How have you found using peat-free compost? This article is about my experiences with it. Although I am going to keep positive, I do have to confess that my experiences are at the least “mixed”. Let’s start with some late October stunners from the garden:-
Solidago rugosa ‘Fireworks’:-
Up front I should say I am all for saving our scarce peat fields, and using greener alternatives. As manufacturers moved towards peat-free multi-purpose compost, they a) reduced the amount of peat in the product and b) upped the amount of “substitutes” for peat. There had been years of trying different other products to be a substitute for peat, and in the main what the multi-purpose composts I have tried used was coir. The fact that there was many years advance notice to manufacturers, and that they used the word “substitute” meant I have been surprised at how much trouble I have had using these products. I assumed that we now were being sold a like-for-like substitute for the peat-based multipurpose composts I had used until then. We were not told otherwise – i.e. no publicity/education/info about using the product differently from the peat-based ones was (to my knowledge) provided to us amateur gardeners.
The first thing I noticed was how very different in consistency the reduced-peat or peat-free compost was – much, much coarser. Given that I personally use multipurpose compost to sow seeds; prick out seedlings into; take cuttings; and to pot up plants/bedding/hanging baskets etc; the extreme lumpiness and length of matted fibre was a problem. At one point in 2020-21 it was almost as if old door mats had been roughly chopped into my bags of compost so huge were the fibrous lumps of material. I tried sieving – there were almost NO particles small enough to fall through a garden sieve. I found the odd stone/bit of slate in the mix.
The problem with such coarse texture is that seeds do not lay evenly on the compost – even mixing half and half with vermiculite as I used to do with the peat-based multipurpose – there are still huge air pockets in the compost, and the seed is either too deep, not in touch with the compost (and therefore will not germinate), or all falls into clumps in the crevices. (Pricking out seedlings is similar in that the small roots are not consistently in contact with the compost, and in some cases cannot force their way through the solid lumps of matted material.) I think this is still a problem generally, as when gardening programmes show you how to sow seeds they now specifically mention that you need to press the seeds down into the compost so they are in “intimate contact with the compost”, not something they used to say.
As I normally use seven 70 litre bags of multipurpose a year on sowing seeds/pricking out/potting on, trying to find enough appropriate consistency material via sieving in these circumstances was not successful. I resorted to laying a layer of vermiculite over the top of the multipurpose, pressing down, then sowing, then covering with more vermiculite. A lot more vermiculite was therefore used, at a greater cost. The only time I used “straight” peat-free compost was in potting up large plants into large pots.
Two asters shining brightly now – Aster ‘Silver Spray’ and Aster divaricatus:-
My husband having listened to my complaints, did some research into what professional growers were doing and this growing season suggested I tried using neat coir (the compressed bricks that are sold for terrariums for reptiles as it is “dust-like” in consistency. Once reconstituted with water you mix half and half with perlite. Both are inert media – i.e. they have no nutrients in them whatsoever – which is fine for seeds germinating as they don’t need nutrients for that – but they DO need nutrients to grow on.
Now as we know, seedlings are pricked out once they grow their first true leaves. So I have to say that all the seeds germinated well in this mix, but I was more stressed than normal about WHEN they had grown their first true leaves and pricking them out, as I was worried they would collapse if left until I was ready to prick them out – which might be a few days later – as they had no nutrients in their compost to keep them going. Learning point for next time, do not grow two different types of kale or chard seedlings in the same pot as you can see in the quarter trays above – they germinate at slightly different times, and in an inert medium this is a problem.
I decided to use half by volume of this mix of coir/perlite and half peat-free multipurpose to prick out the seedlings, so that they had SOME nutrients, but it helped adulterate the consistency of the multipurpose. Here are the kales pricked out at the end of April:-
Again, all the seedlings grew away well in this mix, but then after a couple of weeks they seemed to pause. The tomatoes didn’t get any bigger for example, though none of the green leafy veg got chloritic, but nothing grew away. The professional growers’ advice was that the seedlings would need a liquid general fertilizer after two weeks, and each week thereafter to grow away. I have to say, I had NEVER fed my seedlings when using multipurpose with peat in it. So I bought a general fertilizer and gave them all a feed. The tomatoes spurted up in growth suddenly, and more spindly than I expected (i.e. all stalk, not all that much leaves). I only gave the tomatoes this one feed before potting them on into their final pots. Curcubits, leaves, chillies got more feeds.
Anemone ‘Honorine Joubert’:-
Another issue that is only now becoming apparent, (and now being advised more widely to gardeners), is about watering regimes using the peat-free compost. Because I was using “neat” coir, the clear advice with it was that watering is different. It retains moisture lower in the pot and dries out on top, so if you look at the top of a pot you may think it needs watering when it doesn’t. You need to pick it up and test its weight. This is slightly more problematic if you have seedlings, as they are obviously growing in the top couple of centimetres or so of the pot to begin with. It really shouldn’t be a problem with sowing seeds as you water the medium once either before sowing, or from the bottom after sowing and then leave the pot until seedlings appear. As the peat-free multipurpose composts I have are coir-based as the “substitute” for peat, this holds true for them. However, up until now this has not been made clear to us gardeners, and I for one assumed “substitute” meant like-for-like and therefore have been watering in the same manner as for peat-based media. Clearly this has meant many people overwatered seeds/seedlings/plants, and there have been many failures.
In terms of usage for taking cuttings, normally I would mix multipurpose with vermiculite 60/40ish to open it up and provide water-retention. But based on our reading for using coir, this year I decided to just use multipurpose as it was a) coarse and b) retaining water lower in the pot. I cannot definitively say this has worked out ok as the weather was so wet this year many rotted outside in the later summer, rather than taking well. Those that were grown under cover seem to have worked as well as I would have expected from using peat-based compost and vermiculite. Here’s an outside tray of cuttings growing on well towards the end of September – these were a consolidation of 4 trays-worth of cuttings, the rest didn’t make it….:-
So to sum up, I am still not happy with the texture of the peat-free multipurpose composts, though they are getting (slightly) less coarse. I do not believe they are a like-for-like product either in terms of texture, nutrients or watering, and that this has NOT been addressed by the industry (or the gardening advice givers) in terms of education of us gardeners. I don’t consider myself a novice gardener, but I am not a professional grower either, and I have struggled with growing from seed using the peat-free multipurpose. It has put me to more expense buying extra products to achieve a similar result as using the multipurpose composts containing peat, none of which has been articulated as being required to support the peat-free multipurpose product.
Next month, a review of my veg/fruit growing this year, and some autumn colour. Let’s finish with the same plant in two different locations on almost the same day this October – Virginia Creeper, (Parthenocissus quinquefolia), firstly in the Lake District, and then in my garden:-
Sheila May
