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Why Does My Indoor Plant Soil Get Hard? (Causes+Risk+Fix)

Despite using suitable potting soil for your houseplants, they get hard after one point in time. Healthy potting soil needs to remain moist and well-aerated. But the plant experiences a lack of water and nutrient absorption when the soil gets hard. This makes the plant weak and tired.

But why does your indoor plant soil get hard? How can we fix the same?

Underwatering, excessive heat, and using old soil often lead to compacted soil. Plants roots also compact the soil around their roots as they repeatedly absorb the water and nutrients. Frequent watering and loosening the soil manually can help prevent the hardening of the soil.

Your duty does not end in just providing the plant with its requirements. You also need to check whether your plant is responding well after receiving the necessities.

If you wish to know the reason behind hard potting soil, keep reading this article. We will also cover information about different ways to aerate and loosen the soil and prevent compaction.



Why does the soil in my house plants get hard?

The potting soil of the houseplant gets hard because it does not get enough moisture for a prolonged period. There are many reasons for the hard soil:

  • Underwatering
  • Excessive heat
  • Clay soil
  • Old soil
  • Build-up of salt
  • The wrong type of soil
  • Aerating materials in the soil died or got flushed off
  • Low humidity
  • Loose soil

Now let us see how they are the causes of hard potting soil.

Underwatering

Underwatering is the most common reason for hard potting soil. Without a good amount of water, your soil will not remain moist and get dry and compact.

Most potting soil contains peat moss which helps absorb moisture and release it slowly to all the roots and the plant.

But if the soil is kept dry for a prolonged period, it will not accept the water anymore. The soil will not absorb any water even if you overwater them.

The best is to correct the watering routine. Water the plant once a week at least. Even if your houseplant is exposed to direct sun, watering once a week will at least keep them from being dry for an extended period.

If you are out of time to perform a regular watering routine, you can use self-watering pots for your houseplants.

Also read: How Often Should You Water Indoor Plants? (Indoor Plants Watering Guide)

Excessive heat

If your houseplants need indirect light, but you have kept them in direct sun for a long time, it will result in hard soil.

It happens mainly during the harsh summers when the intensity of the sunrays is at its apex. The soil tends to get dry very quickly, despite regular watering.

It is more problematic if your soil has clay. This happens when you use garden soil in your potting mix. Clay can make the soil more compact under excess heat.

The first thing to do is, relocate the plant according to its requirements. Some plants do not like heat. But if your plant needs direct sun, water your plant more frequently during the summers.

Add a layer of mulch to the top layer of the potting mix. It will help in retaining moisture for a long time. Mulching also helps in maintaining the proper temperature of the soil.

Too much clay content

It is always recommended that you avoid clay soil. Clay soil is not only responsible for overwatering, but other things too.

Clay can make the potting soil compact. They take too much time to dry. But if you avoid watering for a long time, the clay will become dry and hard, blocking all the air pockets in the soil.

This happens when you use garden soil for your potting soil. Sometimes, garden soil has high clay content. It is better to avoid garden soil for potted plants.

Also read: Can you use garden soil for indoor plants?

Old soil

Over time, the soil starts becoming hard. It is crucial to change the soil once every 1-2 years. If your potting soil does not have any mold or pests, it doesn’t mean that the soil will last forever.

It is better to change the soil of your potted plant in time. In general, you should change the soil once in two-three years. However, it differs depending on the plant type. 

It is okay to change the soil every year for fast-growing plants. Sometimes, fast-growing plants might need repotting every nine months.

But for slow-growing plants, it is not necessary to change the soil every year. You can wait. Some succulents like cacti need repotting every 3 to 4 years.

If you have bought a lot of potting soil for your houseplants and kept aside some for future use, it might harden up the soil. It is better to buy only the required amount of soil.

Build-up of salts

This happens when you over-fertilize your plants or use bad water to water the indoor plants. Fertilizers contain a lot of salts. After the plants absorb the required nutrients, the leftovers remain over the surface.

On the other hand, tap water contains many hard minerals like chlorine, fluorine, and chloramines. These get collected on the soil over time.

These accumulated salts from the fertilizers and water get accumulated on the soil, making the soil hard and blocking all the air pockets of the soil.

As a result, the plant fails to get the water and nutrients from the soil.

The best thing to do is fertilize less. Using less amount of fertilizer will never harm your plants.

Use distilled or filtered water to water your indoor plants. You can use filtered tap water. Or, let the tap water sit overnight for the minerals to evaporate. After that, you can use this water. Rainwater is also a good choice for indoor plants.

