If you have plants, you likely have either a love, love-hate, or a hate relationship with terra cotta pots. Personally, I love terra cotta pots. I think they add a beautiful rustic boho vibe to my plants while also being functional and relatively inexpensive.
However, I also know many gardeners that absolutely hate the look of these pots. I will say one of the worst parts of terra cotta is keeping it clean.
Since terra cotta is porous, it is prone to developing white residue on the inside and the outside of the pot. It can also grow green algae and blackish mold. In this article, we will discuss what causes these issues and the best ways to tackle them. Let’s dive in!
- What Is The Residue On My Terra Cotta Pot?
- How to prevent residue from forming on my terra cotta pot?
- Does Residue Harm The Plant?
- How to get rid of residue on your terra cotta pot?
- When You Shouldn’t Use Terra Cotta For Your Plants
- What Plants Love Terra Cotta?
What Is The Residue On My Terra Cotta Pot?
If your terra cotta pot is coated in a white residue, don’t panic. It’s nothing more than salt deposits, and won’t hurt you or your plant. When you water your plant with hard water, which is what most tap water is, dissolved salts end up in your soil.
Since terra cotta is porous, some of the water will evaporate through the sides of the pot. When this happens, the water goes into the air and the salt is left behind. This process can happen with any porous material and is called efflorescence.
While some people hate this look, others actually pay more for it. You may see it marketed in hobby stores as a patina finish or a white terra cotta pot. Personally, I’m not a fan of this look, but if you are, terra cotta pots will be perfect for you!
If there is a green film on your terra pot this is due to algae. While it’s less likely you will encounter algae indoors, it can definitely be an issue outdoors or in an area near a humidifier. Algae won’t hurt your pot or your plant and I personally think it adds a little something extra to your pot. Kind of like 2 plants for one.
Occasionally, with terra cotta, you will also see a black film or a white fluffy substance on the outside of your pot. This is mold. Since terra cotta is porous and the material is often damp, it is an ideal place for mold to grow.
Mold on the outside of your pot shouldn’t hurt your plant, but you don’t want it spreading through your house. No one likes the look of mold, so this is one you definitely want to get rid of.
How to prevent residue from forming on my terra cotta pot?
To prevent salt from building up on the outside of your pot there are a few methods you can try. The first is to use filtered water or rainwater when you water your plants. Since the main cause of white residue is salt and most of that salt is coming from your tap water, eliminating tap water from your plant care routine can majorly cut down on the amount of salt that is left behind on your pot.
The second way you can prevent salt buildup is by using a diluted fertilizer. There are lots of minerals in fertilizers and many of them are not absorbed quickly enough by the roots of your plant before the water is evaporated from the pot.
Reducing the amount of fertilizer you use in half but applying it twice as often will get your plant the nutrients it needs, but in smaller doses, so the plant is able to absorb more before water evaporates.
Another option is to simply seal your terra pots with either Rustoleum or flex seal. While this will defeat the purpose of using terra cotta for root rot prone plants, it will allow you to use them with plants that normally don’t do well in porous containers.
Since the porousness of terra cotta is what allows the salt to form on the outside of the pot, sealant will easily solve the issue.
Algae and Mold
To prevent algae and mold on your pot, you can seal it with rustoleum or flex seal. This will prevent water from evaporating through the surface of the pot and providing the algae and mold with water. Without water, the mold and algae won’t be able to survive and won’t grow.
You can also prevent algae by regularly spraying the outside of the pot with diluted bleach. This will prevent algae and fungus from growing.
If your plant is tolerant of sunlight, you can also place the pot into direct sunlight. Since algae needs indirect light to thrive, direct sun will kill it and prevent more from growing.
Does Residue Harm The Plant?
Having salt buildup on the outside of your terra cotta pot won’t hurt most plants. The exception to this is trailing plants whose stems may come in contact with the salt. Salt is not good to have directly on stems, leaves, or roots of plants.
Salt buildup on the inside of your pot shouldn’t hurt your plant either, but it could be a sign you have too much salt in your soil. Try to flush your soil once a month to cut down on the amount of salt.
To flush your soil, use 4x the amount of filtered or rainwater your pot can hold. Slowly pour the water into the pot, allowing it to drain out of the drainage hole. This should flush any salts or other unwanted minerals from your soil.
Having algae on your terra cotta pot will not hurt your plant in any way. Even if trailing plants touch the algae, they will be fine. It’s basically just another plant hanging out nearby.
Mold and fungus
Having mold and fungus on your pot is not ideal. It can harm your plant if it reaches the roots and breathing it in can be bad for you. You will want to get rid of any mold or fungus on your pot as soon as you spot it.
How to get rid of residue on your terra cotta pot?
White residue/salt buildup
The best time to rid your pots of salt buildup is in the spring when you are repotting your plants. Be sure the pot is empty when trying to remove salt buildup as this method could hurt your plant.
To start, you will want to create a mixture of 1 part vinegar to 4 parts water. Place your empty pot in the solution and allow it to soak for about an hour. This will loosen the top layer of residue and allow it to come off when you get to the next step.
For step 2, you will want to scrub the pot with a bristle brush. It may take a lot of scrubbing to get all the salt off, so just do what you can and then place the pot back in the water to soak again. Depending on the size of your pot and the amount of residue that has built up, this process could be a long one.
If your pot is relatively small and you got it at a place like Lowes or Home Depot it may actually make more sense to simply replace the pots every year and donate the white ones to a charity or post them for free in a local community group.
Removing algae is a relatively easy process, especially compared to the salt. Simply wash the pot in hot soapy water the same as you would your dishes. The algae should come off pretty easily with a little scrubbing.
To remove mildew from terra cotta, you will want to either soak the pot in diluted bleach for 10 minutes, then take it out and wash it with soap and water. Or, you can spray hydrogen peroxide onto the mold. Let it sit for approximately 5 minutes, and then wash it in hot soapy water. Both methods should work well at removing mold and fungus.
When You Shouldn’t Use Terra Cotta For Your Plants
If you love terra cotta pots, you may be tempted to use them for all your plants, but there are times that terra cotta isn’t an ideal material for plants to grow in. If you have a plant that prefers being kept moist, like peace lilies or plants from the elephant ear family. Terra cotta pots can actually cause these plants to dry out too quickly.
If you really want to use terra cotta on all your plants, there is a compromise. Sealing them with rustoleum makes them nonporous and allows them to be used with moisture-loving plants.
What Plants Love Terra Cotta?
There are some plants that really thrive in terra cotta plants. Most succulents, cacti, philodendrons, and snake plants do really well in terra cotta. Since they do well in fast-draining soil, it makes sense that added drainage would help them do even better.
A good rule of thumb when deciding if terra cotta is right for your plant is to check whether your plant prefers dry or fast-draining soil. If the answer is yes, your plant will likely thrive in a porous terra cotta plant.