This Is Why Peat Free Composts Fail. It’s Why Understanding Peat Free Compost Is Essential When Growing Seeds & Plants.


Gardeners frequently complain about compost problems. In this article I want to explain Why Peat Free Composts Fail. And then explain how to easily overcome the problems.

Why Peat Free Composts Fail.

First we need to go back to basics. To what plants need to live and thrive. We know they need light, warmth, nutrients, oxygen, moisture and a few other things. They need the essentials when they are germinating, growing, flowering and fruiting. Only as seeds can they tolerate conditions where these essentials are restricted or absent. And that is because they are effectively in a state of suspended animation. It’s that simple!

Composts Aren’t Simple

Composts aren’t simple because the word can mean so many different things. By definition a compost is decomposed organic matter. But the gardening industry then misuses, or at least confuses, the situation by calling the bagged stuff produced to grow seeds and plants in, compost.

Bagged compost designed for seed and plant growing was a far from simple product. It had several other ingredients, beyond decomposed organic matter. It often had soil, peat, sand, fibrous material, fertiliser etc added to it so that it did its job much better.

What Seeds Need In A Compost

To grow seeds need the right temperature, moisture and oxygen level. In a few cases, such as aquatic plants, the right amount can mean very little. But our vegetables need quite a lot of oxygen, not too much moisture and the right temperature for the species. For example brassicas, lettuce, carrot and many others will germinate at much lower temperatures than the “warm” species such as tomatoes, peppers, cues, aubergine, etc.

And to get enough oxygen, and be well drained but sufficiently moist, the compost needs to be quite porous. Soil porosity is something I’ve written about previously and there’s more information via the link.

Modern Composts

There was a time when compost was made by professionals. People with an understanding of gardening and plants. Today it’s made by anyone that can get hold of large quantities of organic matter and can decompose them. Things like garden waste (often complete with pots, plastic bags etc.); food waste, from commercial kitchens and factories, domestic kitchens etc.; and assorted other sources.

The “compost” is rotted down as fast as possible (time is money), bagged up and sold to any retailer that will sell it. No effort is usually made to add amendments that will improve it.

What Goes Wrong With Composts

The composts I describe above lack any structure. As soon as they are watered they absorb lots of liquid and slump. This is because they have nothing in them to hold them open, no fibre, sand, etc to keep the structure open and porous. The result is an airless wet gooey mess that has no oxygen. Without air the seeds soon rot.

Often the seed producers get the blame for bad germination. Sometimes the compost retailer gets the blame.

The Solution to Poor Compost

The solution is simple. We need to open up the structure and allow air in. We need to do this to prevent it slumping.

And before someone tells me the compost should be good enough and they don’t expect to have to do this, I sympathise. But I didn’t produce the rubbish often sold as compost. My purpose in this article is to explain how to overcome the problem. So please don’t shoot the messenger.

How much amendment do you need to add? It depends on how bad your compost is. But it’s likely to need between 10 and 50%!

I tend to add 50% home sterilised loam to my own home produced compost because even that can be prone to slump on occasion. I’ve learnt to judge how much it needs and I can only suggest you practice with different mixes until you find what suits you.

If need be you can also add fertiliser and a wetting agent (surfactant). An organic fertiliser is ideal. Something like Vitax Q4.

Final Advice On Composts

If you buy compost and it isn’t up to standard legally you can take it back as unfit for purpose. The present poor quality of compost will not improve if buyers don’t complain to retailers.

Tag: Why Peat Free Composts Fail

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