Cast Iron Plants have become synonymous with the everyday houseplant, and for a good reason. Not only are they beautiful, but they’re also tough as nails and thrive in a wide range of conditions. Over time, they may start turning yellow, which can sometimes be a bad omen.
Your Cast Iron Plant is turning yellow because it’s getting too much or too little water or sunlight. Cast Iron Plants need just a little bit of sun and well-drained soil to thrive. You should also inspect the plant for root rot and pests. Also, avoid fertilizing the plant more than once a month.
I’ll outline why your Cast Iron Plants may turn yellow in this article. I’ll share some ways to narrow down symptoms for each so that you can identify the cause and take care of it. Finally, I’ll give solutions to the causes and share helpful tips on preventing similar stress on your plant in the future.
6 Causes of Yellowing in Cast Iron Plants
Sometimes, the cause of plant stress can be challenging to pinpoint. For new plant owners, indoor plant care can be counterintuitive at times, too. It is essential to stop, think, and review the plant’s condition before taking any action outside of the plant’s standard regimen or routine.
One of the most common responses to signs of plant stress with new plant owners is to water the plant more. There’s often this almost knee-jerk response to any sign of plant stress that it needs more water, but the problem is that often, overwatering only makes the situation worse.
I can’t stress this enough — before you take action to reverse the yellowing of your plant, stop and thoroughly evaluate the plant’s condition. It’s easy to make assumptions or want to jump into action, but please resist that urge. Only once you have thoroughly evaluated the plant should you decide how to act on the stress indicators and symptoms.
Waterlogged Soil Is Causing Stress
The most common cause of yellowing Cast Iron Plant leaves is overwatering. Cast Iron Plants are so hardy by nature that even regular watering for your typical houseplant could prove to be too much for a Cast Iron Plant.
There is no perfect answer for how frequently to water a Cast Iron Plant. Some say once every two weeks; others say once a week. And yet others say they water it when it looks wilted or when they remember.
The watering frequency will depend on your climate, the amount of light it’s getting, how often forced air runs, and more. In general, it is best to water a plant thoroughly, then allow it to dry out completely before watering it again.
By dry out completely, I mean that when you push a finger into the soil, the potting medium is dry on the surface and several inches down into the plant.
So, how to check if your Cast Iron Plant has waterlogged soil?
If you tilt the pot to one side, you’ll see the water moving around within the soil. That is a clear sign of overwatering.
Cast Iron Plants like to be watered thoroughly, but they prefer fast-draining soil, so sitting in water is not to their liking.
Another way to tell that they are waterlogged is to look at the catch tray that the pot is sitting in. If it is damp or wet, it’s a sign that the plant is being overwatered.
The Cast Iron Plant Suffers From Root Rot
Closely related to the issue of being overwatered, another cause of Cast Iron Plants turning yellow is root rot. Root rot is a natural consequence of long-term overwatering and leaving the plant in wet soil.
When a plant is overwatered long-term, the water and damp environment break down the organic materials that make up the root system. Ultimately, the water kills the root system, which means that the plant may be getting plenty of water, but it can’t absorb any nutrients because the roots have died.
When this happens, the plant looks like it’s dying of dehydration — that’s because it is. It can’t absorb any water since there is no viable root system.
You can often tell your Cast Iron Plant has root rot just by sniffing the plant or the soil at the base of the plant. Plants that are dying as a result of root rot have a distinctly coppery scent to them. For more information on this, check out my other article on houseplant smells and diagnosing the underlying issues: Why Do Your Houseplants Smell? 11 Causes and Solutions
You can also smell this scent when you pull the plant out of the pot. It’s hard to ignore when you remove the plant and the potting matter from the planter. It has a distinct scent of organic matter that’s in the process of breaking down or has already broken down.
Plant Is Getting Too Much or Is Getting Direct Light
Another reason your Cast Iron Plant could have yellow leaves is that the plant is getting too much light. Remember that these plants don’t like direct sunlight and thrive in low-light conditions.
Ideally, the plant is in an area that gets indirect light. It’s not dark, but it’s not too bright either. At no point in the day should the plant actually be in direct sunlight.
This is a tricky symptom to diagnose. You may see dark scorch marks if the plant is in direct sunlight. It’ll look as though parts of the leaves have been burnt. In a way, they have been burnt.
It can manifest differently if they’re getting too much indirect light, specifically as a yellowing leaf. The damage to the leaves often starts as brown edges and gradually turns into more yellowing. If your yellowing leaves started with brown edges, there’s a good chance the plant is getting too much sun exposure.
The Plant Isn’t Getting Enough Light
Unfortunately, yellowing leaves on a Cast Iron Plant can also be an indicator that the plant isn’t getting enough light. I know — this is getting confusing! Does the plant want more light or less light?
Consider the location of the plant and the time of year. If the plant is positioned in a dark room in the winter months, gets little to no indirect light, and is starting to turn yellow, try moving it closer to a light source.
Remember that Cast Iron Plants won’t tolerate direct sunlight. If you believe your plant is yellowing due to insufficient light, resist the urge to move it into direct sunlight. Not only will this shock the plant, but it’ll scorch the leaves.
Instead, try moving it to a brighter location gradually. Perhaps that means moving the plant halfway between where it is now and a light source. Give the plant several days to adjust and see if that changes the color of the leaves before making any additional changes.
The Plant Is Infested With Pests
This sounds worse than it is. Pest species that impact houseplants are relatively common. Have you ever seen a houseplant with tiny bugs flying around them? These are simply one of many pest species that can infest houseplants.
Anytime you bring the natural world indoors, you bring bits of nature that you may not want around indoors. It’s an expected outcome of bringing plants into your home. But this doesn’t mean you have to live with the pest species.
