Raising the beds - any ideas on a simple/economical retaining wall for the base?

First of all, in the photo you'll see my Labor Day Labor of Love: Prepping the garden with raised bases on which my three square foot garden boxes (4'x8' & 8' high) will go. I still have more prepping before I lay the weed mat and river rock. Having them raised has a couple of benefits. The primary reason is that this is the northeast side of the house which gets a lot of shade in the Winter. Raising them gives the plants a little more direct sun. 

BTW, notice the sand is like white beach sand? Here in S. Florida, I can dig down 1.5' anywhere on our property and find this stuff. So I dug a bunch of holes to get this and then buried the layers of root knot nematode contaminated soil. It was a lot of extra work but I feel better about having a layer of nematode free sand to separate the plywood box bottom contaminated soil. Plus they'd have to get through the weed mat and a layer of river rock.


Here's where I'm opening this up to advice your advice... Once the boxes are built I'll add little concrete retaining walls to hold the sand in place. I'm trying to not spend a lot of money on these bases as raising the beds like this was an afterthought. I'm thinking I'd wrap the bases in something like chicken wire and slap some Quikcrete on and smooth it out, just to hold the sand base together. Does this sound okay? Any other economical ideas? 

Well, I can't believe I lost everything I wrote when I went to retrieve this link. Need another cup of coffee.   Look at how Brainchasm built his beds.

https://squarefoot.forumotion.com/t14727-newbie-in-las-vegas-year-1?highlight=Las+Vegas

I voted for Other.  Sloped slides can make it really difficult to get close to the beds.  Either your feet will be stressed standing Uphill or it will be awkward if you try to kneel.  Flat ground approaching the boxes and vertical sides of the boxes is optimum.

My idea is to use cinder blocks for your base around the hilled dirt. Drive rebar into the ground inside the holes to keep the blocks from migrating outwards.  Or stagger the blocks and fill with concrete.   Level the sand/dirt inside.  Lay the plywood (don't forget to drill 1" holes at each corner plus one in the middle of each of the square feet) and weed screen over the now-leveled dirt.  Then build the beds of cinder blocks directly on top of the base cinder blocks.  Wella!

Cinder blocks will last for years.

One thing you may want to consider if using cinder blocks is using plastic between the blocks and the soil.  I think the cinder blocks really like to wick a lot of water out of the Mel's Mix.  It seemed to have done so in my cinder block setup.

I vote for sanderson's idea of cinder blocks. If you don't like the look, you can parge and paint the outer face.

My neighbor who uses cinderblocks has by far the best and most abundant veggies around. I like my cherry tomatoes, but his are otherwordly-good. We both grow Sweet 100 and Sungolds, and ours taste nothing like each other. Another hearty vote for them from me too.

Incidentally, he tells me some things about them that recommend them to me very highly -- he says they store heat accumulated during the day and let it off slowly at night, keeping the temperature variations from being so drastic like we get here -- 30 degree difference or more between night and day. You can have it both too cold and too hot for tomatoes blossoms to set fruit on the same day for weeks in a row. Vice-versa, they also moderate the 100+ temps we can get on summer days by retaining some of the night's cool. That general temperature modulation also helps him grow his tomatoes a bit later into the season.

For me, there's also the appeal of sticking a few lettuces or flowers in the holes or such-like. He doesn't do it, but I would, and you might.

I get the cinder blocks for elevation, but what keeps the wooden bottoms of the raised boxes from rotting out, since I assume you're not using pressured treated lumber on a box used for growing food.

Does having raised beds mean rebuilding the boxes every two or three years? My back started hurting a bit getting down to ground level, so at age 55 I am thinking about starting to raise my boxes next year. Will it hurt anything if I start building them over the winter and cover the empty boxes with tarps?

Maria

I really like what Brainchasm has done with cinder blocks.  A quick cost estimate shows his box is higher and 1/3 the cost of my redwood box, although his does not have a bottom.

 A cheap, replaceable bottom could be made from a single sheet of 4' x 8' x 5/8" exterior grade P/W, framed with 2 x 2 white wood edges, and 2 x 2 WW sleepers every foot.  About an hours work, and  $50  For another $25, get cedar plywood and redwood sleepers.

Hope this helps...

aerodyne

Aerodyne,  Ditto on Brainchasm's cinder blocks.

Regarding the plywood bottom, I'm not sure if you are referring to Table Top style boxes that are totally above ground or like D Stack is doing with a filler sand material base with MM boxes on top.

