A potting mix is not just dirt in a bag. Each type in the garden or hardware shop has its own distinct characteristics. To complicate things, potting mix packages include a plethora of misleading marketing terminology and labelling. If you don't have hours to spend reading the components of each option (I certainly do not!), this article provides real world insights into the best choices.

Potting soil may not seem to be a very thrilling subject, but it is really important for the health of your plants. Potting soils were created for plants that grow in pots and have different requirements than those planted in the ground.

All potting mixes are not equal. Succulents, for example, need different soil than ferns. Different potting mixes were developed to meet those requirements. Knowing what's in your potting soil can help you provide your plants with the nutrients they require to prosper and perform their very best.

Ingredients of potting soil mix and their functions

Most traditional potting soils contain sphagnum moss (peat moss), perlite, vermiculite, and coco coir, which aren’t always good for the environment. Fortunately, there are eco-friendly and peat-free blends you can use instead. 

• Perlite

Perlite is typically used to aerate compost, but it can also help in retaining some water. It is perfect for making draining potting mixture for plants that need good drainage, such as cactus and succulents. It is also very helpful in making an aired-out compost for seedlings.

• Sand

Sand is, of course, a big part of any potting soil mix. Coarse sand is a common option for potting mixtures because it offers good drainage and aeration. This kind of sand usually has big, kind of angular particles that make the soil porous and airy, allowing water to pass through easily. Coarse sand is good for plants that need good drainage, such as succulents, cactus, and Mediterranean herbs.

On the other hand, fine sand has smaller particles, which gives the soil a more dense character, allowing it to hold more water. It is great for plants that prefer a moisture rich environment, such as ferns and certain houseplants.

• Peat Moss

Practically every potted plant you buy, as well as the bagged potting mixes, contains peat moss. This is because peat moss makes the soil hold moisture and provides your plants with that extra support they need to grow. It is particularly good for growing flowers, fruits, and vegetables because of its moisture-retaining qualities. It is not, however, good for the environment.

So what can you do instead? There are packaged potting mixes that do not include peat moss, so check the label before purchasing. They may alternatively include other plant based elements like coconut coir (a fibre derived from discarded coconut husks), recycled paper fibres, and compost. You may also try making your own mix using these options.

• Vermiculite

Anyone who has dealt with potting soil mix has likely seen the small "blocks" or bits of gold it contains. These light and airy particles are known as vermiculite, which is an essential commodity in gardening. While they may not be worth their weight in gold they are highly revered for their numerous benefits including aeration, water and moisture retention and being rich in nutrients.

• Coir

Sometimes also known as coco coir or coconut coir, it’s a wonderful replacement for peat moss. It has a hoard of benefits, proper aeration and moisture retention are a few that can be named. 

Choosing the best mix for indoor plants

There are four key elements that are vital to your plant's health.

Good drainage and the right levels of moisture: Moisture retention is as vital as aeration. It is important to realise that soil should not become soggy, but should be able to retain moisture in order to encourage plant growth and health. Look for mixtures that have ingredients like peat moss, coconut coir, or composted bark that can retain moisture without getting soggy. This helps in maintaining the plants' hydration levels.

Good structure so the roots can breathe: Your indoor plants need loose, airy soil in order to grow new roots. A  soil that is too dense can hamper the development of the plant. Good potting mixes should include aeration promoting ingredients such as perlite, vermiculite, or river sand. Adequate ventilation allows oxygen to reach the roots, which promotes proper growth.

Good support so the roots can spread out: The texture of the potting mixture influences the growth of roots. It should be movable enough to enable roots to pass through yet solid enough to offer support. Avoid combinations that are very thick or compressed. When purchasing, touch the mixture with your hands. You should be able to easily insert your fingers into the mixture. It should also be somewhat wet and warm.

The right balance of nutrients: Your potting mix should have nutrients for the plants to grow. Choose a potting mix with added organic fertilisers like manure, compost, or vermicompost.

Benefits of the right potting soil mix

• Better plant health

If your plant is getting the right potting soil, it is able to focus all its energy on growing instead of fighting to survive in unfavourable conditions. This is especially important when trying to revive struggling or unhealthy plants. You will see greener leaves, stronger stems and healthier roots as soon as you pick the right soil. 

• Lesser chances of pests and diseases

Potting soil is sterilised at the time of production, which significantly reduces the chances of your plants contracting soil borne pests, especially when compared to normal garden. With a sterelised potting soil, you can sit back and relax. Instead of worrying about the pests, you can devote that time to ensuring your plant grows healthy. 

• Nutrient rich soil

The whole purpose of potting mixes is to provide a properly balanced supply of all the nutrients that your plants need to grow. Garden soil can lack all of these nutrients and also doesn’t contain the appropriate nutrients for disease prevention. A sterelised potting mix that contains perlite, vermiculite, and all other ingredients will keep your plant healthy and happy. 

• Less risk of waterlogging

When the soil is more aerated, it does not retain water. A well drained soil is particularly beneficial to plants. It lowers the probability of root rot and other root diseases. This is why you should choose the finest potting mix for plants that contain sand, perlite, and other coarse materials.

• Faster Growth

The finest soil for potted plants has organic matter such as cocopeat, coir, and vermicompost, which slowly releases nutrients into the soil for the plant to absorb. This is why potting mixtures allow plants to grow much faster.

Frequently Asked Questions

1. How to store potting soil?

Opened bags should ideally be stored in sealed containers that are shut with tape. On the other hand, if your bag hasn’t been opened yet then you can just store it in any area that is cold and dry.

2. Can potting soil be reused?

You may reuse potting soil if you take proper care of it initially. Before planting, make sure there are no pests and that the pH level is appropriate. If there are difficulties with the soil, just treat it for pests and mix it with new soil to reuse.

3. What is the difference between planting soil and potting mix?

The potting mix is designed to stand alone rather than mixed with existing soils. It is a self contained solution that provides potted plants with everything they need to develop and flourish. Garden soil is intended to be spread around.

4. Is potting soil better than compost?

Because of its composition and choice of nutrients, potting soil is often used by gardeners to maintain plants grown in pots. Compost, on the other hand, is high in nutrients that may enrich the soil and promote the growth of plants, especially those that are planted outdoors or in big pots.

5. How to tell if potting soil is going bad?

Look for indicators such as a bad odour, visible mould, or the development of fungus. These symptoms may indicate that your used potting soil needs revitalisation. If your potting soil remains damp in the bag, it may grow mould or other unpleasant contaminants.

6. What is the main ingredient in potting soil mix?

Most high quality potting mixes consist of mostly composted pine bark. The bark is a byproduct of the plantation wood business; thus, it's local (not imported), renewable, and sustainable.

7. Can I use a potting mix without soil?

Potting mixes do not contain any soil. Potting mixes are used for container planting, especially for orchids, succulents, and cacti that need good drainage.

8. How many years is potting soil good for?

It's best to use opened potting soil within a year or two for optimal plant health.

Final thoughts

Plants need nutrients just as they need light and water. The soil you pick gives your plants the structure that allows their roots to expand and access air and water.  Soil is not just dirt and differs from the natural soil in your garden. Despite being widely referred to as "potting soil," most commercial potting soils contain no soil. They're frequently made of wood and strengthened with chemicals that help aerate the soil and supply fertiliser to the roots. These soils are lighter than garden soil and are called "potting mix." I hope this guide helps and you can pick the perfect soil for your plants.