Raised beds - what is safe?

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Raised beds - what is safe?
« on: June 19, 2020, 20:16 »
Hello! I’m an allotment newbie and would appreciate some advice please.

Our new plot is covered in weeds so we are going to try the no dig method of lining the plot with membrane and soil to kill off the weeds and then build raised beds. After much umming and ahhing in B&Q I decided on these:

https://www.diy.com/departments/blooma-pine-vertical-log-roll-300mm-1m/1906491_BQ.prd

https://www.diy.com/departments/blooma-pine-vertical-log-edging-pack-of-1/1906490_BQ.prd

I bought 4 of each with some fence posts for supporting  the inner corners to create two beds.

Now I see online that they are pressure treated. Is that a bad thing?? Would lining with membrane or rubble sacks help? I would think the chemicals in plastic would also be cause for concern for leaching chemicals? Thank you!!


« Last Edit: June 19, 2020, 20:17 by Victoria Osborne »

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Yorkie

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Re: Raised beds - what is safe?
« Reply #1 on: June 20, 2020, 01:02 »
Pressure treated should be fine in itself.

However, I would have reservations about your plan to put membrane down and then use those edges for the beds.  They are only 15cm and 30cm tall, including stakes.  That doesn't leave much growing room for plants, given the depth of roots needed - which you won't be able to get through the membrane.
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snowdrops

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Re: Raised beds - what is safe?
« Reply #2 on: June 20, 2020, 07:47 »
You say you are going to line the plot with membrane & soil in no dig fashion, I dont quite understand. With no dig you strim the weeds as close to the ground as you can, cover with a thick layer of cardboard,wet it thoroughly & cover with well rotted mulch (not soil, as it may have potential weed seeds & roots). Whatever you do enjoy, it can be confusing to start with & easy to over think it all. Membrane to cover parts you are waiting to start on is a good idea.
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Re: Raised beds - what is safe?
« Reply #3 on: June 20, 2020, 09:33 »
Hello both, thanks for replying  :)

My understanding is that raised beds are to be minimum 6 inches high and these rolls are between 5 and 7 when I measured in store.

The allotments only just opened up again after lockdown so we are being realistic about what we can manage this year. We are going to cover 2/3 of the plot and let the weeds die naturally and concentrate on the last third by clearing the weeds as much as possible and adding two beds for what we have managed to sow this year (sweetcorn, small sugar pumpkin, red cabbage, herbs, flowers, kale, spring onion). Next year we will add larger beds and probably just use these two beds for the wildflower bee friendly section.

What other timber would you recommend for raised beds? I can see tanalised raised bed kits on scaffolding direct but it is a 3 week delivery window. is tanalised ok without lining?

Many thanks!!
« Last Edit: June 20, 2020, 09:35 by Victoria Osborne »

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Yorkie

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Re: Raised beds - what is safe?
« Reply #4 on: June 20, 2020, 12:16 »
I'm not sure if we are at slight cross-purposes here.  If you're planning to use the membrane within the beds simply to line the edges, that's one thing, but if you're planning to use it as a base lining for the bed to prevent weeds coming up through it, that's a different thing.

The membrane, if used as a bottom lining, will also stop your plant roots getting down into the soil.  I think that plants such as potatoes, many carrots, parsnips, sweetcorn, tall brassicas, will all need a depth of more than 6".  So it depends on what you want to grow in there.  You'd be fine with more shallow rooted plants that are unlikely to suffer with wind rock.

Given that you've bought these now, I'd use them - I don't see a problem with them for the short term as long as you're clever about what you grow where.

Definitely use the membrane to cover up the bits you've not got to yet.  I resorted to that one year when I knew I wouldn't be able to spend much time on the plot.  Better to have a plan to stay on top of the weeds, than let them get on top of you! You're doing fine  :D

Re: Raised beds - what is safe?
« Reply #5 on: June 20, 2020, 17:29 »
Thank you for replying. I saw a method on YouTube where holes were cut into the lining of the base membrane to allow for deeper root growth. I think that will work?


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JayG

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Re: Raised beds - what is safe?
« Reply #6 on: June 20, 2020, 17:59 »
Depends what you're growing - if it's several deep rooted plants that's a lot of holes, which rather defeats the purpose of having a weed membrane in the first place.

Most of the existing weeds will be discouraged by being buried, even without a membrane.

If whatever you use to fill the beds with is weed free, you shouldn't have much weeding to do, and anything that does manage to come through will be weakened. If it isn't, you'll have weeds to deal with anyway.  ;)
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