Wrong soil type

The soil will get hard when you use the wrong soil type, topsoil, or garden soil. Topsoil is used mainly for outdoor plants.

It has a different texture that will not match the need of the indoor plants. It has a different nutrient mixture unsuitable for houseplants.

Garden soil contains a lot of clay, silt, or sand. Moreover, they lack in nutrients needed by the houseplants. I have already discussed earlier that clay soil plays a significant role in making the soil compact.

Both topsoil and garden soil is heavy weighed soil compared to houseplants. It is better to avoid such type of soil for your indoor plants as they need lightweight soil and different nutrients than outdoor plants.

Aerated materials flushed away

We use peat moss, coco coir, perlite, vermiculite, and many other components while making a potting mix for indoor plants.

These ingredients are responsible for making the soil well-aerated, improving both water drainage and moisture retention.

Peat moss will remain active for 1-2 years. Vermiculite and coconut coir will get washed away and flush out from the drainage holes with each watering.

When these ingredients die and wash away, the aeration decreases. As a result, the soil becomes hard over time. This is the reason it is crucial to replace the old soil with new, fresh soil.



Low humidity

Another cause of hard soil is low humid conditions. Inside the house, the humidity is relatively less than outdoors.

Most houseplants originate from tropical regions and need high humidity. Low humidity will result in the water being sucked out by the surrounding environment.

The more dry the air is, it will suck more moisture out from the plant and the soil. As a result, the soil will turn hard and dry. This mostly happens if your room has air conditioners.

Set humidifiers in your room if there are a lot of plants. It mimics the exact humidity like their native land. Keep them away from ACs and heat generators. You can try regular misting or keeping the potted plants in terrarium jars.

Loose soil

Though loose soil is suitable for flexible root growth, it will result in dry soil. Loose soil helps the roots to grow freely with enough space. But water will not reach the roots of the plants. It will simply come out of the drainage holes. 

The plant will soon start showing signs of under-watering. And then, if you start repeated watering, the soil will clump and become hard in different places.

Risks of compact soil

When the soil of the indoor plants gets hard and compact, it increases a lot of risks for the plants. Some risks will even result in the death of the plant. Let us learn the risks to avoid not making the soil hard.

Lack of water flow

If the soil is too hard, water will not enter the soil and reach the roots. They will just remain still on the surface of the soil. As time goes, the water will just start evaporating into the air.

Overwatering

When your soil becomes stiff, it rejects all the water you provide. The water doesn’t reach the roots.

It remains on the soil and evaporates. In this case, you might think that watering more will solve the problem. But that is not the case.

When you water too much, it will result in soggy soil. The small amounts of air pockets left open will get closed by this excessive watering. They fail to receive oxygen. It seems like the plant is standing in a pool.

If, by any chance, all this excess water reaches the roots, the plant will face another problem named root rot. Due to the compact soil, this water will not go out of the drainage holes and thus remains stuck in the soil, causing root rot.

Decreased aeration

Hard soil does not get enough oxygen for remaining healthy. Compact soil blocks all the air pockets in the soil.

However, the plants photosynthesize to produce oxygen, but that is not all. When houseplants conduct respiration, they take sugar from photosynthesis and join it with oxygen. 

But respiration will not happen with only sugar. The plants need oxygen too. If the air pockets get blocked, there won’t be any oxygen. Ultimately, the plant will not have good growth.

Limited nutrients

The plants not only fail to absorb water in compact soil, but they also fail to get the nutrients. The plant limits nutrient absorption if the soil becomes hard to a great extent. It is essential to understand the condition of the soil before fertilizing.

If you fertilize your plant, but the fertilizer will accumulate due to hard soil, the plant cannot absorb the nutrients. This will further result in over-fertilization.

Plants need a good amount of nutrients to remain healthy. Due to hard soil, limiting nutrient absorption will result in a weak plant with yellow leaves and no blooming.

Reduced root growth

When the soil is well-aerated, the roots get enough space to grow according to their convenience. But if the soil is compact, the roots will not be able to spread and grow flexibly. 

Due to all the blockages of compact soil, the roots may not stop their growth. Eventually, the roots will constantly grow out of the potholes, out of the soil surface, circling until it becomes root-bound.

Some plants will like being root-bound to encourage flowering, but in extreme root-bound conditions, if no action is taken, it can result in the death of the plant too.

What do I do if my plant soil is hard?

