A happy and healthy-looking Calathea is one that stands out as a plant to be admired with luscious, plentiful green leaves. There are occasions, however, when leaves can fade to an unattractive yellow hue desite your best efforts.
This yellowing, also known as chlorosis, occurs when one or more external factors compromise your plant’s ability to produce chlorophyll. Yellow leaves are a warning signal that your Calathea needs some attention. The good news is that, at least in my experienced, the problem can likely be fixed in just a few simple steps.
Why Are My Calathea Leaves Turning Yellow?
In a nutshell, Calathea leaves turn yellow due to stress. Stress can be caused by several external factors including under or overwatering, extreme climate fluctuations, pests, and lack of fertilizing.
To avoid stress and ultimately revive a Calathea with yellow leaves, your plant needs a simple care plan. This includes well-draining soil that is kept moist but not soggy, a bright spot with plenty of indirect sunlight, and high levels of humidity (65% or more). It will also need to be kept away from drafts, checked regularly for pests, and fertilized moderately.
Here’s a closer look at the types of leaf yellowing that can occur if your Calathea has been subjected to stress.
- Over Or Underwatering
- Too Much Direct Sunlight
- Low Humidity
- Do Calathea Like To Be Misted?
- Soil Conditions
- Calathea Yellow Leaves After Re-Potting
- Pests on Calathea
Calathea Leaves Yellow And Curling
If you notice your Calathea leaves curling as well as turning yellow, chances are your plant has been over-fertilized. Whilst regular fertilizing is an important care element for Calathea, too much feeding or a build-up of fertilizer can leave dangerous amounts of salt in the soil.
Ultimately, this salt residue can lead to dehydration. This is where moisture that would otherwise have been absorbed by your Calathea is instead being absorbed by the residual salt.
Yellow Spots On Calathea Leaves
Spots on the top of Calathea leaves that are yellow around the edges are a sign of a spider mite infestation.
These tiny pests are not usually attracted to high levels of humidity, however, this doesn’t stop them with Calathea. The webbing of spider mites can be seen in clusters around node junctions, on stems, and on the underside of leaves when an infestation strikes.
Whilst unsightly, an attack can be treated if caught early on by removing all traces of the pests and pruning back any heavily infested leaves and stems.
Calathea Bottom Leaves Yellow
Too much or too little water is the main cause when it comes to the bottom leaves of your Calathea turning yellow. With underwatering, the bottom leaves will turn yellow because of dehydration. Literally, your plant will be calling out to let you know that there is no water for the roots to absorb.
With overwatering, yellow leaves can occur once root rot has set in. Again, it’s a warning sign from your plant to let you know that something is wrong.
Whilst these plants need to be watered regularly, they can’t tolerate soggy soil that prevents their roots from absorbing oxygen.
Eliminate the stress that overwatering can cause by planting in a well-draining soil mix and allowing the soil to become almost dry between watering.
Causes Of Calathea Yellow Leaves And How To Fix
Now that I’ve explained what your Calathea might look like as a result of being exposed to different stress factors, here’s everything you need to know about how to combat that stress and fix those yellow leaves.
Over Or Underwatering
The watering schedule of a Calathea is akin to the Goldilocks effect: you need to get the amounts just right. Either too much or too little water will cause stress, and your Calathea will make this known to you with a display of yellow leaves showing first at the bottom of the plant.
A Calathea plant needs to be watered regularly to prevent its well-draining soil from drying out completely. Too much water will lead to soggy soil, which Calathea is unable to tolerate and may result in root rot.
Always use a pot or container with plenty of good-sized drainage holes and make sure the soil contains grit, perlite, or bark that will help water to drain more quickly. It’s also a good idea to water over a sink and allow any excess water to finish draining from the bottom of the pot before placing it in either a drip tray decorative pot or planter. Water that pools at the bottom of the pot will not be absorbed by already soggy soil.
How Often Should You Water Calathea?
I’m not a fan of setting a strict regimen for watering any of my tropical houseplants. The amount of water these plants need will vary depending on the temperature, humidity, and time of year.
I find it’s best to check the moisture levels in the soil every few days by inserting a couple of fingers knuckle-deep into the soil. If the soil down there is dry, then it’s time to water. Ideally, the soil will be just damp. If the soil is soggy, check back in on your plant and its soil in a few days.
Bottom Watering Calathea
Bottom watering is a great way of ensuring your plant only absorbs the amount of water it needs. Fill a sink with an inch or so of water. Remove your Calathea from its decorative pot so that drainage holes are exposed and sit it in the inch-deep water.
Remove after an hour or so when the soil is moist.
Alternatively, pour water over the soil of your Calathea and allow excess water to drain free before returning to the decorative pot.
Too Much Direct Sunlight
Calathea grows naturally at ground-level beneath the rainforest canopy. This means they are not exposed to direct sunlight but, rather, are more accustomed to the dappled shade of taller tropical trees and foliage.
When grown at home, Calathea needs a bright spot that is away from direct sunlight. Too much or overexposure to sunlight will cause leaves to become scorched.
It’s a good idea to turn your Calathea periodically to prevent uneven growth.
In terms of tropical plants, Calathea prefers moderate to high levels of humidity. They become stressed by a lack of humidity. Ideally, these plants need between 65 to 80% humidity depending on the Calathea variety.
Check out The Best Plant Humidifiers and How To Use Them.
