Fill Bottom Of Deep Raised Garden Bed With Organic Materials

I’m building three additional fairly deep raised garden beds. You might consider covering the bottom with organic materials. That is, before you add the soil. Why? For the organic goodness, and, save some money on garden soil (assuming you’re buying it).

I took some pictures of what I just did for the purpose of this post. Maybe it will help someone out there with this idea.

I live in northern New Hampshire. We have rocky, sandy soil (generally speaking). We’re called the granite state for a reason… There are pockets of pretty good top soil, while there are also areas that are not so ideal for using in a raised garden bed. Consequently for some, it’s best to buy garden soil for a new raised garden bed. Then, each year, amend that soil with compost to keep it nutrient rich.

Okay, back to the new raised garden beds… I built them with 2x8x8′ lumber, stacked two boards tall. So, that’s 14.5 inches tall. Therefore, it helps a little on the back – bending over compared with just one board tall. But here’s the thing… How much dirt do you need to fill a raised garden bed of that dimension and height? Well, it’s simple math:

Square feet x height = volume

Each of my raised garden beds would require 32 cubic feet of soil, if I filled it a foot deep (8′ x 4′ x 1′). A little bit more for mine, given that it’s a bit taller. The amount you will actually need may vary somewhat depending on the soil you buy, because there is (in my experience) variability as to how a manufacturer quantifies their soil. How compressed is it when they claim 1 cubic foot per bag? Or 1.5 cubic feet per bag? Anyway, that’s not the point I’m trying to make. Rather, I’m giving you a tip how to save some money on garden soil in raised garden beds, and, the goodness that this will bring to your garden…

Here’s what I did:

rotting branches and logs in bottom of raised garden bed

I have a lot of trees on the property here at the homestead. A combination of softwoods (spruce, fir, etc.), birch, and maple. The tree ecosystem is always in cycle — birth, growth, maturity, end-of-life, and weather events blowing them over. As a result, when trees finally fall, they will eventually rot in the ground. Because of this, I don’t have to wander far on the property to come across rich organic rotting wood in various stages of decay.

I gathered enough of it to place at the bottom of my new raised garden beds.

Organic Rotting Materials Creates A Rich Ecosystem For Raised Garden Beds

You can put in just about any organic materials at the bottom. This might include leaves, branches, rotting logs and limbs, compost, etc..

These materials will invite worms, bugs, and microscopic organisms all good for your garden. Over time, these will continue to decompose, further feeding the system. Plus, as a side bonus, you’ve saved some money on garden soil.

Time to fill the raised garden beds. Made the trip to Home Depot and picked up a pallet of Vigaro general purpose garden soil. Drive home, back up the truck to the raised garden bed, lay a bag on the tailgate, slice the end open, let gravity do the rest…

Have any of you done something similar to this? What organic materials did you use?

40 Comments

  1. Real similar to Hugelkulture mr J.
    Good idea too.
    One thing, wont those boxes rot out pretty fast? I know if i did that here and didnt put plastic or something like that between the wood and soil it would all be rotten and falling apart in less than 2 years.

    1. Even though it’s PT lumber, it will still eventually rot. An endless battle I suppose. I’ve been at this property for 8 years. Built the first bed here ~ 7 years ago and it’s definitely getting soft now… I realize that they’re time limited. I’ve read that lining with plastic will increase the speed of rot (moisture traps between the plastic and the lumber). When it comes time to rebuild my oldest raised bed, I’m sure I’ll make an article about it ;)

      1. There is a product they sell that goes up against your foundation before backfilling and after water proofing, looks like black hard plastic bubble wrap, maybe that would work? Im sure up there in the states its available, around here not so much because not many basements or concrete wall foundations. I really want to build some raised beds and re do my garden, just too hard to control it all, figure the designated beds may be the ticket, filling the bottom with branches etc is an excellent idea to gain elevation. Thanks for the idea!

      2. Perhaps consider corrugated metal instead of wood. You might look at Birdie’s raised beds or Vego garden beds. I’ve had a good luck with both. 20 year life.