For true TT boxes, the plywood bottom would eventually have to be replaced.  Ugh, I would hate to have to take everything apart. I think Mel recommends 5/8" or 3/4" bottom for 4' x 4' boxes.

In Stack's case, the plywood will be resting on the filler material. Eventually the plywood will de-laminate and even rot. But I wouldn't think the plywood would need to be replaced.  I think most of the wood fibers or duff will just sit there, still doing what it was intended.

What are sleepers?  A type of decorative vertical trim or support? Not familiar with that term. Some folks have really made some pretty boxes.

WriterCPA wrote:I get the cinder blocks for elevation, but what keeps the wooden bottoms of the raised boxes from rotting out, since I assume you're not using pressured treated lumber on a box used for growing food.

Does having raised beds mean rebuilding the boxes every two or three years?  My back started hurting a bit getting down to ground level, so at age 55 I am thinking about starting to raise my boxes next year.  Will it hurt anything if I start building them over the winter and cover the empty boxes with tarps?

Maria

Maria,  D Stack is planning to set the plywood on top of his filler material.  I stated in my reply to Aerodyne, the wood will rot but the remains shouldn't go anywhere in his design.

I think higher boxes would be nice, more comfortable on the back or more compatible with a stool.  I told husband (as we have been discussing D Stack's raised beds) that someday my knees won't take the kneeling I do at this time.  My first boxes this spring were made of 2" x 4", 2 layers = 7" tall boxes.  We are adding a third layer to make them more attractive.  The new boxes built last month are 3 layers of 2" x " 4", = 10 1/2" high.  If I need them higher, I would remove the expensive MM, saving on a tarp, place ordinary soil in the bottom, level it, add weed screen over the soil, and replace the MM at the top, leaving enough room for an inch of wood chips as mulch.  My current wood boxes are open bottom to the soil with just a layer of weed screen at the bottom of the boxes, extending up the inside walls 2".

If I had an area for larger boxes, such as 3 x 6', and wanted raised beds, I would consider cinder blocks with artificial turf in the isles.  I would have a solid base of cinder block, fill the block spaces with sand, water to settle, then lay 2 layers of weed screen over the filled block, make the top of the box of 2 x 4's, and fill with MM.  I wouldn't use a plywood bottom under the MM.

I have to use bottoms because on invasive gophers and tree roots.  Myy climate is dry, so if the wood bottom is supported of the ground with a sleeper (A stick of scrap lumber used in lumber yards to keep stacks of wood dry)  The plywood will take years to degrade.  If one is going to raise the bed to table height, I would stick with wood and use a cedar plywood bottom.

aerodyne

How high does one one raise the beds for climbing plants?

I was thinking about raising my root and lower plant boxes to three feet from the ground, but at 5' tall, I already have enough trouble with things growing to 6'+ on my verticals when the roots are ground level. I can just see myself using a reaching stick or chase cukes, tomatoes, and melons at the top of the netting. 

Have you thought of harvesting them using a trampoline?

I'll call my neighbor's son right over with his. They have huge net side walls on the thing to contain him. It worked OK in April, but I think he grew three inches and added booster packs to his sneakers over the summer. I just seen lots of blonde hair flying like an animated sunflower on the other side of my garage! 

WriterCPA wrote:How high does one one raise the beds for climbing plants?

I was thinking about raising my root and lower plant boxes to three feet from the ground, but at 5' tall, I already have enough trouble with things growing to 6'+ on my verticals when the roots are ground level.  I can just see myself using a reaching stick or chase cukes, tomatoes, and melons at the top of the netting. 

Cantalevered trellis on my tabletops.  Top of trellis is about 6 ft off the ground.



These are just the regular emt trellises as shown in ANSFG book, but the rebar is set at a 45 degree angle at the front of the bed and held to the sides of the back of the bed with u brackets. Gives me about 6 ft of growing space on 3ft high tabletops without having 10 ft tall trellises. You may still need a stool, but you won't need a ladder.

Kay

Tomorrow I'll put the finish touches on the bases of my raised SFG boxes. I still have to fill in the bases with more sand and river rock. The actual boxes are 8" high boxes that will screw into the wood frame. I need to get tap cons in the morning to secure those frames to the cinder block. We've got a ton of river rock to haul tomorrow afternoon. Anyone want to help? 

Oh, and I consider the bases the coffins of those nasty root knot nematodes. I'm DONE with them!  ...at least in that part of the garden.

Looking great! 

Wow, don't think I've seen such skinny cinderblocks before.

Marc Iverson wrote:Wow, don't think I've seen such skinny cinderblocks before.

