[chrisnchris]

Hi all, we have grown a few things in tubs this year, beans, toms, chilli as well a flowering plants.
I will empty the pots & protect them over winter.
What should I do with the compost, it's almost 100% bought multi-purpose.

Is there a way of re-introducing nutrients that would have been lost during this year's growing season.
I have space for something like a builder's "bulk bag" to put the used compost in, or perhaps keep for next year & add growmore to it before planting anything.
Also, what about disease, some of the toms had blight, would I be asking for trouble.
Thanks

[goodtogrow]

That's a great post of yours, chrisnchris.

Yes, IMO, you'd be asking for trouble using the spent compost again with members of the solanacea (sp?) family, toms, chilis, aubergines, peppers and potatoes.

But your thinking is still sound, IMO.  I'd mix it 50/50 with garden compost and gravel and use it as a potting mix for all but members of the solanacea family.

Best wishes
Tom

[JayG]

In theory, blight spores only overwinter on living plant material, but there are other pathogens you may be harbouring in your used compost - botrytis is another fungus you can well do without!

I wouldn't recommend used compost for any seed raising because it will no longer be sterile and would almost certainly lead to problems; damping off in particular.

Again in theory, you should be able to replace the nutrients with various fertilisers, but I must confess I have yet to find the recipe for success when I've tried it - results have generally been poor.

My spent compost now gets chucked on the garden as a general soil improving mulch, taking reasonable care to avoid using compost used for growing potatoes or tomatoes on next year's spuds, toms and related crops "just in case."

[mumofstig]

You can grow some decent carrots in it - just add some BF&B or growmore to it - and Bob's yer uncle 

DD. grows radish in his
http://chat.allotment-garden.org/index.php?topic=3309.msg36790#msg36790

[DIGGER]

What I do is technically wrong,but I do it and do not have any problems. I save all my old used container compost,in spring I mix it with home made compost . I then use the mix as a base  and top up containers with purchased compost and plant my tomato plants in it. I then feed  with home made nettle feed.
Monty Dom would be horrified,but I dont have his bank account.

[chrisnchris]

You can grow some decent carrots in it - just add some BF&B or growmore to it - and Bob's yer uncle 

DD. grows radish in his
http://chat.allotment-garden.org/index.php?topic=3309.msg36790#msg36790

Thanks Mum, I've never grown carrots so might give this a try. Can I grow them in a container or raised bed, say 2' squ X 12" deep ?

[Totty]

The medium your plants grow in is the single most important thing when growing veg. If you try to make do, or cut corners, your results will suffer. For some this is not a problem, but if you like your plants to grow as well as poss you need to give them somewhere good to live.
 For things like tomatoes, peppers, potatoes etc.. If your growing them in pots it really does pay to use sterile, fresh, nutrient rich compost.
But, carrots for example will grow nicely, as will lettuces, in pots of spent compost although they will need an occasional feed.
My preference is the same as JayG, throw it on your veg beds outside as a mulch and it will improve your soil structure no end.

Totty

[goodtogrow]

You're turning my world upside down with your observation about blight spores, JayG!  If in theory they only overwinter on living plant tissue does that mean that in practice they live on dead plant tissue, in the soil, etc??

I think the thing about re-using peat-based composts is that old peat degrades into a silt-like structure, much less aerated than fresh peat, so that even if we add nutrients as a medium it is poor.  Anyone who's bought old-stock compost, knocked out cheap at the beginning of the season, will know what I mean.  So that's why I cut it hard with aerating materials.

Agree that seed compost I've bought comes in sealed bags, and is assumed to be sterile, but MPC?  MPC bags have holes in them, don't they?  Can it then be sterile?

[JayG]

You're turning my world upside down with your observation about blight spores, JayG!  If in theory they only overwinter on living plant tissue does that mean that in practice they live on dead plant tissue, in the soil, etc??

Assuming that rotten potatoes are more dead than alive, the following extract appears to contradict the usual belief that blight can only overwinter in live plant material:

The pathogen overwinters in rotten potatoes left in the ground or by the sides of fields. However, the great majority of infections in gardens arise from wind-blown sporangia originating in other gardens, allotments and commercial crops. In the UK, outbreaks may occur from June onwards, usually earliest in the South West.

The fungus can also produce resting spores (oospores) in the plant tissues that can contaminate the soil. Little is known about their survival and their potential as a source of the disease. The investigations into oospores are continuing and more information may be available in a few years.

The above quote is from an RHS article, and they usually take great care to give accurate information - I find it quite amazing that a disease which has been giving so much trouble so widely, and for so long still has so many secrets about how it reproduces.
Until the information is more unambiguous I for one prefer to play it as safe as possible.

Full RHS article HERE.

[Kristen]

If I had blight I would spread the spent potting compost where Potatoes had been this year - i.e. several years, in the crop rotation, before that plot sees potatoes again.

I wouldn't mix it with composts / anything else, as it would be hard (well ... for me!!) to keep the mix segregated such that it didn't get used for something in the Tomato / Potato family next year.

You could also bag it, labelled, and use it for non Tomato / Potato uses.

Spent potting compost that is not diseased I put into a large container (or compost bags turned inside out [as in indicator]) and use it for a number of purposes.  I pot up Dahlias and Cannas and the like, lifted for the Winter.  They need fertiliser in the Spring, so the fact that the compost is spent doesn't really matter much. WHen they are planted out the compost in effect gets incorporated into the flower beds.

I used spent potting compost for Carrots in containers, as others have said, but I mix mine 50:50 with sharp sand (plus some fertiliser)

I also use it for bulking up when planting into large containers. They tend to take a lot of compost, which costs plenty, so reusing old spent compost suits me   I add some "hundreds-and-thousands" long life fertilizer and usually some manure as well as some soil based compost (easier to re-wet than pure multi-purpose compost if it ever dries out) for this job.

If I managed to have more than enough left over then it gets used as a soil conditioner when planting, for example, trees and shrubs.