      3. We did this about 10 years ago and our beds needed to be replaced last year and next year. We replaced them with lick tubs but are not that thrilled with them. Seems like the plants like to spread there feet out horizontal. We have a 8×4 foot to replace next year and we are going to try galvanized roofing on the cap concrete blocks he laid over the whole garden. The others were raised so I didn’t have to bend over and now that I am older, it looks like I will again! We have 2 more 8 foot beds, one is fine and the other we lined with plastic- the only one. It was also the first one we put in and it is fine, no problems. It does hold water and when we get rain (what is rain?) it can flood the bed. The wood didn’t actually rot very much, mostly it buckled. 10 years ago Old man asked the man at the hardware store if he would have a problem with the wood rotting and the man said not in your life time. Guess he fooled him!

      4. I made raised beds using western red cedar lumber. It was pricey 8 years ago but out of sight today.

        The beds were 18 inches deep. 2′ x 6′. Screwed together. I used 1/2″ galvanized fabric wire with intermediate supports. Covered the wire with garden fabric to keep the soil in. Filled with compost. Grew incredible amounts of tomato, pepper, okra.

        After 6 years the screws failed (sheared from rust damage). I repurposed the cedar for a firewood bin.

        This year I’m using cinder block beds. One is two blocks high and another is three blocks high. We live on a mountain top with virtually no soils.

        Following your discussion Ken, I’m using hardwood mulch on the bottom of the beds. This will help keep the soils from washing down through the rocky planting area. I add some earthworms to my garden soil. Ill use 100% compost again. Supplement with Nitron organic fertilizer.

        After all that. I’ll have to fence the beds off from deer and ground hogs. Hope to plant sweet potatoes and acorn squash in the small bed.

  2. @Ken – great article! I have been pondering what to put in the bottom of raised beds and like you have a bunch of fallen trees.

    1. No, they’re not. I cut them to 14″ lengths and used them as corner supports (it’s what the 2×8’s are screwed into). The bed simply sets on the surface of the ground.

  3. I did much the same with dead dry grass and the attached root ball within the 1/2 wine barrels I use for raised beds within my yard. It makes sense to keep the nutrients and good micro-organisms in the soil. I live on an old pasture so most of the biomass from my yard is grass clippings or root balls. The grass clippings get removed every week. This method inspired by hugelkulture minimizes the amount of additional soil and amendments I add to the soil each year. Last year and this year, I anticipate adding 1 maybe 2 bags of potting soil to the 5 wine barrels in my backyard. I mix in a balanced fertilizer at the start of planting and just let things grow.

    The most durable looking garden beds appear to belong to hermit us in Idaho. Does he dig down deep each year and turn over his soil within those concrete beds? Each area presents is own challenges. In the desert region I used to live in, I partially buried the containers in the clay soil and put up shade cloth to moderate the temperature of the potting soil within the containers that grew plants and vegetables. Container gardening was essential in the desert in order to hold the soil in place from the constant, dry winds that are present in my zone.

  4. I just started filling my new beds I’ve added to the garden like this also. But, I’ve used much smaller yard waste. Smaller branches and such. Then I top with a mixture of garden soil, a bit of manure (store-bought or well-aged chicken), and some vermiculite. Mix well. Even a bit of sand if I’m growing more root crops and want better drainage. I’ve also filled a few beds with composted shavings from the chicken coop, filling the bed about a third. Just swiped them from the compost pile. I’ve also been watching Youtube videos by “Edibleacres” and this guy is amazing how he works his chickens and his (very quick) compost system. His food forest gardening and natural planting methods are really amazing. I think he has a website by the same name tho I haven’t checked it out yet.

    Does anyone add kitchen waste directly to their beds? We get raccoons and/or ‘possums if we do, and I don’t want them here because of the chickens. I use a sealed compost tumbler off its stand and just roll that around in the yard for kitchen waste. Works for me. I’m just curious if anyone does it directly in the garden.

    1. DJ5280,
      i wouldn’t do it because of attracting critters that would eat up everything else while they are there. just my 2cts
      compost it first.