Kitchens or bathrooms tend to be the places that generate the most amount of humidity in a home but make sure your Calathea is away from the draft of an open window.
If you are unable to maintain this level of humidity for your Calathea, then I recommend investing in a humidifier.
Alternatively, group humidity-loving plants together or place pebbles in the drip tray and add a little water. Both are good ways to increase humidity levels in the vicinity of your plants.
Do Calathea Like To Be Misted?
If you are struggling to maintain moderate to high levels of humidity for your Calathea, I recommend misting with lukewarm water a couple of times per week.
Be sure to mist from the top downwards. This will prevent the bottom leaves from getting over-misted and becoming too wet.
As I mentioned above, an over-fertilized Calathea could result in a dehydrated plant with yellow and curling leaves.
Use a well-balanced, general-purpose houseplant fertilizer. A liquid concentrate with an NPK ratio of 10-10-10 is ideal. I prefer using a liquid fertilizer diluted in water for several reasons.
Firstly, I can fertilize whilst I’m watering. This prevents the risk of soggy soil which would otherwise occur if I used granules that need to be watered in after application. Secondly, liquid fertilizers are fast-acting, meaning they get to work straight away, and results can usually be seen within a week.
In addition, I always allow the excess water (when I’m watering / feeding) to run off down the sink rather than collect it in either the drip tray or decorative container. This means there is less chance of a build-up of fertilizer within the soil.
To further prevent any salt build-up and potential of over-fertilizing, make sure you water in-between feedings. This will help to flush out any build-up of unwanted fertilizer products that could lead to the potential for over-fertilizing.
At the risk of repeating myself here, Calathea needs well-draining soil. This means soil that has the potential to remain moist but not retain too much water, so it becomes soggy.
Coco coir or (not so eco-friendly) peat, combined with orchid bark and perlite or grit is the ideal combination. This will allow excess water to drain through the soil and prevent the soil from retaining too much water.
Bear in mind that the excess water needs an escape route, so make sure your pot has some good-sized drainage holes and always allow this excess water to drain down the sink rather than into the decorative pot or drip tray.
There are plenty of pre-made potting mixes available to buy from your local garden center or online if you’d prefer not to make your own.
I use Espoma’s Organic African Violet Potting Mix. It’s a blend that is marketed for African Violets, however, it is perfectly suited to Calathea and other tropical houseplants too.
What Nutrient Deficiency Causes Yellow Leaves?
Calathea that are deficient in either iron, magnesium, manganese, nitrogen, or potassium may display yellowing of leaves.
Iron deficiency will cause new Calathea leaves to yellow. According to Arizona State University, deficiencies of magnesium, manganese, or nitrogen tend to cause yellowing in mature leaves. When nitrogen deficiency occurs, leaves may droop as well as turn yellow or red. If a lack of potassium is the issue, the edges of Calathea leaves will show yellowing first.
To avoid a nutrient deficiency, plant your Calathea in a potting mix that has been blended with nutrient-rich compost and fertilize regularly.
There are plenty of good-quality fertilizers available that can provide a balance of nitrogen, phosphorus, and potassium macronutrients. You will also find many with micronutrients including iron, magnesium, and manganese.
Calathea Yellow Leaves After Re-Potting
A big stressor for Calathea is repotting. Thankfully, this isn’t required very often.
When you do need to repot your Calathea, you may notice yellow leaves appearing soon after and your plant looking a little droopy and sad.
Give it some time to adjust to its new home before embarking on trying to ‘ix it.
Provided you care for it according to Calathea’s preferences, it is likely to show signs of recovery without too much intervention within a few weeks.
The best way to avoid stress when repotting is to wait until the start of the growing season to repot. Your Calathea will be primed to focus its energy on growing. Although this growth may be inhibited slightly by the repotting process, doing it at this time will help to minimize any stress caused.
I find it’s a good idea to remove tropical plants such as Calathea from pots just after watering. This way, roots are moist and therefore more supple and can be gently eased from the sides of the pot more easily than with dry and brittle roots.
Pests on Calathea
Despite their dislike for humidity, spider mites are highly attracted to Calathea and can cause havoc if untreated or undetected by feeding on plant tissue and extracting sap. This can result in yellowing around the edges of leaves.
Check the underside of leaves and stems, especially at node junctions, for any signs of infestation.
Spider mites themselves are difficult to spot with the naked eye. You may need a magnifying glass to see these tiny moving dots of black, brown, red, or white. Their off-white webbing – that is produced as the infestation progresses — is much easier to see.
To get rid of a spider mite infestation, move your plant away from other plants and then prune the yellow leaves at the base of the stem.
Use Neem oil by spraying it over the remaining affected areas. This will prevent the spider mites from being able to cling to your plant.
Then, using a weak solution of dish soap and water, douse affected areas well and use a cotton swab to gently reach into the nooks and crannies to remove all visible traces of these pests. You will need to repeat this weekly until all signs of the infestation have gone.
Pruning Calathea With Yellow Leaves
Removing yellow leaves includes removing the stem it is attached to. Use a sharp and sterile knife or pruning scissors to cut the stem as near to the base as possible.
Re-sanitize your cutting tools after each cut to minimize any potential spread of disease.
Removing Yellow Leaves from Calathea
Removing yellow leaves from your plant will make it look better. It will also allow it to focus energy on producing new growth rather than exerting effort into healing damaged and unfixable growth.