Renewable composts - are they possible?

[Paul Cumbleton]

With the environment in mind, the RHS is striving to reduce its usage of peat and it is likely we will aim to go further and stop using peat altogether. As even John Innes compost contains peat, this means we would not be able to use what is at the moment one of the key ingredients of our composts for alpines and bulbs. I would like to know if there is any experience out there of growing alpines and bulbs in composts that could be said to be made entirely of renewable ingredients?  Is it possible? How are such composts managed? How do they perform long term? Ideally we would like to end up using composts or ingredients that are available to buy in a bag from garden centres, so that we use something that everyone can obtain (so things like leafmould that not everyone has access to would not be our first choice). Can anyone suggest candidates we should try?

If anyone has actual experience or suggestions to try or any other comments about this, I think this would be a very worthwhile area to discuss (although the phrase “can of worms” also comes to mind….!). Over to you all…

Paul

[Maggi Young]

I suppose we are using what is pretty well a "renewable" compost, Paul. We use loam, sand , gravel and composted shreddings. We have access to leafmould and do utilise that where needed, but the other ingredients can make a perfectly good compost which maintains a good structure over several years; that is, it does not break down to become either too sticky or dusty, but remains a good "texture", if you know what I mean!
The current insistence of many to move completely away from the use of peat does rather beg the question, to me, of what happens when it is decided that sand or gravel or even loam, is not sustainable for large-scale use for commercial composts?
After all, sand and gravel are not in endless supply and their extraction from the earth can cause problems too, can it not ?  
The whole area is rather fraught with inconsistency of logic, I reckon!

[Carlo]

Paul,
I remain convinced that we can grow our plants in ANYTHING so long as nutritional needs and physical support needs are met. I've always intended to experiment with broken clay pots, crumbled glass and the like to prove that it can be done. A light, regular feeding ought to account for macro- and micro nutritional needs.

[Paddy Tobin]

Would there be a use for bark, shredded and composted bark. I used shredded bark for a footpath in the garden a few years ago and found that after a few seasons it had broken down to a very fine material similar to leafmould. Presently, bark is a by-product of the timber industry and, by and large, is a waste product.

I could not comment on its use with alpine plants though I imagine the addition of grit, sand or gravel, would make it suitable. I have found it perfectly fine for some woodland plants.

Paddy

[gote]

We discussed the peat topic some years ago.
There are very large resources in Scandinavia and even larger in the baltic states and gigantic resources in Russia.
I think I remember that the conmbined peat bog area in Scandinavia is larger than Scotland and the thickness of the layer is growing all the time.
No habitat, plant or animal is in any way endangered by the mining of the peat in Scandinavia or east of us since only minute parts of the total peat bog area are suitable for commercial mining.
I cannot understand why you cannot use peat from say Estonia or Lativa. They do need the influx of currency and today they use the stuff as fuel in power stations.
Because of the cheapnes of the currency and wages in those parts of the world it would probably be much cheaper than that mined in the UK and that includes transport.
Cheers
Göte
 

[David Shaw]

As a 'no peat' person I use a basic compost of equal parts loam, grit and leaf mould. B&Q soil conditioner replaces the leaf mould when this runs out. Whilst not being one of the SRGC's 'top' growers I find it to be a satisfactory mix.
Peat? My argument is that peat itself is not the issue but the biodiversity that it supports. All the wild life (plants, insects, birds, etc) utilise the top few inches of the moss. Remove this and you lose a whole ecosystem.

[fermi de Sousa]

Hi Paul,
Most potting-mix producers in Australia abandonned peat a long time ago (probably around 20 years ago I think) and we still have a thriving nursery industry (barring water restrictions!!) which relies solely on "peatless/soilless" mixes.
I grow all my potted plants (albeit not too many alpines, but a large number of bulbs) in commercial mix which is mostly composted bark - to which I usually add some grit for better drainage.
cheers
fermi

[Paul T]

I grow all of my potted stuff in commercial potting mixes based on composted pine bark.  Almost all my little treasures you see me post on these pages (some of which at least would be classified as "alpines" I think) are in a good quality commercial mix, sometimes with sand or grit added for drainage etc.  The only other thing I sometimes use is Sphagnum moss, for certain plants such as some carnivorous and some orchids.  No peat used here as far as I know.    That said, I still do have an old compressed bale of "peat moss" from years ago I think...... dreadful stuff to re-wet if it dries out of course. 

