[A Reyt Tayty]

Does it go off? Even in unopened bags?
Any way of reviving it?

[mumofstig]

It can get wet and compacted, but I've not found it off, so to speak.

It needs fluffing up if it's compacted but always seems ok to use - if it was good in the first place 

[Aidy]

I am not sure and I have questioned this before.

I have found that a certain make of compost pretty much killed all my seedlings off.

I use Levingtons to start the seed off then transplant into a different brand, interestingly the different brand concerned has had the same effect with other plot holders, their seedlings look very good and healthy then when transplanted they die or look very sick and are slow growing.

Now i assume that like a few things in life the source will be the same for a few companies, never looked into it.

I now avoid the other brand like the plague and have so far had no problem since.

[Agatha]

How long have you had it?  The nutrients do break down over time, so if it's old stuff, it might be better to spread it on the plot as a mulch & start again.

[aelf]

I remember this story from 2008 about old compost which killed a man:

http://www.guardian.co.uk/science/2008/jun/13/medicalresearch

so take care when opening your compost!

[goodtogrow]

I too have recently used old compost, unopened, and noticed that it had degraded to a silty consistency, not chunky, or shreddy, so its structural properties were worse.  I added gravel to make it a more open medium.

Have always wondered how we know whether the nutrients are evenly spread throughout the bag, so when we fill up a small plug tray with it how much nutrient is in every cell, and is that enough?

So I also add garden compost as a slow release fertilizer.  For seed trays that may not be necessary, but for potting on it seems to guarantee nutrition.

IMHO, the liquid feed applied to multi-purpose compost is more likely to degrade over time than not.  I have been known to add extra liquid feed (Baby Bio houseplant food in weak dilution) to peat-based compost to revive it.

All of which depends on the quality in the first place, which seems to vary between manufacturers - we just don't know!

[A Reyt Tayty]

How long have you had it?  The nutrients do break down over time, so if it's old stuff, it might be better to spread it on the plot as a mulch & start again.

It's only some left over from last year. My brainwave was to put it through a fine seive, keep the fine stuff for seed compost as nutrients not critical. Then use the rest for potting on chrysanths and suchlike.

[solway cropper]

How long have you had it?  The nutrients do break down over time, so if it's old stuff, it might be better to spread it on the plot as a mulch & start again.

It's only some left over from last year. My brainwave was to put it through a fine seive, keep the fine stuff for seed compost as nutrients not critical. Then use the rest for potting on chrysanths and suchlike.

That should work OK. I've done similar with no problems. TBH I only buy commercial compost when it's on special offer and use it to bulk out my own home-made potting mix.

[New shoot]

Multi-purpose compost does degrade over time.  It essentially carries on composting and breaks down as Goodtogrow describes.  Its a slow process in a sealed bag, particularly if the bag is kept dry, but eventually it will happen.

The nutrient content will also degrade, again this will be a much faster process if the bag is wet, or not sealed. Its the nitrogen element that will go first 

[Billnorfolk]

The problem with peat free compostis some of it originates from recycling ie kitchen and garden waste and can contain weed killers from lawns etc.The main reason why some works and others dont .Compost left outside especialy in cold weather wont grow seeds if left to get cold ,store in greenhouse in the dry and warm.

[Yorkie]

The problem with peat free compostis some of it originates from recycling ie kitchen and garden waste and can contain weed killers from lawns etc.The main reason why some works and others dont .Compost left outside especialy in cold weather wont grow seeds if left to get cold ,store in greenhouse in the dry and warm.

Do you have a source for this assertion, Bill?  Would be interested to read it 

[Plot 6B]

Have you noticed that on the sides of the bag it states."Protect Fom Frost"
Does this have an effect on it's 'Shelf Life' and if it does, why do Garden Centres, etc,
keep the bags outside even in winter?

[JayG]

I think that stored dry, compost should last quite a long time, but many garden centres store it outside, and given the recent weather, allowing it to get wet must kick-start all the natural processes which will degrade its quality (not to mention the increased risk of a hernia when lifting it out of the car boot!  )

[A Reyt Tayty]

Compost left outside especialy in cold weather wont grow seeds if left to get cold ,store in greenhouse in the dry and warm.

Wouldn't bringing it in from the cold and letting it warm up make it ok for growing seeds though? Even better for sowing seed if the nutrients have lost their full potency?

[fatcat1955]

Compost left outside especialy in cold weather wont grow seeds if left to get cold ,store in greenhouse in the dry and warm.

Wouldn't bringing it in from the cold and letting it warm up make it ok for growing seeds though? Even better for sowing seed if the nutrients have lost their full potency?

Yes once it has warmed up it will be ok. i also keep the watering can in the greenhouse so that the water in it warm's up as well. Too cold water can shock your plant's.