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can someone advise my compost / peat in greenhouse as turned green on top and in my raised boxes is now feeling sandy how often do i need to change it.

or can i feed it to get more life from it.

or do i cut my losses and replace it all if so with what.

i try so hard but my results are never good.

i will admit i do feed plant ie toms cucumber and veg nearly everyday and my wife reckons i overfeed.

please somebody advise i know its longwinded i just need to get it right thank you.

If the compost has been there since last year, I'd definately change it, probably completely. Unless you intend to use it for some winter lettuce I'd change it a week or two before you need to put in any new crops.

The stuff growing on the top isn't a problem and is growing as its warmer in the greenhouse than outside.

I'd use it as a dressing on the beds outside.

I would use fresh compost every year.

Dollo, I would use it too as a mulch outside

thanks dave and verdun for replying will probably change 50% can you recommend a good compost for inside greenhouse or is it best to just using grow bags.


There are now some good peat free composts around, I've been peat free for several years now - a shaky start but now it seems to be OK.  I use old compost in the bottom of pots, as a mulch anywhere, and in the bottom of baskets, with new good stuff on top - works for me.

Personally I don't like grow bags, the root space is too shallow, since I started using deep pots for tomatoes etc. in the greenhouse, it goes better.

The green algae on the compost is harmless, but does indicate wetness.

Feeding daily is too much, better to use a good quality feed weekly, or a pelleted one now and again.  Over fed plants just get long, pale and weak, as it is said  'treat 'em mean and grow 'em hard'  for good results. Let the plants do the work, you are just the carer!


dollo, I'd use peat free too, depending on what you are growing later, I do add some garden compost from the heap, and a bit of well rotted manure.

Some don't do this, but I find it gives a very fertile bed, and it should if done now, rot down very quickly, just dont use too much ( a few handfuls per 2 sq ft) otherwise you get greenery and no fruit.

I do it the way my grandfather did it, others use the commercial fertilizers.

Change the compost every year !?!?  That's a bit of a blow. I had a big birthday last year and got a poly tunnel from my hubby. I've just put in a vine and plan to do sweet potatoes. The cost will be huge as it's quite a big area. 

I may think about putting down some grit and keeping the soil area to a minimum, and think about using more large pots.

learning a lot from this forum.


 With a big area, obviously the cost and effort to replace all soil would be enormous. Why not add a layer of new compost on top to give a bit of "ooomph" to get things going once they're planted. Once the roots get down deeper, into the older compost, you'll probably be liquid feeding anyway. My polytunnel is 56feet by 23 feet and I'd be bankrupt if I had to replace compost every year. Good luck.

That's a relief. We bought some decent soil from Rolawn. Think it was more topsoil with added ????

forgot already.

So the reason for changing the soil is to keep the goodness there, to produce good plants. I was afraid the reason was bacteria or disease and thats why you had to change the soil. 

Trying to keep up. Thanks.

No expert

I believe when they say change the compost every year they mean in your pots.


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