Topic: Making your own potting compost

[Spudbash]

Hi all,

I'm finding Allotments 4 All brilliant for everything from rat management to fruit tree bargains, so a big thank-you to everyone who's posted helpful advice for the benefit of the rest of us.  ;D

I've just ordered a Scheppach hand rotary soil sifter so that I can make my own potting compost. I want to use the potting compost to grow tomatoes, cucumbers, melons and also various fruit trees (yes, I got carried away shopping!).

My garden soil is quite good - a sort of stony woodland loam, I suppose, and I've got leafmould from the two huge oak trees in the garden. I also have compost (from lawn clippings, herbaceous stuff and fruit and veg waste), and a big sack of lime; also some ancient bags of chicken manure pellets, seaweed meal and sharp sand. So I think I've got plenty of suitable ingredients.

All I need now is a recipe or two to suit what I want to grow. Any tried-and-trusted ideas out there, or any links to websites with suitable info?

I'll be really grateful...  ;D

[chriscross1966]

No chicken poo in the seed compost :D

[Spudbash]

Thanks crisscross!  ;D I should have said that I will carry on buying seed compost for sowing - not just to avoid chicken poo scorching the seedlings, but also to prevent damping off.

What I want to do is to avoid having to buy huge amounts of compost for fruit trees and veg in pots, in future. (My space is limited because there are no allotments where I live, so I'm cramming as much as I can into my garden.)

If anyone out there has any more advice, I'd love to receive it.

[Robert_Brenchley]

I used to follow the standard JI recipes (they must be out there on the net somewhere; does anyone know where?), but I substituted leafmould for peat. I'm seriously thinking of going back to rolling my own.

[Baccy Man]

The John Innes recipes amongst others are available here:
http://www.the-organic-gardener.com/making-compost.html#recomendrecipes

[Ian Pearson]

Just something to watch out for... some leaves are allelopathic (release chemicals that inhibit growth or germination). What I don't know is how long the chemicals persist. Leaf mould takes about 2 years to really form, so maybe that's long enough for them to break down, and be safe to use in seed compost

I don't know, but it might be worth trawling the internet to check.

[Robert_Brenchley]

Use deciduous leaves, which break down rapidly, and don't produce much humic acid. Pine needles rot much more slowly, and produce a much more acid soil due to the humic acid they release. They might be OK as an additive for acid-loving plants.

[Spudbash]

Thanks guys - and it does seem to be a guy thing, doesn't it?!

I think my oak leafmould will be ok, particularly as I have lots of really old, crumbly stuff.

I'll take the link, thanks, Baccy Man - couldn't find anything online when I looked, but there do seem to be mud-pie recipes a-plenty, here. And at the end of the day, it's all about mud pies, isn't it?

 ;D ;D ;D

[Ian Pearson]

I do buy some compost, but I recycle it as much as possible.
At this time of year I'm just about due to make up my mix for the busy spring period. The main ingredient is all last year's spent seed compost, and compost from any old pots, and spent compost from a neighbours window boxes, which has all been stored overwinter in a bin. I start by removing any roots and crocks, then add about half as much new compost, a couple of shovelfuls of garden soil, maybe some builders sand if any can be 'aquired', and finally a handful of organic fertiliser, and a sprinkle of ash from the wood burner. Mix well, and bag up ready for use.
Some will say it's best to use sterilised compost, but I find I get very little trouble from fungal disease, and a few weed seeds do not bother me. I also do not wash out pots or seed trays, shock-horror!
Any seedlings that die from disease are weaklings, and no good to me!

[lincsyokel2]

I do buy some compost, but I recycle it as much as possible.
At this time of year I'm just about due to make up my mix for the busy spring period. The main ingredient is all last year's spent seed compost, and compost from any old pots, and spent compost from a neighbours window boxes, which has all been stored overwinter in a bin. I start by removing any roots and crocks, then add about half as much new compost, a couple of shovelfuls of garden soil, maybe some builders sand if any can be 'aquired', and finally a handful of organic fertiliser, and a sprinkle of ash from the wood burner. Mix well, and bag up ready for use.
Some will say it's best to use sterilised compost, but I find I get very little trouble from fungal disease, and a few weed seeds do not bother me. I also do not wash out pots or seed trays, shock-horror!
Any seedlings that die from disease are weaklings, and no good to me!

The two biggest problems in making your own compost are a) knowing the pH and b) knowing the nutrient levels.

The first one you can determine with a pH testing kit, the second one is much harder to do without a lab test.

Nutrient levels are measured in the rough by the conductivity of the compost, measured in micro siemens per metre (uS/m). As a rule ,used compost is around 200, unused soil id 350. New retail compost is about 500 and professional growing media is 600+.   If you make up a home compost bin,  putting in the usual kitchen waste and garden clippings, and leave it a year, the conductivity will be about 2000 - technically is known as a conditioner, because its too 'hot' to grow anything in. You need to get the conductivity of the home mixed final product to about 600, so you need to mix it about  8 parts home made to one part compost bin conditioner.

Consistency is all when making your own, otherwise the whole thing becomes too hit and miss.

If you want to tinker with the science, heres an interesting in detail explanation of EC
http://ohioline.osu.edu/aex-fact/0565.html

[Vinlander]

If you sow seeds like toms, peppers etc. that need high temperatures then try and find a takeaway that sells food in clear microwaveable trays.

