I want to make frames for a raised bed garden. I have some pressure treated wood but I’m concerned about the toxic properties migrating into the soil and plants.
Should I use non-PT wood or even composite decking material.
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The objective analyses done on that scenario indicate that even old arsenic-treated lumber would not be a problem, and the newer stuff less still.
white oak"this dog may be old but he ain't cold. And he still knows how to bury a bone."
Lattimore
http://www.rehmodeling.com
The best raised beds I've tried used old cases from refrigerators or freezers.
After having some redwood raised beds for a few years, DW deceided she liked using large plastic post better, but did keep 2 of the old freezer box raised beds.
What DanH said. I and many others have ACQ raised beds. They work very well (although you need to be careful about what fasteners you use).What "toxic properties" are you concerned with?
Scott.
I didn't use PT because I'm a chemical freak. Considered PVC momentarily (and for planters--the gluing possibilities!) but ruled it out cause the chemicals seemed even worse. I'm using culls from Ipe deck projects in the back. 5/4 can go 6 feet easy, just fastened in the corners. I'm playing with some 3/4 this year as well, and suspect it will do just as well.
I started using 4x4's in the corners to assemble, but ran out and used some 1 1/2 x 1 1/2 baluster material, pre drilling and countersinking deck screws, which I plugged. Pretty and pretty rugged.
Micronized copper does have the potential to cause concern depending on how finicky the Gardner is about their crop and how sensitive the plant species in the boxes are to nutrient soultions. Reason being that copper is actually used by plants in trace amounts and is listed as a micro nutrient on many fertilizers. Too much copper present or existing combined soil conditions the copper can have the ability to lock out the up take of more heavily required nutrients by the root system of the plant. To an untrained eye the results may appear to them that the plants just need a dose of fertilizer, only worsening the problem. Than looking as if the plant just needs water and now their drowning the roots on top of it. For most people with some unattended summer time peppers no worries with the above.
I remember when the scientists said - no problem with the pressure treated; then, they started to find out how much it leached. All of a sudden, nobody likes arsenic in their soil and you can't buy it.
I prefer to use untreated materials. I'm getting a small load of cedar logs - actually, the outside since the middle was already cut for lumber. I'll buuild raised beds with them. If I need to change them in three years, so be it. If you want something really durable, try concrete, or build the beds using berms and sloped sides.
Many people disagree and claim that the chemicals we use daily in such small amounts are meaningless. I look around at so many people getting cancer and I don't agree. Rather go with the old style - FWIW.
Don K.
EJG Homes Renovations - New Construction - Rentals
The elimination of arsenic-treated lumber had much more to do with politics and emotion than it did science.
The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith
you could use that high dollar pvc deck looking wood at lowes
IIRC, and I'm no chemist, it's actually Copper Chromium Arsenate. The "nate" turns to "nic" when burned in a fire, and there were some health issues with people that didn't know any better and tossed a bunch of PT wood in the campfire. Nonetheless, CCA lumber has no arsenic in it as long as it's used correctly. But like you said...people get their emotional panties in a knot....Scott.
"Copper Chromium Arsenate. The "nate" turns to "nic" when burned in a fire,"Heat or acid released the arsenic from compound.
Acid rain, acid soils, acidic stomach where kids chew on it....
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I also suspect that the manufacturing process for CCA was less than green. What happened to leftover chemicals, trimmed mill ends, etc?
A lot of that emotional politics came from people using PT inappropriately in things like gardens and playground equipment. you should be more carefull advising on something like this that can hurt folks health.
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I seriously thought about concrete as well, but don't have a mixer and the truck is a PITA around here. When I was at the soil place I saw some rough gauge bluestone that was pretty cheap--and I left lots of open spaces for herb and flower planting.
I second---------White oak
There's a big difference in the potential exposure based on what you're growing, and how close it is to the bed edge. Root crops planted close the edge are more likely to bioaccumulate toxins than flowering crops planted in the middle. That said, there's been some research out there that showed poppy flowers bioaccumulated heavy metals at a very high rate - they were testing it as a brownfield remediation tool.
The science around the raised bed/treated lumber issue is sketchy, I've read very little that didn't raise more questions than it answered. However, most studies seem to at least agree that toxin levels drop as you get farther from the edge. Duh!
I bought some "xpotential" timbers about eight years ago. They're an ugly synthetic made from ground up cars, recycled fiber and plastic. Rated for 100 years continuous ground contact. Absolutely no science out there to say if trace organic polymer, etc.. exposure is any better or worse for you than trace metal exposure, so it's hard to call it a solution. And boy are those suckers heavy!
If you have enough room, you can just make raised beds without borders. If you lay out your paths well, the dirt stays up pretty good.
I've also noticed that plain old hem/fir does a decent job for about 3 - 4 years and a half-ssed job for 3 or 4 more. Not such a bad option, really.
I've been building my beds out of corregated steel roofing. They can be painted or left metalic in color. Redwood 2x2s make up the corners.
Here's some info on that from my Hoophouse thread:
http://forums.taunton.com/tp-breaktime/messages?msg=104597.27
Good old Douglas Fir. Pick through the pile and find some good, dense boards with no sap wood. Sure, it will rot eventually but by the time it does, the soil will be well trained and won't go anywhere.