Houseplant Care Tip | Aerate your soil!

There are several ways of loosening and improving soil aeration. Different methods depend on whether your soil is stored in a bag for future use or used as the existing potting soil.

For potting soil stored in a bag for future use:

  • Pour some water into the bag and leave it under the sun for a whole day. This can loosen the soil and keep it moist.
  • Another way of loosening the soil is using soap water. Soak a bar soap in a five-gallon bucket of water. When you find the first suds, take out the soap. Add this water to wet the stored soil and leave it for a day. This will loosen the soil.

For potting soil already in use:

  • Loosen the soil by poking a fork, stick, or chopstick into the soil. Be gentle and careful while doing it. Try avoiding harming the roots.
  • Now water your plant well, especially on the poked areas, so that the water can moisten the soil and then flow out of the drainage holes. If water doesn’t flow out of the holes, poke the soil again. It will help to aerate the soil and allow enough oxygen flow.
  • If the pot is small, lift it and keep it in a tub filled with water. Keep it like that for not more than an hour. After that, take it out and keep it in a container filled with water for another hour. This method will help loosen the soil, and the soil will also absorb moisture in the second hour.
  • If your pot is big enough, leave a garden hose with dripping water over the surface of the soil. The dripping water will get absorbed by the soil as time goes and the soil will again get back its moisture.
  • If you have not repotted your plant for quite a long time, it is time to replace the old soil. For making a new soil mix, mix 1 part of potting soil with 1 part of vermiculite or perlite and 1 part of sphagnum moss. Water the soil just to make it moist, not soggy. This will help in good aeration, good drainage, and good moisture retention.

Using vermicompost to aerate the soil

Vermicompost is an excellent ingredient for keeping the potting soil loose and aerated. It consists of earthworms that constantly crawl in the soil and keep the soil light, loose, and well-aerated.

For making vermicompost:

  • Collect vegetable and fruit scraps and peels. This will help the worms to digest quickly. Avoid using dairies, oils, meats, and citrus fruits. 
  • Put them in a container measuring 24” by 18” by 8” and between 5-10 gallons. A shallow container is better than the deep one.
  • Get live worms. You do not have to collect them. They can be bought from the market. Buy them and add them to the compost container. Now close the container. It will take 3-5 months for the compost to become ready for use.

How do you keep potted soil from getting hard?

Here are some basic ways to keep the soil healthy.

Relocate the plant

If excessive heat is the reason behind compact soil, try relocating the plant. Most houseplants tolerate low to medium indirect light. Keep your plant near the north or east-facing window. 

If your plant is sitting near a south or west-facing window, keep it a few feet away from the window. Pull down curtains or use Venetian blinds to create a filter for direct sun.

Mist regularly

Misting can help in keeping the soil from getting stiff and dry. Misting will help conduct good humidity; along with that, misting the soil will help maintain soil moisture.

Follow a good watering routine

Water your plant 1-2 times a week, depending on the soil moisture and the plant’s requirements. Try to keep the soil moist instead of making it wet.

Repot the plant

Repotting will help improve the plant’s condition. With fresh soil, the plant will not face any risk of compact soil anymore. Only keep these in mind:

  • Spring is the right time to repot as it is the growing season; transplant shock can be handled and recovered easily.
  • Fast growers need to be repotted once a year or sometimes every 9-10 months, whereas slow growers can wait for 3-4 years.

Final words

A good, well-aerated, lightweight soil is the key to the remarkable growth of indoor plants. A compact soil will affect the growth of the plants as it prevents the absorption of nutrients and water.

It is essential to use suitable potting soil, sometimes loosening and changing the soil whenever necessary. This will help in good air circulation, easy absorption of water and nutrients, and receiving fresh nutrients along with fresh soil. Altogether, it will keep the plant healthy and thriving.

FAQ

Will aerating damage the roots?

If aerated with a fork or stick, there are risks of root damage, as you are unaware of the exact location of the roots in the soil. While using forks or sticks, be very careful. Try sifting the soil slowly.



How often to loosen the soil?

There is no specific time to aerate. You can loosen the soil anytime. You just need to keep the soil in check by poking your finger into it. If it feels hard, it has started compacting.

Your focus should be to prevent compaction instead of treating it. It will help you keep away from the risks of compaction.


Ref: Soil compaction studies, Effect of Soil Compaction, Impact of Soil Compaction on Root System, Responses of a root system structure to soil compaction, Soil and Plant Nutrition, Soil and plant growth.