The Wrong-Soil Report 2026: what houseplants really need to grow in

Most houseplants need free-draining soil — in Growli’s 2026 analysis, 77% of 10,153 catalogued species were specified to need free-draining or well-drained soil. Standard multipurpose compost works for about 59% of plants, ideally with a handful of perlite added for drainage. The rest need a specialist medium: succulents and cacti want a gritty, fast-draining mix; aroids and orchids want a chunky, bark-based mix; and a small group of acid-lovers need ericaceous compost.

No — only about 59% of houseplants are genuinely happy in standard multipurpose compost, and even those often prefer it cut with perlite for drainage. More than a third of species (35%) need a specialist medium instead: a gritty cactus/succulent mix, a chunky aroid or orchid bark mix, or ericaceous compost. Potting a succulent or an orchid in dense compost holds water against the roots and causes root rot — the same failure as overwatering.

Dense, water-retentive compost stays wet for too long, starving roots of oxygen and letting rot-causing fungi take hold. This is why the wrong soil produces exactly the same symptoms as overwatering — yellowing, drooping, mushy stems — even when you water correctly. Free-draining soil lets excess water escape and air back into the root zone between waterings, which is why 77% of catalogued plants call for it.

Succulents and cacti need a gritty, fast-draining mix — in the catalogue, 17.6% of all species (and nearly every succulent) require one. Use a purpose-made cactus/succulent compost, or cut standard compost 1:1 with coarse grit, perlite or pumice. The goal is a medium that drains almost immediately and never stays soggy, because desert plants rot quickly in moisture-holding soil.

Aroids (monstera, philodendron, pothos), orchids and other epiphytes need a chunky, open, bark-based mix rather than soil — 15% of catalogued species fall in this group. Their roots evolved to grip bark and take air from around them, so a coarse mix of orchid bark, perlite and some compost keeps them aerated. Packed into dense compost, the roots suffocate and rot.

For most houseplants, yes. Because 77% of catalogued species need free-draining soil and standard bagged compost tends to compact and hold water, adding 20–30% perlite, grit or bark to multipurpose compost improves drainage and airflow for the majority of plants. Succulents need even more — up to half the mix as grit. The main exceptions are moisture-loving ferns and calatheas, which want more water held near the roots.

Very few. Only about 0.7% of catalogued species are true acid-lovers that need ericaceous (lime-free) compost — plants such as azaleas, camellias and blueberries. The vast majority of houseplants are happy in a normal, slightly acidic to neutral mix and do not need ericaceous compost. Using ericaceous soil for a plant that does not need it can actually cause nutrient problems.

Growli classified the structured, source-checked soil guidance for all 10,153 catalogued plant species using orthogonal, keyword-based flags — free-draining, gritty cactus/succulent, chunky aroid/orchid, moisture-retentive, ericaceous and bog/aquatic — then assigned each species a primary growing medium by most-specific match. Because soil guidance is descriptive rather than a single number, these are classifications of that guidance, not laboratory measurements. The full classification is published as a free CC-BY download so the figures are reproducible.