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Potting Mix Guide: How to Customize and Choose Potting Soil

Gardening soil can make or break a houseplant, which is why gardening experts know their potting soil like the back of their hands. Thanks to years of experience, they can look at the ingredients listed on a bag of potting soil and know which plants will thrive in it. Many even customize their potting mix to match the needs of each type of plant.

The rest of us reluctantly pick up a bag of “all-purpose soil mix” at the garden center and call it a day. But there is a middle ground. Let this guide be an informative shortcut that will let you tap into all that gardening knowledge and understand your plants’ needs better.

In this article, we’ll explain what makes a good potting mix, break down all the different types of soil ingredients, and even give you a few custom soil mix recipes you can craft at home. So, from now on, you too will walk into your gardening center with confidence.

Garden soil and houseplant soil - is there a difference?

Potting Soil 101 repotting a plant

The question in every beginner gardener’s mind is, “Can’t I just use the soil from my own garden?” The short answer is no, as the plants we grow indoors live in very different conditions and belong to different species from our outdoor plants. Here are the general differences:

  • Garden soil is dense and heavy. Indoors, plants dry out much slower, and as a result, a houseplant planted in garden soil is more likely to be overwatered and waterlogged, which leads to root rot, brown leaf tips, and other issues. In addition, without natural aeration provided by earthworms, garden soil will become compacted, stifling the development of the plant’s root system. Last but not least, garden soil may contain fungi spores, pests, and other pathogens that can kill your indoor plants.
  • Houseplant soil is light and airy. It contains ingredients that support the root system by providing your plants with space for developing roots and breathing. Indoor potting soil is formulated to facilitate water drainage and prevent root rot. Potting soil is also sterile and may even contain materials that prevent fungal infections and other diseases.

That’s why it’s generally better to buy a bag of potting soil, ideally something labeled, “houseplant mix,” “indoor potting soil,” or “well-draining soil.” 

Potting Soil 101 potting soil on table

If you’re looking for a more budget-friendly option, you can opt for generally-lighter container gardening soil and then augment it with ingredients like perlite, peat moss, or orchid bark that promote better drainage and aeration. If all this sounds overwhelming, worry not. We’ll explain what these ingredients do and how to use them further on.

What makes a good potting mix?

For your houseplants, look for a potting mix that’s light, well-draining, and full of nutrients. This means that the potting mix may contain no actual soil at all; instead, look for a mix of soil-less components like coconut fiber, peat moss, vermiculite, perlite, sand, etc. Some brands also contain fertilizer, so you won’t need to add your own. If the bag doesn’t list the components, it’s best to steer clear of that brand and choose something else.

Most houseplant mixes are already pH balanced, so you don’t need to worry about altering that. Just know that most houseplants thrive in the neutral to slightly acidic pH range - from 6.0 to 7.0. The pH of the soil can be checked using a soil test kit that can be purchased online or at gardening centers.

Potting Soil 101 sacks of potting soil and plants

Wondering if you should buy organic soil for your houseplants? Since you’re not going to eat your indoor plants, we don’t see a point in abstaining from synthetic ingredients and fertilizers. But the ultimate choice is up to you, just keep in mind that organic soil mixes and fertilizers tend to be a bit more expensive.

What type of potting mix is right for my plants?

So, you arrive at the gardening center, and you see houseplant soil mixes for different plant families: one for cacti, orchids, and aroids. All of these potting mixes have different proportions of materials and varying ingredients, and they can be handy for consumers, as you simply pick up a bag of cactus soil for your cacti and succulents and call it a day.

Generally speaking, these are the differences you can expect to find in terms of ingredients and properties:

All-purpose potting soil

Potting Soil 101 All-purpose potting soil
All-purpose potting soil works well for most common houseplants. These are not particularly useful if you’re looking to cater to specific plant families, but you can always use them as a base for your custom-made potting mix.

​Seed-starting soil

Seed-starting soil is exactly what it sounds like - a potting mix that creates the perfect environment for seed germination. This type of soil doesn’t contain many nutrients, urging the roots to expand quickly.

Cactus and succulent mix

Potting Soil 101 Cactus and succulent mix
Cactus and succulent mixes imitate the kind of soil that cacti naturally grow in. They often have a base of peat moss or coco coir that provides moisture but dries out quickly to prevent overwatering. Cactus mixes also contain inorganic materials like pumice, sand, and perlite to aerate the soil. These types of mixes sometimes also work for citrus plants that also need good drainage.

Orchid mix

Orchid mixes may seem niche, but they are great for most epiphytic plants (plants that naturally grow on tree trunks). Many universally loved houseplants, such as monstera, pothos, Scindapsus, and philodendron are also epiphytic. Orchid mixes are heavier on rocks, bark, and clay to provide the roots with plenty of air circulation.