[Tim Summers]

Hi Paul
I grow a wide range of bulbs in hammer milled pine bark which has been composted at least 6-12 months with Urea. I add 10% quartz sand and one tonne of dolomite/25 cubic metres to this and allow another 6 weeks for ph to rise. Moisture characteristics are pretty good but a problem if allowed to dry out. The bark tends to break down after 2 seasons and becomes stale, for want of a better word. The bark is also quite hungry in that Nitrogen drawdown can can be a problem unless a fairly constant dilute fertilizer regime is kept up.
I have trialed coconut husks (coir peat) also, which acts quite similar to natural peat. This is suitable for bulbs needing higher available moisture levels.
The problem as mentioned by Maggi, is that quartz sand is a limited resource here now and is extracted from riverbeds. Expanded clay beads or similar could be an alternative.
In New Zealand, commercial growers are using pine wood shavings as a medium with success. As Carlo has said, a potting mix is merely a medium for support and moisture/nutrient retention. Possibilities are great.
 
Goodluck. Tim

[gote]

We do not need quartz sand. Any sand that is not decomposited carbonate stone will do. Sand of suitable grain size is a byproduct in many places where gravel is mined for roadbuilding and other purposes. It is a question of looking in the right places. The amounts consumed by us is very small compared wioth the amounts handeled by these companies so we are not good customers. Sometimes the problem can be solved by asking to be allowed to collect some surplus from the operatins and contributing to the coffe cash box.
Cheers
Göte.
PS
If we dig peat we do destroy a habitat but east of the North Sea the destruction is less than a promille of the surface. Further. If we dig all the peat from a bog we restore the original lake and what is wrong with a lake as habitat?

[Giles]

Bark can (according to some) support/promote infection with Honey Fungus (Armillaria).

[Paul Cumbleton]

Thanks everyone for the responses so far. I agree with Maggi that this whole area is fraught with inconsistent logic. I will be meeting next week with our head of science so I can discuss what the RHS view is on the wider environmental issues, for as Maggi says, there are many ingredients such as loam, grit etc that we use that could be said to be unsustainable too. I would not want to embark down a road of learning how to manage a new type of compost only to find that in a few years time I have to give this up too. But I didn't really want to discuss the peat issue as such here, I more wanted to see what other things people have experience with.

Carlo & others commented on a compost providing mainly support and nutrition so that all kinds of things could be usable. I feel things are a bit more complex than that - a compost has to provide the right balance of aeration, moisture content, pH, etc that is suitable for the plants we grow. Finding a suitable mix could be difficult. Particularly so as I want to use ingredients available to anyone (in the UK at least). All our current composts use ingredients that anyone can go and buy at a garden centre. I feel this is important - if we were to use ingredients or professional mixes not available to amateurs, then it would be difficult to pass on our knowledge to the gardening public as it would be based on using things they cannot obtain. Several of you relate experience with composted bark and this does seem to offer possibilities - we have already tried this on a small scale trial here but we need to experiment further.

I will also be meeting with a rep from a company that produce peat-free mixes to see just what they offer and whether any would be worth trying - if they contain ingredients that anyone could copy.

Keep the experiences coming. I will report back what we eventually decide to do.

Thanks everyone

Paul

[Maggi Young]

..... as I want to use ingredients available to anyone (in the UK at least). All our current composts use ingredients that anyone can go and buy at a garden centre. I feel this is important - if we were to use ingredients or professional mixes not available to amateurs, then it would be difficult to pass on our knowledge to the gardening public as it would be based on using things they cannot obtain.

I applaud this desire, Paul. If the RHS is to be truly helpful to and supportive of, amateur gardeners, then this aspect is crucial.

[David Nicholson]

Paul, have you ever tested Green Ore Compost to see how much peat there is in it, I would be interested in the result? It doesn't look or feel a peaty compost to me.

[Paul Cumbleton]

Hi David,
The Green Ore brand of John Innes conforms to the original "true" formula for John Innes - which means it has 7 parts of loam, 3 parts of peat and 2 parts of grit (plus the fertiliser). This means it contains 25% peat. Of course this means that 75% of the mix is not peat, which is why it doesn't look or feel particularly peaty.

Cheers

Paul