity is perhaps the most complex and insidious reason houseplant leaves yellow, as it can be difficult to diagnose.
Salt naturally occurs in all soils and is important in low levels for plant health. Unfortunately, the CIMMYT explains, too much salt “can destroy soil structure.” This destruction of soil structure can cause “swelling of clays and dispersion of fine particles'' throughout the soil. This can lead to clogged pores, meaning that oxygen and water are unable to pass through to the plant’s roots. Even worse, high salt concentration in soil can cause a crust formation that prevents the plant’s roots from receiving nutrients. A crust formation can also prevent the plant from properly expelling toxins.
How To Diagnose High Salinity
This high-salt issue may have occurred early in your plant’s life, an article in the Antelope Valley Press explains. Unfortunately, you may have added too much fertilizer to your plant’s pot early on, leading “younger leaves to yellow.” Thankfully, there are ways to diagnose your plant at home. One way to diagnose your plant with a salinity issue is to measure the soil’s pH. According to the WateReuse Foundation, you might also be able to diagnose the issue by visually examining the leaves closely. The Foundation’s “Salinity Management Guide” notes that “abnormal yellowing of the leaves (also known as chlorosis) and necrosis” could both be signs.
How to Cure High Salinity
Solving houseplant soil salinity is difficult and time-consuming, explains Julie Bawden-Davis of HealthyHouseplants.com. In her article “Could Your Houseplant Be Suffering from High-Salinity in the Soil?” Bawden-Davis offers a treatment plan. Bawden-Davis recommends rinsing the plant soil - also called “leaching.” Leaching involves “running water through the soil” in amounts “three times the size of the plant pot.” Bawden-Davis explains that “slowly filtering water through the soil...will help rinse out excess salt buildup.” You can also “remove the soil that contains salt buildup” - typically the top layer of soil - and replace it with “fresh organic potting soil.” Lastly, you can fully re-pot your houseplant. Bawden-Davis recommends “shaking off the soil and rinsing the roots” before placing in a new pot with new soil. If you want to use the same pot, Bawden-Davis notes you must first “wash it thoroughly, scrubbing off any salt buildup.”
If you want to avoid yellowing leaves all-together, consider turning to Respira for your next houseplants. Respira’s living wall biofilter system is designed to flourish indoors and comes equipped with everything you will need. The only maintenance required for our unit is refilling the nutrients every three months and refilling the water basin every ten days or so.