Potting & Soil Mixes

Aroid Soil Mix: What It Is and How to Mix Your Own

Scroll for more →

An aroid soil mix gives climbing houseplants the chunky, airy root zone they evolved for. This guide explains what an aroid mix is, what goes into it, how to mix a batch, and how to adjust the ratio for your plants and your home.

• An aroid soil mix is a fast-draining blend for aroids: the plant family that includes monstera, pothos, philodendron, anthurium, alocasia and syngonium. Instead of plain potting soil, it combines a moisture-holding base with bark and a mineral material such as perlite or pumice, so water passes through quickly and air stays around the roots.
• Most aroids grow as climbers in the wild, with roots gripping tree bark rather than sitting in dense ground soil. A chunky mix copies that structure. A dense mix does not, and it is the usual reason an aroid stays too wet and starts to rot.
• You can buy an aroid mix ready-made or blend one from three or four ingredients. Both routes work; the texture matters more than any single brand.

What counts as an aroid

• Aroid is the common name for plants in the family Araceae. The group includes many of the most popular indoor houseplants: monstera, pothos, philodendron, anthurium, alocasia and syngonium.
• What these plants share, for potting purposes, is how they grow. Many of them, including monstera and philodendron, are what botanists call hemiepiphytes: they begin life near the ground but spend much of it climbing, with roots that attach to tree bark and take moisture and oxygen from the air. The Royal Botanic Gardens lists monstera as a climbing shrub with aerial roots, and the Missouri Botanical Garden records it climbing to around 70 feet in its native Central America.
• That growing habit is why the family is grouped together for soil. The roots want air, fast drainage, and a substrate that does not stay soggy. A mix that suits a monstera generally suits a philodendron or a pothos, with small adjustments for how chunky each plant likes it.

Why aroids need a chunky mix

• Roots need oxygen. In a dense, wet soil, water fills the spaces between particles and pushes air out. Aroid roots are not built to sit in that for long, and prolonged wet conditions are the leading cause of root rot in these plants.
• A chunky mix keeps some of those spaces open. Bark, perlite and pumice create pockets that hold air even after watering, so the roots can breathe while the mix slowly releases moisture.
• It also drains. When water moves through the pot quickly instead of pooling, the roots dry out between waterings, which is closer to how aroids experience rain on a tree in the wild.

An aroid mix is not the same as potting soil

• Garden centres sell three different things that all look like dirt, and the difference matters. Garden soil is real topsoil, heavy and often full of clay. Potting soil is usually a mix built for outdoor containers and can still be dense. A soilless potting mix is the light, peat- or coir-based product meant for indoor pots.
• University of Maryland Extension is blunt about it: products sold as "potting soil" are usually too dense to allow proper aeration on their own, and need perlite or vermiculite worked in to loosen them. That advice is exactly what an aroid mix does up front.
• An aroid mix is a soilless mix pushed further toward air and drainage. It starts from a light base, then adds enough bark and mineral material that the finished blend is visibly chunky rather than smooth.

What goes into an aroid soil mix

An aroid mix is easiest to understand as three jobs: hold some moisture, create air space, and add structure. Most recipes fill each job with one ingredient.

The moisture-holding base

• A base such as potting mix, compost or coco coir holds water and nutrients so the mix is not bone dry seconds after watering. It is the part that keeps an aroid from needing water every day.
• Coco coir is a common choice. University of Florida research on nursery substrates found coconut fibre held more water per unit of dry weight than pine bark, Florida peat, or a prepared mix, which makes it a strong moisture-holding base that still drains.
• Peat-based mixes work too, but peat is naturally acidic, with a pH around 3.0 to 4.0 when pure, and it can turn water-repellent once it dries out completely. Washington State University notes that a peat-based mix is harder to re-wet after it dries, which is why moistening the mix before repotting matters.

The air and drainage material

• Perlite and pumice are the usual mineral additions. Both are lightweight and inert, meaning they add no nutrients.
• Perlite is made by heating crushed volcanic rock until it pops. Purdue Extension describes the ore expanding four to twenty times its original volume in a furnace, and University of Arkansas Extension explains that the finished granules are closed cells that do not absorb water. That is the point: perlite creates drainage and aeration rather than holding moisture. It is also light enough to float to the surface over time.
• Pumice is a heavier volcanic rock. It does not float or wash out as readily as perlite, so it holds its place in the mix longer. Either one works; the choice is mostly about cost and how long you want the structure to last.

The structural ingredient

• Orchid bark or pine bark chips give the mix its chunky structure. Bark does two things: it creates the large air pockets that soil alone cannot, and it breaks down slowly.
• This is the ingredient that most separates an aroid mix from ordinary potting soil. It is also why orchid mixes, which are bark-heavy by design, suit aroids so well. University of Maryland's orchid guidance calls for a porous, lumpy material that does not hold water long, and notes that orchids and anthuriums are epiphytes whose roots rot in ordinary potting mix.

