Recipes for Houseplant Health: Soil Substrates and Potting Mixes

For healthy houseplants, start at the roots. Hidden deep in your houseplants' soil is a secret world filled with a magic all its own, like a blanket of life for roots to settle into. 

Plant parents and collectors have long experimented with and perfected mixtures and ratios for their soil. Much like a grandmother's sacred cookie recipe, soil mixes are altered ever so slightly and then shared with the ones you love. That is precisely what we are here to share with you: a list of soil ingredients and carefully crafted soil recipes for your beloved houseplants.

The Dirt on Potting Mix & Potting Soil

Why is it so hard to buy a bag of dirt?

Packaging can be misleading, confusing, and vague when it comes to choosing the right substrate. Let’s talk about what makes a good potting mix and what to look for so you get the best bag for your plants at home.

Commonly listed ingredients of potting mix include peat moss, worm castings, perlite and vermiculite. Other ingredients might be added in such as fertilizer and natural soil amendment materials.

A good potting mix will be fluffy to prevent compaction and sterile to prevent unwanted pest problems. Look for potting mixes with a balance of moisture absorbing material and airspace. Be sure to avoid bags that list "soil" as an ingredient (these are not for indoor use), bags that don’t list any ingredients at all, and bags that have any harmful synthetics listed.

The Ingredient List

• Pumice: Naturally occurring volcanic rock formed from cooling lava that traps gas bubbles and produces a lightweight material. In potting soil pumice is used for aeration as well as to alleviate soil compaction. Pumice allows spaces for air in the soil so water and nutrients can move more freely throughout.
• Orchid Bark: Small pieces of bark used to improve drainage and moisture retention in the soil. Often made of Fir or Pine and sometimes with added soil retaining material such as peat moss.
• Peat Moss / Sphagnum Moss: Peat moss is formed from decomposing matter in peat bogs and creates a fibrous material useful in moisture retention. Most commonly used for new developing roots. Sphagnum moss is a large class of mosses that are still living and are used in kokedama creation and other aroid mounting practices. Sphagnum moss acts as a living sponge.
• Activated Charcoal: Heat treated charcoal that creates a porous material ideal for absorbing excess moisture and protecting roots from bacterial and fungal growth in the soil. Highly recommended for direct potting into containers without drainage holes.
• Vermiculite / Perlite: Both vermiculite and perlite are small volcanic minerals used for aeration in soil. However, perlite results in quicker drainage, while vermiculite results in higher moisture retention.

Craft Your Own! Common Soil Recipes

Before getting started making your own soil mix, it's important to start by identifying your plant and understanding its basic needs.

A healthy and happy houseplant begins with a strong root system, which is in turn supported by the right soil mixture. Consider what type of roots your plants have, where are they from and what supports their new growth. Is it very wet where they are from or sandy and dry? Do the plants climb up trees, or creep along the forest floor? Do they live in the rainforest, or thrive in the desert?

Now that you've got the basics covered, here are a few recipes to start with!

Cactus /  Succulent mix

Use for arid plants such as Euphorbia, Crassula, Aloe, Opuntia etc.

• 1 part organic potting mix
• 1 part pumice

Aroid mix

Use for tropicals in the Araceae family such as Anthurium, Monstera and Philodendron species

• 1 part organic potting mix
• 1 part orchid bark
• 1 part perlite
• 1/2 part activated charcoal

Tropical Mix

Use for terrestrial tropicals such as Begonia, Strelitzia, ferns, palms, etc.

• 3 parts organic potting mix
• 1 part vermiculite

Carnivore Mix

Use for bog-dwelling carnivorous plants such as Nepenthes, Sarracenia, Dionaea etc.

• 3 parts peat moss
• 1 part perlite

Prayer Plant Mix

Use for members of the Marantaceae family such as Maranta, Calathea, Ctenanthe etc.

• 2 parts peat moss
• 1 part potting mix
• 1 part perlite

We can learn a lot from our houseplants if we listen to them: they teach us through the way they live and how they grow. Experimentation is encouraged and knowledge is shared in the large and loving plant community. We'd be delighted if you share with us your recipes, your successes, your failures, and your stories. This way we can all grow a little more green with love.

By: Bee Oxford