Yes, these are 16"x8"x4" and can be found at Lowes or HD.

Got these bases built this weekend. I just want to add more sand and have a layer of river rock with weed mat underneath. The weed mat is not necessary for weeds, but because I'm a bit paranoid of the root knot nematode infestation contaminating the boxes.  Yes, I'm sure they can go though weed mat, but why would they when the sand is clearly separated from the rock? That's why I mined for the virgin white beach sand which can be found 1.5' down just about anywhere on my property. 

I've got more center supports to put in and I'll probably pour a little Quikrete foundations for them to keep them from sinking under pressure. 

The actual SFG boxes with 3/4" plywood will screw into the wood frames you see. I've got my drainage holes drilled and will screw in some screens from our old windows. 

I can't wait to get my seedlings planted!!!

Got any feedback?

Or remove the wood trim, pour Quikrete now, water it, level it with a screed leaving a slight drainage hump in the middle.  Like 1/2" drop / 2-4 ft run.  Then you can set the wood frames directly on the cinder blocks (or are they called cement blocks there?) and forgo the plywood.  Maybe a clear plastic sheet on top of the Quikrete is better, all the way to the outer perimeter.  Since the cement will be fresh, it can leach out lime so the solid plastic barrier will keep it from the MM. Then set the frame on the cinder blocks and plastic.  Mel states you can set an open or closed bottomed box directly on cement patio.  Those wood trims? They can be used on the top of the wood box as decoration.

Or go with the idea you stated below.  Since you are using Quikrete, just make sure water can drain to the edges by making a hump in the center.

I just like to KISS.

Regardless, you are doing an awesome job protecting against the nematodes.

Have you looked at concrete sleepers that do not rot .

I vote for sanderson's idea. (again!   )  Mainly, because I don't like using plywood where it remains continually wet.

I'd compact the sand with water or mechanical means, and then pour approx. 2 inches of concrete.  Rather than worrying about pitch for drainage, could you use pipes,  with screens on the ends, through the concrete to drain into the sand?  (I don't have a clue if the screen would stop root knot nematodes.)

sanderson wrote:Or remove the wood trim, pour Quikrete now, water it, level it with a screed leaving a slight drainage hump in the middle.  Like 1/2" drop / 2-4 ft run.  Then you can set the wood frames directly on the cinder blocks (or are they called cement blocks there?) and forgo the plywood.  Maybe a clear plastic sheet on top of the Quikrete is better, all the way to the outer perimeter.  Since the cement will be fresh, it can leach out lime so the solid plastic barrier will keep it from the MM. Then set the frame on the cinder blocks and plastic.  Mel states you can set an open or closed bottomed box directly on cement patio.  Those wood trims? They can be used on the top of the wood box as decoration.

Thanks for the suggestion Sanderson. I may try your suggestion once the 3/4" plywood (that I've already bought and drilled holes) has rotted in 5 or 6 years. By that time I'll probably need to build new boxes anyway.

sanderson wrote:Regardless, you are doing an awesome job protecting against the nematodes.

I've done quite a bit of reading up on nematodes and I've even solarized some of the infected areas. So I know nematodes don't do well in organic matter, but should I be concerned about contamination in my homemade compost mix? I read that they have been known to survive the compost process. I'll be devastated if my boxes get contaminated after all of this work.   That's the main reason why I'm concerned about the cats getting in the boxes.

Dstack,  Have you discussed nematode control with your Country Ag Commissioner's office?  I assume you did as part of your research.  I did a quick research and found an article by UC Davis in CA for solarization.  So it does work but only for shallow soils, it seems.  Like the depth of MM!!!!  Yeah!

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74145.html

Well, here's my two cents, for what it's worth:

So, solarize your new filled beds for 4-6 weeks before planting. Build a way to solarize the compost that you will use when replenishing the squares at re-planting time.  Compost on 4 mil plastic sheets or clean barrels.

Question:  Where have you been storing the plywood?  A clean place? I don't know why I'm hesitant about using it on the concrete beds.  I'm afraid that there will be low areas in the cement bed where water will pocket, creating little septic areas. (like when I put my pots in trays!) You can use the drilled plywood for small raised beds on cinder blocks, like for a small salad bed; top hat height for long rooted carrots, parsnips,etc.; a separate potato bed.  Things that would call for separate or modified beds, anyway.

Regarding the cats, use metal electrical conduit as though you were building trellises, but they can be shorter, like 2' tall, on the other 3 sides.  Secure bird netting on these 3, using zip ties.

Keep us posted.