You can fill them with any recycled compost and microwave them as if it was a meal. Then it's sterile and when it's cool you can sow straight into it, put the lid on and guarantee that any damping off came from the seeds.

Some people swish the seeds in bleach solution to make sure - but I don't know the right strength (problems are very few with this method anyway).

When they emerge you can prick them out. The clear lid means it's no disaster if you're a few days late.

If you can spare the trays you can perforate the bottoms, remove the lids and leave the seedlings to grow on.

[Spudbash]

There's a lot more to this composting lark than I'd imagined. Thank you all very much for your tips.  :)

[Ian Pearson]

Most composts (growing media, to be clear) you see now nowadays call themselves 'multipurpose' meaning that they are intended for seed raising, and potting. 'Back in the old days' there was either potting compost or seed compost, with the seed compost having lower levels of nutrient, the theory being as I understand it, that this encouraged good root development. I suspect using 'mutipurpose compost' for seed raising may make the seedlings 'soft', and possibly increase problems with fungal disease.
Treat seeds mean, I say - slim pickin's nutrientwise, and plenty of bacteria, fungi and assorted microbes to toughen 'em up and deselect the weak.

Obviously it's a different matter for potting on. There needs to be enough nutrients to last for the time that the plant will be in the pot. Preferably slow-release, otherwise most of it gets washed away the first time you do a heavy watering.

[lincsyokel2]

Most composts (growing media, to be clear) you see now nowadays call themselves 'multipurpose' meaning that they are intended for seed raising, and potting. 'Back in the old days' there was either potting compost or seed compost, with the seed compost having lower levels of nutrient, the theory being as I understand it, that this encouraged good root development. I suspect using 'mutipurpose compost' for seed raising may make the seedlings 'soft', and possibly increase problems with fungal disease.
Treat seeds mean, I say - slim pickin's nutrientwise, and plenty of bacteria, fungi and assorted microbes to toughen 'em up and deselect the weak.

Obviously it's a different matter for potting on. There needs to be enough nutrients to last for the time that the plant will be in the pot. Preferably slow-release, otherwise most of it gets washed away the first time you do a heavy watering.

1. The low nutrient level in seed compost is because quiet simply any compost with an EC above about 1000 is too 'hot' for seedlings, and the massive ion flux into the root cells walls destroys the roots,  referred to as 'frying' the roots.

2. This is why professional growing media usually has either a 6 or 9 months CFR (Controlled Release Fertiliser) in it, or its watered with  a liquid feed at regular intervals. Retail compost is inferior because it has no form of nutrient control other than the nutrients  in it when you start - consequently professional growing medium is much more expensive, but then spectacularly better..

[tonybloke]

1. The low nutrient level in seed compost is because quiet simply any compost with an EC above about 1000 is too 'hot' for seedlings, and the massive ion flux into the root cells walls destroys the roots,  referred to as 'frying' the roots.

Not quite!!


seeds have in them sufficient food stores to start growth. most seeds will quite happily germinate and start growth in sterile media, such as rock-wool,  perlite, or vermiculite.

[laurieuk]

Wow :o all these technical details when I started as a boy back in the 40 s we had to make all our own composts. Gardeners would have their own mixes for different plants, We stacked turf to rot and use as the basic loam, always pulled apart so that the fibre was not riddled out. Charcoal from the bonfire, leaf soil,sharp sand etc. We used the basic JI formula which I think was 7-3 2 and various fertilisers.

[lincsyokel2]

1. The low nutrient level in seed compost is because quiet simply any compost with an EC above about 1000 is too 'hot' for seedlings, and the massive ion flux into the root cells walls destroys the roots,  referred to as 'frying' the roots.

Not quite!!


seeds have in them sufficient food stores to start growth. most seeds will quite happily germinate and start growth in sterile media, such as rock-wool,  perlite, or vermiculite.

True, but thats not the primary reason why seed compost is made with low nutrients. High levels of nutrient WILL fry seedlings, ive seen happen on an epic scale at a nursery specialising in snowdrops and violets when they were delivered the wrong compost.

By  extension, it shows you how low the nutrient levels in retail multipupose compost are by the fact you can grow seedlings in in.

[caroline7758]

. most seeds will quite happily germinate and start growth in sterile media, such as rock-wool,  perlite, or vermiculite.

I've used peat-free multipurpose mixed with perlite (roughly 2:1) for the last few years for seeds and found it pretty successful. I usually cover with vermiculite to stop the compost drying out.

[lincsyokel2]

. most seeds will quite happily germinate and start growth in sterile media, such as rock-wool,  perlite, or vermiculite.

I've used peat-free multipurpose mixed with perlite (roughly 2:1) for the last few years for seeds and found it pretty successful. I usually cover with vermiculite to stop the compost drying out.

You might also try using hydroleca  on top once they seedlings get going, as it will hold more water for its volume.

Did you know there's only two place in the world where there's perlite ore? South Africa  and China, and the chinese mine has 80% of the worlds reserves. So when it closed for 4 months in the winter and everyone started to run out of ore, the price of perlite went through the roof. Its now producing again, so hopefully the price will come down again.

[Wilder]

that explains why my last bag of perlite cost £20. I nearly dropped on the spot!

I love bits of what some idiots call "useless information". How can information be useless???