Substrates & Growing Mediums — Definitions & Examples

Choosing the right substrate or growing medium is one of the most important — and most overlooked — parts of successful houseplant care. Whether you’re propagating cuttings, repotting your favorite plant, or starting seeds, the material your plants grow in directly impacts their health and growth. In this guide, we’ll break down popular substrates, what they’re best for, and why they matter — so you can create the perfect setup for your plants.

Aroid Mix

A chunky, well-draining soil mix designed for tropical plants in the aroid family like Monstera, Philodendron, and Pothos. A typical aroid mix includes bark, perlite, coco coir, and charcoal to mimic their natural growing conditions where roots need airflow and moisture without staying soggy.

Bark

Chopped or shredded pieces of tree bark, usually from fir or pine, used to add drainage and texture to soil mixes. Bark creates air pockets that prevent compaction.
 → Common in orchid, aroid, or houseplant mixes.

Cactus Mix

A gritty, sandy soil mix formulated for succulents, cacti, and desert plants. It drains quickly and reduces moisture retention to prevent root rot in drought-tolerant plants.
 → Great for Snake Plants, Aloe Vera, and Echeveria.

Charcoal

Often horticultural or activated charcoal, used in small amounts in soil mixes to improve drainage, absorb impurities, and prevent odors or bacteria. Charcoal is especially popular in terrariums or mixed into aroid or orchid soils.

Coco Coir

A sustainable, lightweight peat alternative made from coconut husks. Coco coir holds moisture well while providing good drainage and aeration.
 → Often used in seed starting or as part of aroid mixes.

Decorative Moss

Preserved moss (not living) used on top of soil for visual appeal, moisture retention, and reducing soil splash when watering.
 → Seen in potted plants or as a finishing touch in decorative planters.

Expanded Clay (LECA)

Lightweight Expanded Clay Aggregate — small clay pebbles that wick moisture and allow excellent airflow around roots. Used in semi-hydroponic growing or propagation setups.
 → Common for Pothos, Philodendron, and Hoyas in water culture.

Lava Rock

Porous volcanic rock pieces that provide excellent drainage and aeration. Lava rock can be mixed into soil or used alone for cacti, succulents, or bonsai. It holds moisture without waterlogging the roots.

Moss Pole

A support structure wrapped in sphagnum moss or coco coir used for climbing plants like Monstera or Philodendron. Moss poles encourage vertical growth and aerial roots attachment.

Orchid Mix

A chunky, fast-draining growing medium for orchids, typically containing large bark pieces, perlite, charcoal, and sometimes moss. Allows for airflow around delicate orchid roots.
 → Great for orchids, hoyas, or other epiphytic plants.

Peat Moss

A moisture-retentive organic material harvested from peat bogs. Peat moss is lightweight, acidic, and commonly used in seed starting or soil mixes, although it's less sustainable than coco coir.

Perlite

A lightweight, white volcanic glass that expands when heated. Perlite improves drainage and aeration in soil mixes and can be used alone for propagation.
 → Found in almost all commercial houseplant soils.

Pumice

A porous volcanic rock similar to perlite but heavier, which means it doesn’t float to the top of soil mixes. Pumice aids drainage, prevents compaction, and is commonly used with succulents or cacti.

Sand

Coarse, sharp sand is sometimes added to soil to improve drainage and weight. It helps replicate arid growing conditions for succulents and desert plants. Not all sands are suitable — horticultural sand is preferred over beach sand.

Seed Starting Mix

A fine, lightweight, sterile soil blend designed to support seed germination. It often includes peat moss or coco coir, perlite, and vermiculite. It holds moisture while allowing delicate roots to grow freely.

Soil

The general growing medium made of organic matter, minerals, and microorganisms. Potting soil varies widely in texture and composition depending on the plant's needs. Most store-bought houseplant soil is suitable for tropicals with minor amendments.

Sphagnum Moss

Living or dried moss that retains moisture extremely well. Often used in moss poles, propagation, or as a soil amendment for tropical plants needing humidity.
 → Excellent for rooting Monstera or Philodendron nodes.

Vermiculite

A mineral that expands when heated. Vermiculite holds moisture and nutrients, making it useful for seed starting or plants that like more consistent moisture. Often mixed with soil or used alone for germination.

Water

Water alone can serve as a growing medium for propagation. Many houseplants like Pothos, Philodendrons, and Monstera can root in water before being transitioned to soil. Clean water helps prevent rot, and roots grow visibly, making it ideal for beginners.

Every plant and every home environment is different — and there’s no one-size-fits-all soil mix. The fun part is experimenting, learning, and adjusting based on your plant’s needs. By understanding different substrates and growing mediums, you can create custom mixes or choose the right tools to help your plants thrive. Whether you’re mixing chunky aroid soil for your Monstera or popping a pothos cutting in water, your plants (and their roots) will thank you.