Optional additions

• Horticultural charcoal is sometimes added for a bit more chunky aeration. Its other claimed benefits are debated, so treat it as optional.
• Worm castings or a small amount of compost can add nutrients, which is useful in a mix that is mostly bark and mineral material.

A simple aroid mix recipe

• A reliable starting point is equal parts by volume: one part moisture-holding base, one part orchid bark, and one part perlite or pumice.
• Mix them until the bark and mineral pieces are spread evenly through the base rather than clumped in one spot. The finished mix should look chunky, not smooth.

Aroid mix ratios by plant type

The 1:1:1 mix is a default, not a rule. A few common aroid groups do slightly better with an adjusted blend.

Scroll for more →

• If you keep just one mix on hand, the 1:1:1 blend covers all of these reasonably well. The adjustments above are refinements, not requirements.

How to mix your aroid soil mix

1. Measure your parts by volume using the same container for each ingredient, so the ratio stays consistent.
2. Put the base in a large tub or bucket first.
3. Fold in the bark, breaking up any compressed clumps by hand.
4. Add the perlite or pumice last, then turn the mix over until everything is evenly blended.
5. Moisten the mix before potting. Both Penn State Extension and Washington State University recommend wetting a soilless mix first so it absorbs water evenly, because a dry peat-heavy mix repels water and is hard to wet once it is in the pot.

• A batch will keep for months in a covered bin. Keep it barely damp, not wet, so it does not grow mould or algae. If a stored mix has dried out, add water and turn it over a day before you use it.

Buying an aroid mix instead

• If you would rather not source three ingredients separately, a bagged chunky mix sold for monstera and similar plants saves the step. The trait to look for is the same one you would build into a homemade batch: a visibly chunky texture with real bark pieces rather than a fine, soil-heavy mix.
• A blend made for monstera, such as monstera potting mix, works for other aroids too, since they share the same root needs. If you are mixing for a single climbing plant, that page covers the species-specific recipe in more detail.

Drainage and pot pairing

• A chunky mix only works if excess water can leave the pot. Penn State Extension treats a drainage hole as necessary to stop the mix becoming waterlogged, and Clemson Extension advises against putting gravel or clay shards in the bottom of the pot, because a gravel layer actually slows water movement rather than improving it.
• Pot material changes how fast the mix dries. Unglazed terracotta is porous and pulls some moisture out through the walls, so plants in terracotta often need watering sooner than the same plant in a plastic or glazed pot.

Watering and fertilizing on a chunky mix

• A chunky mix dries faster than dense soil, so watering should follow the mix rather than the calendar. The Missouri Botanical Garden's guide to monstera as a houseplant suggests letting the soil dry somewhat between waterings, and slowing down further in the darker months. Check moisture a couple of inches down, or lift the pot to judge its weight.
• Feeding matters more in a bark-heavy mix. Bark and perlite hold few nutrients, so a chunky mix relies on you to supply them. Feed at a normal dilution during active growth, and ease off in winter. Some peat-based mixes include slow-release fertilizer, in which case start lighter.

Growing aroids without soil

• Aroids also do well in leca and other semi-hydroponic systems, because their roots already tolerate growing on bark with air contact. In these setups the roots sit in a reservoir of water and nutrients instead of a chunky mix.
• Moving an established plant from soil to leca is usually done gradually. The plant needs to grow a new set of roots adapted to the wetter conditions, and a sudden switch can shock it.

Signs your aroid mix is not working

• The mix still feels damp several days after watering. This usually means it is too dense or holds too much water, and could use more bark and perlite at the next repot.
• Roots are dark, soft and mushy. Healthy aroid roots are firm and light colored. Mushy roots point to a mix that has stayed wet too long.
• The mix dries out within a day or two and the plant wilts between waterings. This is the opposite problem: the mix is too chunky for your conditions, and a little more base would help it hold water longer.
• Water runs straight through without wetting the mix. Peat-based mixes can become water-repellent when they dry out completely. Soaking the pot from the bottom, or repotting into fresh mix, usually fixes it.

Common aroid mix mistakes

• Using garden soil or a heavy potting soil on its own. It compacts, holds water, and starves the roots of air.
• Skipping the bark and using only soil and perlite. This loses the large air pockets bark provides, and the mix settles into something denser than intended.
• Overpotting. A pot that is far too large holds more mix than the roots can draw water from, so the middle stays wet even in a good recipe.
• Packing the mix down hard. Firm it gently so air spaces remain, rather than pressing it into a solid mass.
• Watering on a fixed schedule. A chunky mix dries at different speeds in different rooms and seasons.

Repotting into fresh aroid mix

• Aroids generally benefit from fresh mix every one to two years, or sooner if the mix has compacted and drains slowly. Both Clemson and Penn State suggest repotting in spring or early summer, while the plant is actively growing, and moving up only an inch or two in pot size at a time.
• When repotting, loosen the old root ball and remove as much of the spent mix as you can without pulling at the roots. Trim any soft or rotten roots with a clean tool, then pot into fresh mix at a ratio that suits your watering habits. Water to settle the mix, then let it dry before watering again.