Why are My Terra Cotta Pots Turning White?

Terracotta pots are beautiful for plants because of how they look. Many growers also like them because they help reduce the risk of overwatering.

However, if you’ve been growing plants in terracotta pots for a while, you’ll probably notice that they turn white after some time.

Why are your terracotta pots turning white? The white residue on terracotta pots is called efflorescence.

It forms when dried minerals, salts and calcium build up due to hard water and fertilizer.

Fortunately, the white residue is not harmful to plants. And you can easily remove it by using a vinegar or bleach solution.

What is the White Residue Build Up on Terracotta Pots?

The white residue that builds up on terracotta pots are mineral salt deposits left from hard water or fertilizers. Technically, this white crust is called efflorescence, although some people refer to it as patina.

This happens because terracotta pots are porous. And although they may look like they’re completely solid to the human eye, there are very tiny holes in terracotta that allow water and minerals to seep though.

This is what makes the pots appealing to many gardeners since it helps prevent overwater.

Once the water dries up or evaporates, what you’re left with are the dried up mineral salt deposits. This is what forms the white crust or residue on terracotta pots.

Some people like the look the white residue leaves because it gives their pots age and character. Other people don’t like it and prefer a cleaner look.

CHART - Why is My Terracotta Pot Turning White
Chart of Why is My Terracotta Pot Turning White

 

Is the White Residue on Terra Cotta Pots Harmful to Plants?

Of course, beyond the way it looks, the big question is whether the white crust that develops on terracotta pots is harmful to plants?

The answer is no. The white residue that forms is not harmful. Therefore, you can leave it there if you like the way it looks.

That said, it tells you that there’s a lot of excess minerals that are building up in your soil.

This is important because too much salt accumulation in the soil will ultimately damage your plant’s roots.

In general, plants don’t like salts. And these salts can eventually burn your plant.

Therefore, when you see white crust or residue forming on the sides of your terracotta plant, it is a good idea to investigate what the cause is.

In most cases it is one of two things:

  • Your tap water has too many minerals (hard water)
  • You’re using a lot of fertilizer

The first reason is isn’t always true. That’s because the amount of chemicals in tap water varies per municipality. So, it may be specific to yours.

If this is the case, you have a few options:

  • Use rainwater. You can use a rain barrel or something similar to collect rainfall and use it to water your plants.
  • Filter or purify your tap. You can install a water filter on your faucet to remove the minerals.
  • Use distilled water. While this solution works, I don’t recommend it as it can get expensive especially if you have big plants.
  • Let the chemicals in tap water evaporate first. To do so, let tap water sit at room temperature for at least overnight to 24 hours. This will allow the chemicals to evaporate before you water your plants.

The second reason that can cause the white residue on terracotta pots is fertilizer.

Fertilizers contain salts. Manufacturers use these salts because they’re the most efficient way to transport nutrients so the plant can absorb them.

However, after the nutrients are taken by the roots, the salts are left in the soil.

So, the more you feed your plants, the more salts you’re adding to the soil (in addition to giving your plant’s nutrients). And too much salts can cause fertilizer burn which will eventually damage the roots.

This can make it dangerous (and why I always warn against over fertilizing plants).

Thus, if you notice white residue in your terracotta pots due to fertilizer, you have a few options.

  • Use an organic fertilizer
  • Try using compost and worm castings instead of fertilizer
  • Flush your soil regularly

 

Do All Terracotta Pots Turn White?

Efflorescence will eventually develop if you use hard water or fertilizer with your terracotta pots.

Because not all homes have hard water in their tap, this may or may not happen. Similarly, if you don’t use fertilizer or use one that does not leave a lot of salt reside, the pot may not develop a white crust. Or if it does, it will be minimal.

That said, the amount of white crusting on terracotta pots will also vary depending on how the pot was made.

If it was manufactured by machines, it is less likely to develop lots of white residue because the clay is packed in tighter. The compact nature means fewer and smaller holes for the water and mineral salts to get through.

However, this also means the pot is less porous. Therefore, it won’t let as much water seep out.

As such, its effects on preventing overwatering is less than traditionally baked terracotta pots.

On the other hand, terracotta pots baked at lower temperatures tend to develop more efflorescence. Therefore, handcrafted pots will usually have more crusting compared to those mass made by machines.

 

How to Clean and Get Rid of the White Residue Buildup on Terracotta Pots

Fortunately, it is not difficult to clean or get rid of the white residue that builds up in terracotta pots. You also don’t need many tools.

However, it does take a little work and time.

Here are the supplies you’ll need:

  • White vinegar
  • A sink, tub or bucket that’s big enough to fit your pot
  • Pot brush
  • Dishwasher (although you may or may not use this)

 

Related

 

Remove Any Dirt from the Pot

The first step is to remove any dirt from your pot.

If you’ve been using your pot for plants for a while, there’s bound to be soil, dirt, dust and debris inside and outside the pot. Therefore, use the pot brush to clean as much of the dirt as you can.

You don’t need to spend a ton of time here or get it perfect here.

The goal is to get rid of the bigger chunks, debris, and other particles.

 

Soak Terracotta Pots in a Vinegar-Water Solution

Once you’re done brushing off the dirt from the pot, mix:

  • 1 part of 5% vinegar
  • 4 parts of water.