Related Article: Spend Less Time on Lawn Care and Maintenance - 7 Best Tips

Ingredients for customizing and improving potting soil

Now you’re ready to purchase the type of soil you need for your houseplants. But there’s an even better way to cater to the needs of specific plants - soil additives. This step does involve some mixing and experimentation, so we understand that it’s not for everyone. However, knowing which specific ingredient to add can help you tackle many houseplant foes, such as over- or underwatering, root rot, quickly wilting leaves, and the list can go on and on.
Potting Soil 101 soil ingredients

We describe what each soil additive does for your houseplants below:

1. Peat moss

Harvested from peatlands, peat consists of sphagnum that has died and broken-down thousands of years ago. Peat moss is relatively lightweight while also being capable of retaining moisture and providing some nutrients. This makes it a great mix in most potting soils.

Although peat moss has been abundantly used in the past, gardeners are now stepping away from it due to its unsustainability. It takes ages for peat bogs to recover, which is why some countries, such as the United Kingdom, are going to ban selling peat moss.  Luckily, the next two ingredients listed can fully replace it.

2. Sphagnum moss

Potting Soil 101 plant in Sphagnum moss

Sphagnum moss is a group of mosses that live in swamps or bogs. The live moss is harvested and sold dried and packed into bricks or still living. The advantage of sphagnum is that it’s like a living sponge, so you can rehydrate it in water and add it to your potting soil in place of peat moss or coco coir, or use it as is for houseplant propagation.

Unlike peat moss, sphagnum can be sustainably harvested because it can regrow fast.

3. Coconut coir

Let’s wrap up with peat moss alternatives. Coco coir is a light and fibrous medium taken from the outer husks of coconut shells. Like peat moss, it has the very useful property of retaining water without it becoming compacted or heavy. Coco coir is packed into bricks; you can crumble the bricks into smaller pieces and mix the fibers in the soil.

Potting Soil 101 coco coir, orchid bark
Best of all, coco coir is both organic and sustainable. Coconut fibers are usually considered a waste material and discarded, so using them is actually beneficial for the environment.

4. Activated charcoal

If your plants tend to suffer from fungal infections, bacterial infections, or root rot, mixing in some of this magic heat-treated charcoal will protect them. Activated charcoal works by absorbing excess moisture from the soil, and adding only a little bit will do the job.

5. Volcanic rock - pumice and perlite

Pumice is a lightweight, naturally occurring volcanic rock added to the soil for aeration. It leaves tiny pockets of air in the soil which will let the roots breathe and grow freely. Perlite, on the other hand, is a type of white volcanic glass heated and puffed up to provide weightless aeration. Perlite looks a bit like Styrofoam, but it’s not.
Both of these materials are very effective, easily accessible, and affordable.
Potting Soil 101 perlite

6. Vermiculite

Vermiculite is a volcanic material too, but it’s slightly different than pumice or perlite because it can hold moisture like peat moss or coco coir. Vermiculite will work great for plants that need more moisture, like your peace lilies or ferns, but it’s not the best fit for plants that need more aeration, like orchids.

7. Sand

Sand is a cheap way to add drainage, especially for cactuses and succulents, as it helps imitate their natural environment.

8. Orchid bark

Speaking of orchids, orchid bark is a wonderful material for your epiphytic or vining plants. These are just shavings or chunks of wood, and using them as the base for potting mix helps with aeration, water flow, and the prevention of soil compaction.

These are the main additions you can use to improve store-bought potting soil. You can also enrich the soil with a handful of compost or worm castings; these will act as a slow-release fertilizer for your plants.

Craft your own potting mix blend - basic recipes

Feeling adventurous? Then we highly recommend trying to mix up your own custom soil blend for your houseplants. The first step is, of course, learning about the basic needs of the specific houseplant you’d like to re-pot. Consider the natural environment of the plant and try to imitate the soil conditions, or just read up about the plant online to know the soil it needs for sure.
Potting Soil 101 repotting plants

When you’re ready, get a big bucket or tub to hold the mix and a soil scoop or a big spoon. All you need to do is mix everything up thoroughly and use it to repot the plant. You can store any excess potting mix in an airtight container.

Here are three basic recipes to get you started:

1. Tropical plants mix - equal parts all-purpose potting mix and coco coir or orchid bark.

This pretty basic blend is rich, but well-draining. It works for a variety of tropical plants that love evenly moist soil, such as calatheas, aglaonemas, palms, ferns, and peace lilies.

2. Cactus and succulent mix - equal parts all-purpose potting mix, sand, and perlite or pumice

This super airy and porous mix is great for cacti and succulents. You can add even less potting mix if you live in a cold or very humid climate.

3. Aroid mix - equal parts coco coir, orchid bark, and pumice or perlite (optional - a handful of activated charcoal).

This is the ideal fit for monsteras, philodendrons, pothos, and other aroid plants. This mix also works great for orchids, staghorn ferns, and other epiphytic houseplants.

H/T: Wild Interiors, Harper Nurseries, GrowfullyBybrittanygoldwyn.comPistilsnursery.com

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