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French Intensive and 24 inch deep raised beds?

13 years ago

Hi everyone,

I usually lurk over at the SFG boards and have posted a similar question there. But I would love to get feedback here, too, if I could. I have had only marginal success with the shallower beds and I'm getting ready to build some new garden boxes and am hoping to find some validation or discussion of deeper boxes.

I've been reading a lot about french intensive and digging to 24". From my understanding of this approach, even when you use a 6" or 12" wooden box/border, the idea is the native soil underneath the boxes has been amended and dug to 24" so that the roots can really spread out. Thats what my mom always did when I was growing up.

Well, in my case, for a variety of reasons, I really don't want to use my native soil. Not the least of which is a serious gopher problem, so I need a distinct "box" above ground that I can attach the hardware cloth to. But also, we did a lot excavation of the yard for some construction last year, so the clay soil has been compacted and has a lot of construction debris and hardpan that I don't want to deal with. And finally, long story short, there may be a smidgen of a chance of site contamination... our house was owned by am old jeweler who did a lot of work here on site and I think he may have "tossed" some of his waste into the ground out there over the decades. It's just a suspicion, but I'm reluctant to grow too close to that soil.

So here's my thought for trying more of a "french intensive" approach, but above ground. I would like to build 24" deep boxes (2 rows of 2x12's), so the boxes are deep----plus the 24" is a nice height for my back.

I KNOW the SFG people advocate shallow depth and 24" might seem like blasphemy, but I'm wondering if anyone has tried it? (I'm getting contractor's pricing on the lumber so the price difference between 2x12"s and 2x10"s and 2x8" is minimal so it would cost about the same for 20" vs 24".

For the soil, I'm bringing in a rich mixed compost from a local soil company that sells by the Cubic yard, which is a very affordable option.

I know the bottom 12" will compact over time, but I can keep the top 12" loose and compact with regular amendments of compost.

So, am I completely nuts? (OK, don't really answer that. LOL) What I really am asking is, can above ground boxes be "too big"? Are there any potential pitfalls of a deep box? I realize some people will say it's wasteful and unneccessary, but aside from that fact, will it work?



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