compost – how do you ensure you are not reintroducing weeds?

[bluebell]

I am surprised to find that I now have half a container of what looks like compost, however I can still see some roots in it so have been sieving it, but this is a bit of a slow business and I was wondering if it is any guarantee that I will not still get bits of roots in it? The reason that Im so concerned is the compost was made up of the clearing of a very weedy plot with loads of grass and bind weed.

[charles]

 If the roots are bright white, twisting and turgid, that is bindweed still alive and I would pick it out rather than put everything through a sieve.

[Pete Budd]

Hi Bluebell, I have composted literally everything in the past apart from diseased onions. I obviously would not compost japanese knotweed but thats another story. I would certainly compost; couch grass, nettles, bindweed, docks, thistles, ground elder, mares tail, etc. The thing is quite a lot of the pernicious material inc seeds and roots, dies off in the process. The composition of your compost is probably relevent, I use quite a lot of comfrey and alfalfa. Of course the more pernicious material you incorporate, the higher the risk of re-introduction but regular weed management is the answer to that, either hand weeding or shimming. Eventually you will compost less and less of the nasty stuff but don`t worry too much, just keep on top with a regular weeding strategy.

Cheers Pete

[bluebell]

Thanks Pete and Charles
I do now think I was suffering a degree of paranoia and picking out any remaining roots would be a more sensible use of my time.

[zuf]

Hello Charles.

We moved to a new farm last year, there was plenty of compost left there.
I layered it 2 inches deep on top of clean garden soil in August and broadcasted lamb’s lettuce seeds.

So many weeds germinated… especialy grass – it was in compost for sure.
Yes, we weeded like crazy, but maybe you have some other option in case like this when compost is infested with weeds and you want to broadcast small seeds in it.

It turns out this is my unaswered garden trick for now and would love some brainstorming on it – broadcasting of small seeds in clean soil or compost and keeping up with weeds in easiest way possible.

Thank you.

[charles]

 You were unlucky – mild, wet autumns are almost impossible for hoeing, and lambs lettuce grows slowly so it was a hiding to nothing I’m afraid.

Now in spring with the surface drying, sowing will be possible esp. if you have first done a hoeing in dry weather, to kill all the germinating and germinated weed seedlings, then their number is much less.

 

[bluebell]

I used the potentially weedy compost in an area where I was going to root soft fruit cuttings. This way it is fairly easy to manage any weeds that do come up (yes there have been quite a few). Otherwise sowing in modules and planting out can make weeding easier, unless it is really weedy compost.

[Dibber]

I have my compost bins next to the fence to a neighbours garden. I have put steel mesh under the tardis  type bins to allow worms in but stop mice, rats etc. The bins are in a shady position so I am not hot composting but this doesn’t matter as I have a 3 bin system working, so time isn’t of an essence. However I have had bindweed growing up through the bins. So I carefully have to sieve my compost before use. The bindweed is coming through from the neighbours garden.

Is there anything else I can do to prevent this from happening? Did think about black bagging the pernicious weeds that I had seived out. Any suggestions? Thanks.

[charles]

This is a different problem to composting roots one has weeded from the garden, and it sounds like the fleshy toots of hedge bindweed which you can pick out. Even if a few were spread with the compost, when it is on top they can easily be pulled out of the loose surface should you see any regrowth. Another factor is the length of time the compost is in your bin, maybe spread it a little sooner? so the bindweed cannot become established.

[Rhys]

I’ve overlayered both a raised bed and an asparagus row with horse manure the winter past and have had barely a weed in the past 6 months. Yes, the odd one but it’s like 2 weeds to extract every 10 days or post rainfall. It does the worms a lot of good too. To date I harvested 5lb of Asparagus (100 odd spears) in April on a 5 sqm bed, with the expectation of about another 5lb in May based on the number of spears harvested plus visible currently. So it doesn’t do it any harm although I have no previous data to compare it to to say whether yields have improved or not.

Obviously, less good for beds you want to plant lettuce into, but spuds will love it. You can also do the same in the winter once your winter onions and garlic are growing happily – I’ve done that and have been mostly weed free there all through spring.

I don’t exactly know the depth I used but 5 – 10cm over the asparagus I think and 3 – 5cm where the garlics and winter onions were.

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