How we make our own seed compost every year.

Each spring, one of our favourite garden jobs is making our own seed compost. Not only does it save money but it also gives us full control over what goes into our mix—something that’s especially important when we’re nurturing young, delicate seedlings. We use equal parts homemade compost, perlite, and coir.

Why make your own seed compost?

Seedlings are sensitive. They need a growing medium that’s light, free-draining, and low in nutrients (too much feed early on can damage young roots). Many store-bought seed composts do the job, but making our own means we know exactly what’s in it, and we can tweak it year by year depending on how it performs.

We use equal parts of the following:

Homemade compost.
We sift our well-rotted compost to remove any larger bits or uncomposted material. By spring, our compost is rich, earthy, and full of life. It’s a great base but, on its own, it’s too heavy for seeds.

Perlite.
This lightweight, volcanic rock helps aerate the mix and ensures good drainage. It keeps the compost from becoming compacted and waterlogged—two things that can quickly lead to damping off or rotted roots.

Coir (coconut fibre).
Coir adds structure and water-holding capacity. It’s a sustainable alternative to peat, and it helps keep the mix light and fluffy. We rehydrate dry coir blocks with water before mixing.

How we mix it.

We blend everything together in a wheelbarrow or large tub, breaking up any lumps and making sure the mix is even. The final texture is light and crumbly—perfect for filling seed trays or small pots.
If we’re sowing very tiny seeds, we’ll sometimes sieve the mix again or use a finer layer on top to ensure even germination.

We’ve been making this seed compost for a few years now and it’s very effective and it’s great that we are reusing our own garden waste. Every season, we tweak and adjust based on how things go, but the basic formula stays the same.

If you’ve got access to good homemade compost and are looking for a reliable, sustainable seed-starting mix, why not give this a try.