Sawdust as a temporary weed-suppressing mulch

Have a load of sawdust at the allotment and want to use it there as a mulch to suppress/kill weeds. I know it robs the soil of nitrogen, but isn't there a way to er, re-nitrogenise it? The soil is also heavy clay so I thought digging it in when I eventually planted might make it lighter.

Thanks,

Nick

 

You can use it over autumn and winter Nick....I have done it. You will have to feed the plants there though in spring; you are right, it does use up nitrogen in the soil whilst breaking down. Frankly though I think it’s a negligible loss only

 

Thanks @Verdun, I'll probably eventually plant strawberries and raspberries there, do you think they'll need much feeding after I mulch in Autumn, and what should I feed them with?

Nick

 

Organic Nick....fish blood and bone, chicken pellets etc . Mulch strawberries with straw when fruit is forming. Raspberries with
Remember, organic feeds take longer to work so I apply fb and b a few weeks before growth starts in spring.

 

If the sawdust is from pine, or other coniferous woods, do not on any account use it as a mulch. It needs to be composted for an absolute minimum of 6 months to get rid of the toxins it contains. A good trick after that is to mix it properly, 50/50 with grass cuttings. Although not perfect, it vastly improves it for use in gardens, allotments etc.

In regards to strawberries. We dont need to mulch them here, in our climate, so really, it shouldnt be needed in the UK either. In fact, I/others here dont even fertilise them either.

 

I mulch the strawberries for one reason only......it deters slugs and snails.

 

@Sandy Ground Thanks very much for the useful advice re sawdust. Oh dear, not sure what sort of trees it's actually from! Perhaps best to compost it anyway, then. Could I just leave it in the very large bags it's in for 6 months, would that have the same effect?

Heavy clay and not very well worked by the previous owner here, so I think perhaps best to mulch with straw anyway. Tried it on a patch my friend gave me for a while (to see how I would cope before getting a larger plot). Only three inches of the stuff and worked well in terms of suppressing weeds.

Nick

 

Completely forgot that it was useful in that way too, thanks for mentioning!

Nick

 

I can only speak from my own experience....sawdust works well on its own....not to be used in the growing season though

Yep, straw is very effective for that Nick.....not a single fruit damaged by slug or snail and a prolific crop that only tailed off a couple of weeks back.

Re grass clippings....I once made the mistake of adding grass clippings to my veg patch as a mulch. It created lots of weed grass there. For me grass clippings are best used in the compost heap.

For me, as always, I take advice from everyone, listen, experiment and then make up my mind as to what works for me.

 

I tried it for a while but found out that rather than making clay more workable it actually held moisture and made it more claggy.

I can get loads of it, but never use it, personally I found it to be more trouble than its worth.

If you can add it slowly to a compost heap I think it might work, but on its own just dug in I don't like it.

 

Thanks for that @pete, very interesting comment! I've read somewhere that its particles can sometimes adhere on the surface and form a sort of 'sheet' if used as a mulch and create problems in that way. So what you're saying seems to make sense. Perhaps straw would be a much better option.

Nick

 

Straw is better if you can get it IMO, it breaks down faster and is less claggy.

Many years ago I tried it as a winter mulch on plants that were not totally hardy, always seemed to get very wet and cause rotting.

 

Hmm... lots of conflicting and confusing info on the internet (isn't it always the case?) but it sounds like it would be better used in small quantities rather than large ones. The weed-killing effect seems legit and might be best just used on the surface in problem areas. Acid-loving plants are aided by it but it sounds like more of a thorough sprinkling rather than a thick mulch might be beneficial, which would stop a crust forming. Digging in doesn't sound like a good idea considering nitrogen loss at root level. The phytotoxic effect which Sandy Ground mentioned regarding conifer sawdust seems to be more relevant to younger plants, so perhaps best to just use it on mature ones such as my blueberry bushes. Some experimenting required here I think.

Woody waste: using as a mulch / RHS Gardening

Nick

 

Sorry, didn't quite explain myself properly. I meant digging in as a benefit, will try it a bit as a weed-killer to see what effect it produces.

Nick

 

OK, maybe I got the wrong end of the stick

Shreddings are different to sawdust.