You can scale this up or down depending on how many pots you wish to clean and how big the pots are.

The more concentrated the vinegar, the faster it will clean the pot. The more diluted it is, the longer you’ll need to soak the pot.

Submerge the pot into the solution.

You’ll hear some fizzing sounds or bubbles which is the chemical reaction at work. Basically, this just tells you the vinegar is working.

Check the pots every 20 minutes or so.

The vinegar will loosen the white crust from the surfaces of the pots. However, you’ll still need to scrub the residue off with your pot brush.

Therefore, check the pot and try scrubbing. Once the white residue easily scrubs off the vinegar is done doing its job and you can easily remove the remaining crusting with the brush.

If the white residue is still stuck, leave the pots in the soak another 20 minutes.

Keep doing this until it is easy to scrub off the white crust using the brush.

 

Put the Pots in the Dishwasher

This is a final step.

Running your terracotta pots in the dishwasher using a wash cycle will clean and disinfect them. It will also remove any remaining smell of vinegar (if there is any).

 

If You Don’t Want to Use a Dishwasher, Scrub the White Residue Off

An alternative to using the dishwasher is to clean them with soap and water the old fashioned way. Basically, treat the pots like your kitchen pots and pans and clean them like you would your dishes.

This will get rid of any pathogens and disinfect your pots so they’re clean and ready to use again.

CHECKLIST - How to Get Rid of White Residue on Terracotta Pots
CHECKLIST – How to Get Rid of White Residue on Terracotta Pots

 

Why Should You Clean Terracotta Pots?

Cleaning your terracotta pots means the white residue will disappear.

Thus, some people hold off or don’t want to clean their pots because they like the look produced by the white crusting.

While this works for a time being, you’ll eventually want to clean your terracotta pots. That’s because like all things they get dirty.

While dirt from soil is usually not a problem especially for plants, it does increase the risk of harboring pests and diseases.

And if one of your plants happens to get fungal root rot, the next plant that ends up in that pot will suffer the same fate.

Therefore, reusing pots over and over for your plants is not a good idea.

As such, it is often good practice to clean and disinfect your pot after moving or repotting a plant. This ensures that the next plant that goes in there has a clean living environment.

 

How to Prevent Terracotta from Turning White

Efflorescence occurs in terracotta pots for a few reasons. For this most part, it is the porous nature of the clay allows water and tiny particles to get through the pot.

This is why the white crust does not develop with plastic or metal containers.

But in addition to the clay material and the tiny holes in its structure, there needs to be a few things to happen for the white residue to develop.

  • There has to be water (or some kind of liquid)
  • Presence of mineral salts that dissolve in water
  • Water evaporating leaving the mineral depots (which forms the white crust)

So, the best way to prevent your terracotta pots from turning white is to limit, reduce or eliminate one or more of these factors.

Here are some ways to do it.

CHECKLIST - How to Prevent Terracotta Pots from Turning White

 

Use Rainwater or Distilled Water to Water Your Potted Plants

If the cause of the efflorescence is hard water or excess minerals in the water you use for your plants, change it.

Instead of using tap water you can use rainwater. If you don’t get regular rain where you live, you can filter or purify your tap water to get rid of the minerals.

Another option is to let the tap water sit at room temperature overnight or longer. This way, the minerals will have evaporated by the time you water your plants.

 

Go with Weaker or Gentler Fertilizers

If hard water is not the issue, then check your fertilizer.

Fertilizers leave salts in the soil. This is especially true for synthetic fertilizers.

Just as importantly, the amount of fertilizer you use, how much you dilute each dose and how often you feed your plant all factor into how much white crusting develops (and how quickly it develops).

Therefore, you can reduce the white crusting by:

  • Using less fertilizer
  • Apply less when you do or diluting it
  • Not feeding your plant as often

Another option is to use weaker fertilizers. These tend to contain less salts, so the white residue does not accumulate as much.

Alternatively, you can switch from synthetics to organic fertilizers which contain much less salt. Note that organic fertilizers are more costly and don’t contain as much for the same amount of product.

You can likewise fertilize via the soil instead. You can use compost or worm castings so you don’t need to use as much fertilizer (or skip it altogether).

Finally, instead of adjusting your fertilizer and feeding schedule, you can flush the soil regularly, This will get rid of the mineral salts in the soil.

 

Regulate Humidity

Humidity can also help reduce the amount of white crust that builds up on your terracotta pots. However, it does not play a significant role.

Low humidity causes more evaporation. Therefore, this increases the rate at which the water dries up, leaving more salt residue in the surfaces of the pot.

On the other hand, when there is more moisture in the air, water will take longer to evaporate. This will allow some of the water to seep out of the pot (with the dissolved minerals) before it evaporates.

Therefore, the mineral salts are not left in the pot and you don’t get as much white residue.

 

Apply Surface Sealers to Terra Cotta Pots

Surface sealers work by sealing water out of the surface you applied it on. Therefore, this prevents water from getting to the pot and the tiny holes in its structure.

However, it is also worth noting that using a surface sealer will effectively negate the porous nature of terracotta pots. This means they won’t help in letting moisture escape to prevent overwatering.

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