Topic: Bark chippings on a vegetable bed

[busy_lizzie]

Hi, I am secretary of a community allotment, and I have also had my own allotment on a larger site for over ten years. I have recently been able to get some bark chippings for our paths. However, when I was there today I saw one of our plot holders spreading the bark chippings around their veggie plants,  (he had lettuces and courgettes amongst other things in). I mentioned I was a bit concerned for his plants, and did he think it was the right thing to do? I know I should have minded my own business, but my intentions were to help.  He became quite cross and said he had been doing it for years in his garden at home, and it was fine, and he would do what he wanted on his own plot.

Has anyone heard of bark chippings being spread over vegetables and being a succssful mulch. He was using it as a weed suppressent. I would be really interested to hear anyones views. Thanks, busy_lizzie   

[goodlife]

Umm...hmm....it all depends of the chippings. The better quality ones that are proper bark, not wood chip, are 'treated' so that the harmful but natural chemical that wouldn't affect plant growth. If I remember right..bark has been heat or steam treated (or something along the line).
Normal woodchip I would not put straight on amongst the plants..and even I would..it would all depend of the type of wood. Chippings from conifers and such a thing (with resin) is definite no no..but something like birch propably would be fine with helping of high nitrogen feed scattered amongst it.

[busy_lizzie]

Hi goodlife, Thanks for your comments. The bark chippings were just obtained from the council free of charge, so I presume they will be from a variety of trees. The plotholder can do whatever he wants on his own plot, and it isnt any of my business really, but to me it just seemed wrong to put raw chippings around your veggies. I could hardly see the vegetables when he had done with it.  I am going to be viewing his plot with interest. Everything is a learning experience, and nobody knows it all, so it will be fascinating to see the outcome.  busy_lizzie 

[manicscousers]

We have spread rotted bark around our strawberries instead of straw. Never had such a good year. Also spread it around the courgettes bed but they are in tyres, 8" above the bark. They're going great guns 

[cambourne7]

I was always under the impression it affects the PH level maybe its for the good with some plants?

As for there bad temper might be the heat :)

[ARV]

I'm using a layer of cardboard covered with bark chippings as a mulch/weed suppressant around my fruit trees and bushes including under some strawberries and around the larger established herbs (bay, rosemary, sage etc.). That works very well. 
I'd have thought that using them on a veg bed would be ok for larger plants like the Courgettes and Squashes and around the base of brassicas. I don't think it would work too well around carrots, parsnips etc.
My concern would be the next year when you rotated the vegetables that you're growing.  Trying to get a fine tithe for sowing small seeds would be hindered as the chips would still be fairly large. 
I also understood that the addition of wood or bark chips would cause a nitrogen deficit in the soil initially, but as the chips rotted down the nitrogen would be released again (but over the 2-4 yr period it would take the wood chips to rot).

[Robert_Brenchley]

I did it once with overwintered broad beans. There wasn't a problem, but of course legumes have their own nitrate supply so wouldn't be affected by any shortage. Rotting chippings will take some nitrogen from the soil, but I'm not sure how much or whether it would affect vegetable growth.

[Ian Pearson]

Bark chippings? or chipped prunings? It makes difference. Chippings from tree prunings as provided by tree surgeons are what is usually available, and contain more nitrogen that you might suppose at this time of year (being in leaf). Hence the high temperature that it will achieve after a couple of days in a heap. Laid on the surface of the soil, I've not noticed any signs of nitrogen robbery, and I regularly use it to mulch round perennials, and larger veg such as climbing beans, peas, courgettes, squash, corn, tomatoes ... but not on root crops, because you don't want it getting mixed in with the soil at harvest time. It can be left on the soil surface along with crop debris to protect the soil, and by spring, there is not much left of it.
Personally, I prefer to let it compost for a week or so before application though.

[busy_lizzie]

Thanks for all your comments. I really appreciate your input. busy_lizzie

[Vinlander]

As Ian Pearson said above - there is a big difference between bark and prunings and woodchip.

Bark contains lots of tannins - it's almost like peat, and rots slowly enough to have no effect on the nitrogen content of your soil.
Prunings vary depending on how green they are - if they are very green they are exactly like spent bean haulms etc. and make an excellent mulch - they have a good C:N ratio and when they get wet (eg.in the soil) will rot quickly with no problems of nitrogen theft (or the excess heat you can get from grass clippings).

Woody prunings are effectively woodchip and it all depends on the size of the chips.

If there is fibre or sawdust or mm size chips in there it will rob nitrogen for a year or so - and it needs to be stored for 1,2 or even 3 years before this process has finished. I do this in my deep trench paths between raised beds - after 3 years it is an incredibly good soil improver on heavy clay.

If you have a garden vacuum then conceivably you could put 2-5cm of fresh woodchip over some kind of plastic (which would protect the plastic/fabric) and hoover it off later before you dig the crops.

The remaining big chunks (10mm plus) have too much surface area to rot quickly and will therefore behave very like small stones for the 10 years they will take to rot. It is all about the square/cube law - big things have comparatively much less surface area to react through.

If what's supplied are ALL big chunks (usually only if you chop them yourself by hand) then they are probably OK to use anywhere - though there will be a risk of spreading fungal diseases in such big chunks (the RHS says the smaller size of the chips is what makes woodchip unlikely to pass on eg. honey fungus).

Life is complicated if you want to maximise your gain from every resource - you can spend so much time finessing how green you are that you don't have time to do anything! (maybe I should add that as a maxim below).

Cheers.

[GrannieAnnie]

If there is black walnut chipped up it could kill off plants due to a chemical juglone within the tree, mainly in the roots, but some also in the rest of the tree . Also Hemlock has a similar capability of stunting/killing plants.

[Vinlander]

Black walnut is pretty rare outside an arboretum, and hemlock would be even rarer in a normal garden wouldn't it?

I did forget eucalyptus which is widespread and known to contain a growth suppressor - mainly in the fallen leaves to stunt the competition but probably in other bits. Good for paths though - but maybe give it an extra year to rot.

A lot depends on what you grow - tomatoes are thugs - when I did an experiment with coffee grounds - chop suey greens hated them to death (their own) - but tomatoes didn't even notice at twice the concentration.

Cheers.

[GrannieAnnie]

They aren't rare in our area of the U.S.A., in fact we have 6 hemlocks bordering our yard, but perhaps they are in your area. Other trees that have a lesser amt. of the detrimental chemicals (googled straight off the internet): English walnut, butternut, pecan, shagbark hickory, tree-of-heaven (Ailanthus altissima), sugar maple (Acer saccharum), hackberry (Celtis spp.), and American elm (Ulmus americana).

[Vinlander]

It just shows me how a little knowledge can completely derail my understanding - especially across the pond...

I'm pretty ignorant of any plant you can't eat - with the exception of a few that have a really nice scent - and most of those I really like (eg. philadelphus) smell like food (raspberries and cream in the case of the one in my front garden).

So despite a few hints that we weren't talking about umbellifers (even big ones), the combination of poisons and hemlock took me straight to Socrates' bane!

To me the Tsugas are just another pine - and all the worse for casting shade all year round - just another bloody ornamental blocking light from my own plants which are both beautiful and useful in the best tradition of William Morris and the edible ornamental movement which is unfortunately not as well established over here.

However it is surprising how many good food producing trees are in your list.

Cheers.

PS. If hemlock (Tsuga) tea is widely used in the US then surely there must be the occasional fatal misunderstanding?