As annoying as they can be for you, an infestation can significantly adversely impact your Cast Iron Plant as well. As soon as you see bug activity in the soil, either around or on the plant itself, it’s time to take immediate corrective action.
First, check your Cast Iron Plant for spider mites. They’re common pests for most houseplants, but they especially thrive in dry conditions with low light. Coincidentally, these are the conditions that Cast Iron Plants thrive under as well.
The Plant Has Been Over-Fertilized
People often forget to fertilize their houseplants regularly, so this is the least common cause of yellowing in your Cast Iron Plants. However, when someone is overzealous with fertilizer, it can cause discoloration of the leaves.
Yellowing leaves are a very early and very brief sign of overfertilization. Cast Iron Plants rapidly move through the yellowing leaves stage to the scorched leave stage when there’s too much fertilizer.
One other solid indicator that the plant has been receiving too much fertilizer is that the soil can begin to look like a crust of salt or crystals forming on the surface or around the inner edges of the plant’s pot.
Solutions for Yellowing in Cast Iron Plants
Once you have narrowed down the primary cause of the yellowing in your Cast Iron Plant leaves, you must act quickly to mitigate the damage. In this section, I’ll talk about the ways to stop the damage to your plant. I’ll share the specific actions you should take to save your plant based on the primary cause of the stress.
Interestingly, some of the actions are similar for several possible causes of yellowing leaves, if not precisely the same. This is great because if you’re not entirely sure of the grounds and think it could be more than one possible stressor, you can typically take the same course of action to reverse the damage to your plant.
When reviving a stressed plant, consider the charge that physicians are given. First, do no more additional harm. This must always be the primary goal when addressing causes of stress in houseplants as well.
Dealing With Waterlogged Soil
One of the best things you can do for a Cast Iron Plant with waterlogged soil is to dry the soil out as quickly as possible. Remember that Cast Iron Plants don’t like direct or bright sunlight, so you’ll have to factor that in as you approach drying the plant and soil out.
A great way to deal with waterlogged soil is to simply repot the plant. When you do so, replace as much of the current soil as possible with a fresh batch of new, dry potting medium. This will dry the plant’s root structure out quickly and address any rot that may have been caused by overwatering.
For a full rundown on how to repot a Cast Iron Plant, check out this other article. This article shares considerations on choosing a new pot and the correct type of potting medium, in addition to directions on how to repot the plant: How to Divide a Cast Iron Plant (Complete Guide)
Corrective Action For Plants With Root Rot
If you suspect or your nose tells you that your Cast Iron Plant is experiencing root rot, you must immediately remove the plant from the soil and discard the soil. Next, inspect the root system.
Healthy roots will be thick and white in color. If they are thin and grey or dry and black, the roots have died or are straight-up decomposing. Use a thin, clean blade sterilized with rubbing alcohol to cut away dead or dying roots.
Once the dead roots have been removed, proceed with replanting the plant in a clean new pot with new potting mix. Water the plant just enough to help compact the new potting mix, taking care not to overwater the plant.
Continue to monitor the plant. Sometimes, this is enough to save a Cast Iron Plant. Other times, the plant’s root system is too degraded to keep the plant. In either case, learn from your mistake and don’t overwater a houseplant to the point of allowing root rot to set in with future plants.
Dealing With Plants That Received Too Much Light
Addressing yellowing plants due to too much light is an easy fix. Simply move the plant from its current location slightly away from the light source. Take care not to move the plant to a dark corner that receives no light; it’s important to gradually move the plant away from the light source to prevent further stress.
Addressing Plants That Aren’t Getting Enough Light
Dealing with a plant with too little light is simple. Move the plant closer to a light source, not changing the light exposure too dramatically. Remember to keep your Cast Iron Plant out of direct sunlight, even filtered direct sunlight, at all times.
Fixes for Pest Infestations
There are many solutions for pest infestations. Stores sell sticky pads to trap the bugs, but they don’t deal with the underlying issues or any residual larvae in the soil. That said, they can be immediately effective at relieving plant stress, so they can be an excellent solution to be used in conjunction with other treatments.
One of the best natural ways to deal with pest infestations is to use beneficial nematodes. Nematodes are microscopic living beings that transmit via water and eat bug larvae and pupae, addressing the pest species at the source.
Many people use nematodes to eliminate pest species in their yards; I use nematodes to eradicate fleas, ticks, and grubs in my yard. They are easy to apply, safe for pets and humans, and, if applied correctly, keep pest species in check for years on end. They work the same outdoors as they do indoors.
How To Help an Over-Fertilized Plant
If you suspect your plant is over-fertilized, it’s best to repot the plant, removing the potting medium and starting with clean, fresh soil. Always follow the instructions for fertilizing your houseplants; never give them more than is recommended or more frequently than the directions state to use.
I fertilize my Cast Iron Plants less frequently than fertilizers state; I have found that just twice per year is best for my Cast Iron Plant. I fertilize right as they come out of dormancy in early spring and again in the middle of the growing season, typically mid-summer.
Use organic fertilizer to give the plant the best chance at absorbing the nutrients and thriving. Chemicals may briefly boost the plant but are bad for it long-term. Additionally, if you are using nematodes, only an organic fertilizer should be used so as not to kill the nematodes in your plant soil.
With a careful eye and tempered response, you can quickly revive your yellowing Cast Iron Plant and bring it back to its traditional, beautiful deep green hue. Fortunately, if you’re unsure of the cause of plant stress, there are similar treatments for several ailments.
Try a few gradual changes to see if they make a difference in your plant health, and try additional changes if you don’t see improvement after a week.
Remember, Cast Iron Plants need very little sunshine, water, and fertilizer to thrive. Too much of anything can damage the plant, so take appropriate care of it.