    2. DJ5280, My parents ran all their kitchen snd yard waste through their chickens. I run mine through my pigs. Quick, concentrated, and rich.

    3. Kitchen Waste in Garden
      I have in the past just buried (no meat) it about a foot deep in different spots in the garden I also put water on it to help it along (although I live in a rainy part of Washington St), looked at one of the spots later could not find any sign of what was buried?
      No animals dug it up?
      So worked for me

    4. I add all of my kitchen scraps directly to my gardens, for 10 years. No problem with bears, moose, or hares. They have lots to eat in the woods.

  5. Ken,
    as we get older, gravity is our friend, and sometimes foe.
    i try and use it to my advantage : )
    good luck with the garden!

  6. i commend everyone for starting their gardens. i have started some containers this year as an experiment, it will be easier if it works but i have not put all of my ducks in one row. we have 2 acres planted in row crops, enough for two years worth if it makes. ya never know, it may make and it may not. we still have 2 yrs of canned food put back i think, it’s everywhere. and we are quickly running out of room to store it all. we can grow it faster than we can eat it. we weren’t going to plant a garden this year but we were afraid not to.
    DW and i have talked about giving the garden a rest, and us, next year and to rotate down what we have put up. we’ll see.
    good luck with everything guys.

  7. We put in a layer of punky birch, for all the reasons mentioned, plus for moisture “storage.”
    Trying to come up with a home for strawberry plants, we made raised beds — single 2×6 wide and three 2×6’s deep. These beds have a 2×6 floor and are elevated on legs.
    For us, anything we can do to warm the soil is paramount. The narrow bed would warm thru nicely but likely to dry out quickly.
    We first soak the birch, in water, to get a head start.
    Also add partially composted grass aka core gardening.
    Then sprinkle bloodmeal over this before adding the garden soil.
    As I’ve mentioned, birch has some really off the wall characteristics. Back in the day pot growers used the soil from a birch tree’s root ball. Likewise, if you are guerilla gardening it is a good idea to plant around the base of birch trees. So, whatever it is that the birch logs are adding…?
    Just to throw it out there, if you smoke (foods) try using punky birch instead of hickory et all. It gives a really nice, unique flavor.
    It’s all a learning process.

  8. I read yesterday that Australia is looking at nationwide legislation prohibiting citizens from growing their own food. It is expected to become law.

    1. Australia began as penal colony that has turned themselves into a slave colony. Anyone that bows their head to those “royal” POS deserve everything they get.

  9. We feed the cows round bales of hay during the winter. In the spring I take my tractor and pile up all of the manure and old rotted hay that is left and let it sit for about a year. This turns into a rich black dirt. I put it in my garden, in flower beds and in my raised tomato beds. This stuff is wonderful, and it’s cheap and plentiful here at my house. Also put old coffee grounds and egg shells in the raised beds. A lot of our “waste” has a purpose if you use your imagination. And we save dryer lint for fire starter in the wood stove.

    1. I laughed when I read today’s blog about raised garden beds. I happened to be waiting for DH to get home from work so we could work on our new raised garden beds while there was a break in the rain. It’s been rough getting the garden ready this year because of too much rain, hail, and cold. Not sure we can safely plant even now, but it won’t matter if we can’t get the garden beds finished.

      I thought I’d add my two cents worth on the subject. We used pressure treated wood on our four 4’x8′ beds, and we’re following lasagna gardening suggestions I gleaned from different sites. We placed landscape fabric on the bottom and stapled it to the sides of the wood. Then we placed a layer of cardboard, then a layer of decaying wood and branches. Next we added grass clippings and then bagged soil. I wanted to add some manure too, but it’s too wet to easily move it from where it’s at right now. If I can’t use it this round, I’ll add some in the fall. I do add vermiculite too, but usually around the plants or seeds when I’m planting.

      We have an old leaky horse trough I’m repurposing to raise potatoes in and I placed the same layers in it, starting with the decaying wood.

