Soil & potting mix
Best soil for Merrill's Wax Plant (Hoya merrillii)
Also called Merrill's wax plant, Merrill's hoya, Philippine wax plant.
More about merrill's wax plant
About Merrill's Wax Plant
Hoya merrillii · also called Merrill's wax plant, Merrill's hoya · tropical
Hoya merrillii is a rare epiphytic vine native to the Philippines, first discovered in humid lowland forests on Mindoro Island, and named in honour of American botanist Elmer Drew Merrill who extensively documented Philippine flora. It is prized for its compact umbels of up to 25 small, star-shaped, golden-yellow flowers with red-orange centres that emit a sweet, honey-and-caramel fragrance most intense in the evenings. The most important care point is to provide warm temperatures with high humidity and avoid cold draughts, as it cannot tolerate temperatures below 15°C for any length of time. The ASPCA lists the Hoya genus as non-toxic to cats and dogs.
Preferred mix: Well-draining epiphytic mix
Why merrill's wax plant needs this mix
Merrill's Wax Plant drinks mostly through its central cup, not its roots — so it wants a light, open, fast-draining bark mix and only a shallow pot.
- Merrill's Wax Plant is an epiphyte: its small root system mainly clings on, while the rosette "tank" does the drinking — so the mix only needs to anchor it and breathe.
- An open bark mix lets the few roots get air and dries fast, mimicking the tree-fork or rock crevice it grows in naturally.
- Because the cup feeds it, a soggy root zone gives no benefit and only invites base rot.
For the full picture on what makes up a good mix, see our guide to the main types of soil and potting media — it explains why each ingredient above behaves the way it does.
What goes wrong with the wrong mix
The wrong soil is one of the most common reasons merrill's wax plant struggles, and the damage often shows up weeks later as a watering problem. For this species specifically:
- Dense, water-holding compost rots merrill's wax plant at the base where the leaves meet the soil — the rosette can look fine while the crown is already failing.
- A deep pot full of mix stays wet in the middle long after the surface dries; bromeliad roots are too shallow to ever use it.
- Garden topsoil compacts and starves the few roots of air.
Potting merrill's wax plant deep in ordinary compost as if the roots do the feeding. Use a shallow pot of open bark mix and keep the soil only barely moist.
pH — does it matter for merrill's wax plant?
Merrill's Wax Plant likes a slightly acidic mix (around pH 5.0-6.0), which a bark-based blend gives naturally. Cup-water quality matters more than soil pH — use rain or filtered water.
If you want to check or adjust it, the soil pH guide walks through testing and the safe ways to nudge a mix more acidic or more alkaline.
DIY mix vs a bagged one
A bagged epiphytic or orchid mix works well for merrill's wax plant with a little extra perlite. The DIY ratio above is easy and cheap if you already keep orchids.
Drainage and the pot
A shallow, well-drained pot is ideal — the rootball should never sit in water. Keep the central cup topped up instead; that is how the plant actually drinks.
Merrill's Wax Plant rarely needs repotting — it flowers once then produces pups. Move pups to fresh bark mix; bark breakdown is slow enough that the parent rarely needs it. When the time comes, our repotting guide for merrill's wax plant covers the timing and technique step by step.
Merrill's Wax Plant soil — frequently asked questions
What is the best soil mix for merrill's wax plant?
2 parts orchid bark or coarse epiphytic mix : 1 part perlite : 1 part peat-free compost. Merrill's Wax Plant is an epiphyte: its small root system mainly clings on, while the rosette "tank" does the drinking — so the mix only needs to anchor it and breathe.
Can I use normal potting soil for merrill's wax plant?
Dense, water-holding compost rots merrill's wax plant at the base where the leaves meet the soil — the rosette can look fine while the crown is already failing. A bagged epiphytic or orchid mix works well for merrill's wax plant with a little extra perlite. The DIY ratio above is easy and cheap if you already keep orchids.
Does merrill's wax plant need a special pH?
Merrill's Wax Plant likes a slightly acidic mix (around pH 5.0-6.0), which a bark-based blend gives naturally. Cup-water quality matters more than soil pH — use rain or filtered water.
Should I buy a bagged mix or make my own for merrill's wax plant?
A bagged epiphytic or orchid mix works well for merrill's wax plant with a little extra perlite. The DIY ratio above is easy and cheap if you already keep orchids.
How often should I refresh the soil for merrill's wax plant?
Merrill's Wax Plant rarely needs repotting — it flowers once then produces pups. Move pups to fresh bark mix; bark breakdown is slow enough that the parent rarely needs it. A shallow, well-drained pot is ideal — the rootball should never sit in water. Keep the central cup topped up instead; that is how the plant actually drinks.
Keep reading
- Merrill's Wax Plant care — the full brief (light, water, humidity, problems, pet safety)
- How often to water merrill's wax plant — the schedule the mix feeds into
- Repotting merrill's wax plant — when and how to refresh the mix
- Soil pH guide — test it and adjust it safely
- Root rot — how the wrong soil starts it, and how to save the plant
- Overwatered plant — signs and recovery
- Why is my plant wilting? Wet vs dry diagnosis
- Best soil for purple wreath
- Best soil for snake vine
- Best soil for bracted lipstick plant
- All 10153 soil and potting-mix guides in the Growli library