Best soil for monstera: a mix your roots can breathe in

Think of me as a climber. In the wild I start on the forest floor and then climb up trees, holding on with my aerial roots, according to the NC State Extension Gardener Plant Toolbox and the New York Botanical Garden. My roots like moisture, and they also need to breathe.

Every trusted source we checked asks for the same thing in different words. Penn State Extension suggests a well-draining soilless potting mix rich in organic matter. UConn's Home and Garden Education Center asks for a well-draining mix with lots of organic matter, and NYBG calls quick-draining soil essential. The Royal Horticultural Society wants an open, well-drained mix and warns that roots rot easily in compost that drains poorly.

Why does air matter so much? Roots take in oxygen from the small air pockets in the mix. UW-Madison Extension explains that perlite keeps those pockets open, and that roots suffer when the mix stays waterlogged. A good mix lets water run through and air follow, while holding enough moisture between waterings, as Clemson Extension puts it.

Aroids are the arum plants, botanical name Araceae, and the ASPCA lists the monstera among them. No extension service or botanical garden we checked defines an "aroid mix", so what goes into a bag with that label is up to each brand.

You don't need a product with that label. Any mix that drains fast, stays airy and holds some moisture does the job. If you like the chunky style, Clemson's equal parts of fir bark, peat and perlite is a published version you can trust.

Garden soil works in the ground and fails in a pot. Iowa State Extension says it loses most of its air pockets and packs down once it's in a container. Clemson Extension notes it carries too many bacteria for container plants, and Penn State Extension's repotting guide warns it can bring disease and pest problems indoors.

What about the bags on the shelf? The University of Maryland Extension suggests a soilless mix of peat moss, vermiculite and perlite, and says products labeled "potting soil" are often too dense for good air flow. Penn State's monstera page agrees on a soilless potting mix. Read the bag: if the mix feels heavy and fine, mix in bark or perlite.

Two more things that make even a good mix act soggy:

• A pot that's too big. The RHS says to go only a few centimeters bigger, because extra mix stays wet too long and risks root rot. UConn adds that a monstera handles being snug in its pot much better than being overpotted.
• Water sitting in the saucer. The RHS, UConn and NYBG all say to tip it out. NYBG suggests checking back about 15 minutes after watering.

Our repotting guide covers pots, drainage holes and the gravel myth.

NC State Extension and Penn State Extension both list a neutral pH of 6.0 to 8.0 for monstera. The RHS asks for a slightly acidic mix, pH 5 to 6, which is why its recipe uses lime-free (ericaceous) compost.

You don't need to test your mix to grow a healthy monstera. If your tap water is hard, the RHS suggests watering with rainwater or filtered water at room temperature when you can, since hard tap water is alkaline.

Signs the mix holds too much water:

• Leaves "sweat." UW-Madison Extension says leaves release droplets when the mix is too moist, and to water less to prevent root rot.
• Lots of yellow, dropping leaves. NYBG links this to overwatering or underfeeding. One old leaf yellowing now and then is normal; the care card covers yellow leaves in full.
• Soft, brown or black roots. UConn describes rotten roots as brown or black, mushy and easy to pull away. Clemson's philodendron, pothos and monstera factsheet says root rot usually comes from a mix that drains slowly or from watering too often. Our root rot guide walks through the rescue.
• The plant collapses. The RHS warns that waterlogged, poorly draining compost can rot the roots and make the plant collapse.

Signs the mix or pot no longer works:

• It dries out very fast. Penn State Extension lists a mix that dries out quickly, even in cool weather, as a sign the plant needs repotting.
• A white crust on top. UW-Madison Extension says salts build up on the surface when water can't drain through and out the bottom.

The RHS says a monstera can usually stay in its original pot for a year or two, then needs repotting every few years. NYBG and UConn both say to wait until roots come out of the drainage hole or fill the pot, then go up only one size. NC State suggests spring, so in practice that's when new growth picks up.

Fresh mix matters even when the pot size stays the same. Iowa State Extension notes that the organic parts of a mix, such as peat, bark and compost, slowly break down over the years, while perlite barely changes.

For a monstera that's already as big as you can handle, NYBG suggests replacing the top layer of soil every other year instead of repotting. You'll find the step-by-step in our repotting guide, and repotting day is also a good time to add or extend a moss pole. Taking cuttings while you're at it? The propagation guide covers what to root them in.

Wear gloves when you repot. The RHS calls the plant a skin and eye irritant, and Penn State Extension says the sap can cause dermatitis. The ASPCA lists monstera as toxic to cats and dogs, so sweep up dropped leaves and stem pieces before pets find them.