      I’m curious about what caused some of your garden boxes to rot at less than ten years. We have older, smaller ones made of whatever pressure treated wood was available at the time. They’re still solid. One is bowed due to a tree trunk beside it, but they have to be at least 15 years old. Maybe our milder Maritime temperatures have something to do with it. Anyway, happy raised garden bed gardening! We’ll have to compare notes throughout the season.

  10. I use my middle buster and break out a deep furrow. I then fill it with leaves in the spring and fall or if its time bedding from the chicken house. A new row each year builds the garden over time. I put kitchen waste in my banana beds. They really like a high organic matter content soil.

  11. God’s nature provides so much of what we need. I mulch my Blueberries with pine needles, our Blackberries get a yearly mulch of Oak leaves, much of our compost pile is hay, animal waste, leaves, pine bark and needles. When adding to our raised beds, I start with putting down a layer of cardboard, then organic matter, followed by composted dirt. To keep the grass down around the beds I place a thick layer of oak leaves as mulch also.

  12. I had to laugh at the timing of your article Ken. This is exactly what we have been working on for a new strawberry bed! I put a bit more wood in the bottom though. Then chipped wood that sat awhile for the 4x 12 ft strawberry bed. We can collect old leaves from the outer perimeter woods and it is inoculated with pig poop. Then our top soil. We have a good supply of mulch sitting from last year. This is a modified version of our hugels that we have been building. The bottom has black landscape fabric that lets water through. My beds that will surround the outer perimeter of the garden will have hardware clothe to keep out the voles, moles, etc. and these are two boards (20 inches) high. We can place old window frames on top for longer growing season.

    Our larger hugels have larger logs on bottom base, then another layer of logs next level up, then branches, then old, used straw from chicken and goat pens and so on. These hugels don’t have wood sides and they grow amazingly well. The logs hold and release water as needed. They will slowly deteriorate but you just add new “compost” to the top each year. It helps you get through droughts and protects the plants during heavy rain periods. You can plant on tops and sides of the hugel and inter planting is encouraged as it helps the plants themselves.

    1. Ive been wondering if its ok to use coniferous branches etc in my hugels? Or even in beds like these ones KJ wrote about. Have a ton of branches from trees we lost in a storm late last year, Monterey cypress, dont have the energy or time to run all that stuff through the chipper and this article brought me back to the subject. I guess i need to do some reading.

  13. Use concrete cinder blocks, cheap and will not rot. Do you think “pressure treated wood” has the type of chemicals you really want leaching out in your garden???

  14. Leaves… I filled the bottom of my raised bed with Leaves, mainly maple leaves. That years crop in those beds were amazing. My raised beds are built with concrete garden wall stones stacked 4 high. Years ago I started with wood frames, but they deteriorated.

    1. Mr. Floben,

      I’m trying that myself this year. I filled my containers (5 gal buckets and 20 gal tubs) 1/2 full of last years leaves, mashed down to about 8″, covered with about 3-4″ of chicken poop/litter, then filling with potting soil. We’ll see how it works out for me. Thanks for affirming my own experiment.

      1. Dennis,
        doing the same thing here with the 5 gal buckets as an experiment, we’ll see. we still have our row crops as backups.

    2. Mr. Floben,
      if i was to ever build some permanent raised beds i would use cinder blocks. you know, buy once and cry once.
      like the man said “get er done”. having to rebuild things after just a few years is not a sustainable or economically sound practice. but that,s just me.
      good luck with everything!
      my garden is coming up good, we need some rain though, its forecasted for this weekend. hope we get some.

  15. Ken, I found a product at gardeners dot com called “Lifetime Raised Bed Corners” that makes it very quick and easy to build the framework. They are pricey but the older I get the more I’ll pay for easy. If you have time take a look and see what you think.

  16. About 5 years ago i put in 5 raised beds and ran out of dirt for the last one . I filled the bed with corn stocks and covered with dirt. Planted tomatoes. it was a very dry year and the corn bed stocks produced best.

  17. I’ve done that sort of thing for ages– I couldn’t afford to fill raised beds with bought soil. I don’t use pressure treated wood, but use round cedar cut for fence posts. I’ve also tried a few mounds of stuff instead of the work of building a raised bed. Its not pretty but it works and is cheap.

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