Hi, I made some raised beds to grow veggies in out of untreated macrocarpa planks, because I didnt want any of those nasty chemicals leaching into the soil. However, I was wondering if there is any way of treating wood with out such nastiness. I thought I could coat them with cooking oil, it might help to repel water but I dont know if it will do much to extend the life of the macrocarpa. Do you have any ideas????? Any advise would be really appreciated, many thanks, Kim

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Some Pest amnagers now days use Borax. It was used prior to WWII and the chemical era.
Thanks Susan for your suggestion. Do you know how effective it is? I'm not even sure where I would buy it from. Cheers, Kim
hello Kim, I have macrocarpa raised beds and the supplier recommended using linseed oil on them.
Thanks Megan. I might try that
Thanks Erica. I think that is going to be the best solution
Ive just used old timber for mine and have had no problems at all, i honestly feel its a load of cobblers chemicals leaching into the soil, the amounts are probably so low as the timber would have lost most of the loose chemical, from being outside as part of an old deck, there are more things to worry about like whole sale chemical abuse especially to Home gardeners who mix up incorrect dilutions and are il educated of there greater affects!
You are probably right, but I'de rather be safe than sorry. Thanks
I have heard that no treated timber will be allowed in the production of NZ certified organic food from July this year. If they do not allow this on a commercial scale, why would you use it at home? The wood treatment used in NZ (CCA: Copper Chrome Arsenate) is banned in many countries (USA, Canada) because of safety and toxicity concerns. I would definitively advise not to use treated timber as garden edges, garden raised beds, or below any area that is using a large amount ot of treated timber (such as retainig wall). Organic NZ in a 2008 issue run 2 good articles on this matter (July/August isssue and September/October issue). The treatment is a poison that stops naturally occuring wood decay and kills micro organisms.
Thanks for your reply Diane, I agree with you. But what do you suggest as an alternative? I have spent a lot of time making all my raised beds with used untreated timber but it will rot in a few years. I wish there was a way i could slow this process safely.
HI Kim,
depending on the site conditions , height of bed, etc...untreated hardwood, such as railway sleepers should last some time. If you have a very dry site in summer, you do not want your bed to be raised too much, because humidity is in the ground. So bricks, logs, bottles turned upside down and buried slightly could be enough. Or any clean material that may become available around the garden or the nerighbourhood. Otherwise, if you are setting your bed above rubbles, concrete, poorly drained area, the following could be considered; stones, recycled concrete (old driveway being rebuilt). recycled corrugated iron, clay-concrete mixtures, or long lasting timber again .(heart wood will last longer)

Hi Kim,

Your raised beds made from Macrocarpa planks will be safe except where sap wood is used (sometimes along edge).  My husband cut down Mac's, we milled them and built our home from them.  Beautiful wood too.  More to the point we have dug up macrocarpa fence posts and they were not rotted after years of being planted!  If you scrape an old post the macrocarpa smell is still there.  The mist from milling the logs was so strong I felt a bit ill after a day of milling.  Don't know what it is but bugs do not like it for sure.



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