Mixing my own potting soil for ferns and leafy plants
A simple, airy potting mix I put together from three or four ingredients, and why the texture matters more than the brand.
For a long time I bought whatever bag of houseplant compost was on sale and used it for everything. It worked, more or less, but many of my plants sat in dense, wet soil for days after watering. Over the last year I have started mixing my own, and the difference in how the roots look at repotting time has been striking.
This is not complicated, and you do not need special equipment. A bucket, a trowel and a dry place to store the ingredients is enough.
Why texture matters
Roots need two things from soil: water and air. A mix that holds too much water squeezes out the air, and roots start to rot. A mix that drains too quickly leaves the plant thirsty. The goal is a loose, crumbly texture that holds moisture inside its particles but lets excess water run through the gaps.
When I squeeze a handful of freshly watered mix, I want it to hold together briefly and then crumble apart. If it stays in a tight, wet ball, it is too dense.
My basic ingredients
I keep four things in sealed containers:
- A good quality general potting compost as the base.
- Fine orchid bark, for structure and air pockets.
- Perlite, the light white granules that keep the mix open.
- Horticultural grit or coarse sand, for weight and drainage in some mixes.
The fern and leafy plant mix
For ferns, pothos, philodendrons, peace lilies and similar plants I use roughly:
- Two parts potting compost.
- One part fine bark.
- One part perlite.
I measure in old yoghurt pots, so "one part" is simply one pot. I mix everything thoroughly in a bucket and dampen it slightly with a little water before using it. Bone-dry mix repels water at first and is unpleasant to work with.
The bark is what really changed things for my ferns. It resembles the loose leaf litter where many of them grow naturally, and it keeps the mix from compacting over time.
A drier mix for succulents
For succulents and cacti I change the proportions to:
- One part potting compost.
- One part perlite.
- One part grit.
This drains very quickly. Water should run through the pot almost immediately.
Things I avoid
- Garden soil from outdoors. It compacts badly in pots and can bring in pests.
- Adding a layer of stones at the bottom of the pot. It does not improve drainage; it actually raises the level where water collects. Drainage holes and a good mix do the job instead.
- Using mix straight from a damp, open bag left outside. That is how I once brought fungus gnats home.
Storage
I keep each ingredient in a lidded plastic box in a cupboard. Dry, sealed ingredients last for ages. I mix only what I need for the day's repotting.
Is it worth it?
For one or two plants, a good bagged mix plus a handful of perlite is fine. Once you have more than a few plants, though, mixing your own is cheaper, and you can adjust it for each plant. Mostly I enjoy it. There is something calming about stirring a bucket of bark and compost on a Saturday morning with the radio on, knowing the plants will be better for it.