Lining a raised garden bed with plastic??

brit5467(7b/8a Coastal VA)January 4, 2010

Built a raised bed from deck posts. Sides are about 6" tall. Wondering if lining sides with plastic is good idea to retain moisture since most of the plants' root system will growing in the 5" worth of compost I'm filling it with until they set root deeper down.

Also, thought it would keep dirt from 'leaking' thru side gaps between the two levels of wood posts.

Have very hot, dry summers and have to water normal garden too much already, so don't want to have to water this one even more.


Bonnie aka brit5467

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Embothrium(USDA 8 Sunset 5 WA)

Build walls so they don't have spaces for soil to spill through. Fill bed with soil so plants don't have to struggle in nothing but compost, another problem will be major settling and compost disappears.

    Bookmark   January 4, 2010 at 9:28PM
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brit5467(7b/8a Coastal VA)

The walls 'are' pretty much solid. Was just worried about the crack in between the two deck timbers.

As far as compost, I called it that, but it's actually a pretty good dense mix of compost & manure (I bought in bags) but see your point about settling. Will mix it with soil like I did in main garden....tks.

Still wondering if any harm in lining sides to retain moisture, tho....??

    Bookmark   January 5, 2010 at 9:31AM
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I don't see how it would hurt, but don't know that it's necessary. If there are data that such a lining will increase the lifespan of the wood (but, most regular thin plastic will get "holey" after awhile), that might be a reason.

A higher priority is likely the soil composition (too light or sandy and it doesn't hold moisture long), including something like the use of moisture crytals (whoa, I haven't researched those to know if make a big difference, especially re: cost) , and adequate mulching.

Is your bed "built" on bad hardpan? That will take awhile to soften up and soak water--otherwise it runs out the bottom sides. Sometimes I use a combination method, in which I'm mostly trying to do no-till raised bed due to my rocky clay soil, but maybe take my pickaxe to the soil surface and try to mix it up for a few inches (not enough for planting directly)in the hopes (?) that that will provide some additional moisture reservoir and worm action.

    Bookmark   January 5, 2010 at 10:47AM
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brit5467(7b/8a Coastal VA)

Well, that's what I was looking to find out. That so far there's no reason NOT to do it. Preserving the wood might be an advantage I'd not thought of. I've got heavy-duty industrial type black garbage bags I'd planned to cut and use, not the thin plastic.

But I'm getting the feeling from feedback that losing moisture in wooden raised beds isn't really a problem. A good mulching and good soil should be enough, huh?

Hardpan...well, I know I have clay when you dig down about 2-3 inches. I already tilled the 'good' soil prior to building it as to give me soft dirt to level the wood on top of (grade is uneven) as well as thinking eventually the roots WILL be growing down beyond bottom of bed.

Found plenty of worms (yea!!) and good to know the tilling may have helped create a 'moisture reservior' as you say.

Thanks a bunch !!
Bonnie aka brit5467

    Bookmark   January 5, 2010 at 11:39AM
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