Why Are Peace Lily Leaves Turning Black? 7 Causes and Treatments

Most of us grow Peace Lilies to bring a sense of calm and serenity to a space. That’s why it can be incredibly alarming when you see discoloration in the leaves. At that point, you’re left wondering, why are Peace Lily leaves turning black?

There are a few diseases and pests that can cause black spots to grow. However, there are many other factors that can affect the color of the leaves. This includes water quality, lighting, fertilization, and even the size of the pot.

In this article, we’ll walk you through the issues that may cause Peace Lily leaves to turn black. Plus, we’ll cover how to treat the problems.

Peace Lily Leaves Turning Black

Peace Lilies are an incredibly popular species of plant. This is most likely because of how easy they are to grow and maintain.

So, it may be a little surprising when you notice the leaves turn black. Let’s take a look at some of the factors that may have been behind the discoloration.

1.   Watering Schedule

Watering plants

Peace Lilies require a strict watering schedule in order to grow healthy.

As a general rule, the plants need about a cup or two of water every week. Yet, this can change throughout the year.

During the summer, the plant is more likely to lose water quickly. That’s why you need to replace it often.

However, as the seasons change and it gets a little chilly outside, the lilies won’t use as much water. In winter, the plants need watering every two or three weeks.

Under-Watering Your Peace Lily

If your Peace Lilies don’t get enough water, the leaves can turn black.

To help you wrap your head around that, think of the human body. We rely on blood to transport oxygen and other nutrients to our cells.

Plants have a similar transportation system, but they use water as the medium. So, without the liquid, the Peace Lily won’t be able to absorb any minerals from the soil.

In that case, the lily won’t have enough nutrients to support all of its structures. Unfortunately, the leaves are usually the first to go.

The plants will focus their resources on keeping the flower alive and neglect the leaves.

Figuring out if under-watering is the issue is a little tricky. Since most people can’t tell by just looking at the plant, you’ll need to use the finger test.

Poke your index finger about two or three inches into the soil for a few seconds, then pull it out. If it comes out completely dry, all you need to do is add a little water.

Over-Watering Your Peace Lily

Over-watering can also damage your Peace Lilies.

One of the most important structures of any plant is the roots. These are responsible for keeping the lily anchored and absorbing water.

When you add too much water to a pot, the roots can start to soften. That will affect their ability to carry out their functions. Eventually, over-watering may also lead to root rot.

This will have a similar effect as under-watering on the lilies.

To resolve this issue, you’ll need to repot the plant. Take it out of its container and remove any softened roots.

After that, you can replace the soil with a fresh batch and replant your Peace Lily.

2.   Water Quality

Many people don’t consider water quality when taking care of plants. They assume that tap water should be safe enough to keep the Peace Lilies healthy.

While it may be true under specific conditions, this isn’t always the case.

Depending on where you live, your water supply will have a certain hardness level. This measures the concentration of minerals in one liter of the liquid.

When the concentration is under 75 mg/L, then the water is safe to use on the plants. Anything higher than that, and you risk turning the leaves black.

To determine the water hardness, you can buy an at-home test.

You can avoid the hassle of testing if you just switch to using filtered water instead. It’s also possible to use distilled water, but it’s not ideal.

3.   Seasonal Changes

Peace lily flowers in rain

As a Peace Lily owner, you should be familiar with its life cycle. Most plants will bloom in the spring and then shed their leaves and petals during winter.

While this is happening, it’s likely that the leaves will change color. Typically, the structures start out as a bright green and turn into a pale yellow.

As the plant ages, this will be a little different. Instead of the standard color shift, the leaves may turn black.

This is normal for most Peace Lilies and is no cause for concern. Unfortunately, there isn’t much you can do about this discoloration.

However, the problem should resolve itself after a while. The leaves should grow back better than ever come springtime.

4.   Sunlight

To support their growth, Peace Lilies need plenty of sunlight. They rely on it to be able to produce their own energy. However, these plants prefer indirect rays.

Peace Lily leaves don’t have a cuticle, which is a protective layer. Without it, the plants are open to damage from the sun.

As the light shines on the leaves, it’ll start to break down the cells and cause discoloration. Over time, the damage can escalate and the leaves will turn black.

Luckily, there’s an easy solution to this problem. Simply move the plant away from any constant source of light.

Still, you need to keep in mind that plants need some light, so a dark room isn’t an option. Try placing your Peace Lilies on a high shelf or next to other plants for shade.

5.   Fertilization

As we mentioned before, Peace Lilies need a few nutrients to thrive. This includes nitrogen, phosphorus, and potassium.

Without these minerals, the plants won’t be able to grow healthy leaves. Instead, the structures will come out slightly deformed and discolored.

To fix this issue, you’ll need to add nutrients to the soil. For Peace Lilies, you want a 10:10:10 fertilizer, which has all three required minerals in equal amounts.

It’s also important to note that over-fertilization can also damage the plants. The sudden increase in nutrients will cause a pH imbalance that will turn the leaves black.

In general, a few tablespoons of fertilizer every month should do the trick.

6.   Pot Size

When you first purchase Peace Lilies, they usually come in a pot of their own. Over time, the plants will outgrow their vessel.

The roots will spread out until they fill the entire container. Then, as they continue to branch out, they’ll twist and contort over themselves.

Peace Lillies

This will affect the roots’ ability to absorb water and minerals.

To avoid this issue, some people may decide to start off their plants in massive containers. However, this will also have adverse effects.

If you place the Peace Lilies in a large pot, they’ll have a difficult time gathering nutrients. This is because the roots will have to travel further to absorb minerals from the soil.

That’s why it’s best to move your Peace Lilies into slightly larger pots periodically.

7.   Pest Infestations

Peace Lilies are pollinating flowers, which means they rely on insects to reproduce. That’s why the plants produce a sweet sap that’ll attract the critters.

Yet, the lilies can also get attention from unwanted visitors. This includes aphids and mealybugs. These pests will nest on the plants and eat away at the main structures.

Most of the time, the insects will attack the stem. However, it’s also possible that they go for the leaves instead.

When that happens, the Peace Lilies will start to wilt and degrade.

So, you need to make sure that you take care of the issue as soon as possible. To do that, you’ll need a pair of gloves.

Once you have protection on your hands, examine your plants and look for infestations.

Mealybugs look like tiny cottony balls along the plants. This should make them incredibly easy to point out and remove.

On the other hand, aphids tend to be green with white hair-like structures. As you can imagine, finding these critters on green leaves and stems is difficult.

Just be sure to take your time and remove all traces of the infestation.

After that’s done, spray your Peace Lilies with a soapy water solution. The scent of the soap should repel the insects and keep your plants safe.

A few sprinkles of the solution every week should be sufficient.

Wrapping Up

It’s a little disheartening when you notice your Peace Lily leaves turning black. Luckily, if you can isolate the issue, there’s a chance you can treat your plant.

There are a few factors that can lead to this problem. First off, the watering schedule will play a major role in Peace Lily’s health.

Besides that, you also have to check the water quality and sunlight exposure. Still, other factors like seasonal changes and fertilization will come into play.

When you figure out the culprit, resolve the issue as soon as possible. Then, in a couple of weeks, your Peace Lilies should be in tip-top shape.

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