A garden for food production is the last place in the world you want to use PT lumber. the acids in manure or other soil additives can leach the toxins out of the wood and into the soil so that you end up eating carrots with unsafe levels of copper and/or arsenic.
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The acid levels required for leaching arsenic are pH of 3 and below, too acidic for even blueberries. Acids forming in the composting process tend to be more active, but finished compost is a neutral pH and not a problem to add to beds. Just don't use PT on compost bins.If you're still worried, you can peel your veggie roots. It's the dirt still attached that has the most arsenic in it. Plants take up very little arsenic, and much of that is background levels in the dirt irrelevant to PT lumber use. Most of it stays in the roots, and even in root crops, it's in the tail end that is normally discarded.The chemicals can leach with water for a short distance, but if you keep from making toothpicks of the stuff, you're relatively safe with PT lumber compared to the other hazards of living. For anyone contemplating forming concrete, be aware that the alkaline content when it's fresh can be very detrimental to plants.Incidentally, the community gardens i'm involved with used <shudder> railroad ties for raised beds. In addition to being butt-ugly, the creosoted, oak ties are mostly rotted through after five years, although the gardens weren't used/watered for the last four years. Dirt is just darned hard on and wood, and untreated wood will decay in no time at all. CCA and ACQ wood is all i've found to hold up to warm, wet dirt. If i were rich, i'd go with concrete, though. My next-year's project for the Community Gardens...
I'll stay safer and keep all the arsenic out of my beds.Funny how I am looser than you on asbestos but stricter on arsenic.Tho I am aware that arsenic compounds do have some health benefits, and I eat apple seeds and other pits that have arsenic.;)intersting note - Wife tells me that they used to use arsenic for embalming, and that the old cemeteries are leaching it into the ground water. She is head of cemetery committee here and gets specific articles on this stuff.daughter and her beau have just drilled a well and that property borders a 300 YO cemetery. Guess how the water test came back?!They have to do a reverse osmosis filtration to be able to drink or cook with it.This well is about 300 feet deep. So much for arsenic not traveling far in the soil.
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<<Funny how I am looser than you on asbestos but stricter on arsenic.>>That's because my opinions are based in science and reasoning! 1 in 200 beds in the UK occupied by men dying from asbestos isn't a hunch; it's a statistic.When we're talking about PT wood, a specific kind of arsenic, introduced into the environment, is in question. As i stated, there is a certain amount of varying inorganic and organic arsenic that is already in the soil. The kind that was used in CCA wood doesn't appear to pose a problem, nor leach very far.As to cemetaries, i did some reading and it said up to 12 lbs. of arsenic would be used in a body. Ayuh...i could see putting a bunch of those in woden coffins in one place might cause trouble. However, the similarity between PT wood and hundreds of pounds of embalming fluid hitting an aquifer 300 feet down is flimsy. As to that well water, there is a very high background amount of naturally occurring arsenic in your area, according to the USGS:http://www.boston.com/news/local/massachusetts/articles/2005/01/19/concern_mounts_over_arsenic_in_wells/"A recent US Geological Survey study found that arsenic is far more widespread in private wells in eastern New England than previously thought. While scientists have known about the prevalence of arsenic in the area for more than 20 years, they have now clearly defined an "arsenic belt" linked to geological formations stretching from central Maine through northeastern and Central Massachusetts."So...who ya gonna sue? <G>
Is it not Cyanide in peach pits?
where you getting the arsnic connection?Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations
"If Brains was lard, you couldn't grease much of a pan"Jed Clampitt
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article I read ten years back focused on food that have arsenic.Said common in apple seeds, and trace often in apricots and peach.I think some of the reasoning was that Mother Nature is protecting the next generation from insects by adding a bit of toxicity to seeds.
You are right on the cyanide. That is the Laetrile.
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Ok, now I'm really crossed up..Laeatril is a heart/blood med?
I'm also thinking that Warfarin ( an anti coagulant, from my PCO days) is an organophosphate derived from common food goods.
I know it makes rats get flat real quick like.Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations
"If Brains was lard, you couldn't grease much of a pan"Jed Clampitt
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Nope, it's the cancer treatment that never got FDA approval. Folks had to go to Mexico or Europe for it. Chemical compound derived from apricot pits - it contains a form of cyanide.Interestingly enough, chemotherapy is essentially poisoning you enough to kill the cancer with controlled dosage just low enough to not knock off the patient. Lots of Chemo has an arsenic compound in it.Almonds are related to the pits in peaches and apricots, and there has been a semi-controled study indicating that eating ten almonds a day is a darn good preventive for at least one kind of cancer. Forget which.
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Thats right, thanks for the brain start.
Rose had the ovarian cancer, and i got cornfused w/ Coumodin which was a blood thinner.
Ya know, I eat a lot of nuts, esp in autumn and winter, I must be part squirrell...maybe I can avoid the big C?
I have a prostate issue now, I'm 48 but the Meloxicam for my back spasms is playing hell with the prostate and kidneys.
BTW I recall you have fibromyalgya? This Meloxiicam is great for the general inflams, 7.5 mgs a day, VS tons of Aleve or Vitamin I..but the kidney/prostate issue is bothering me, and another side effect is my semen is ....wait, I'll email ya if ya wanna know.
You are past making babies I think.Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations
"If Brains was lard, you couldn't grease much of a pan"Jed Clampitt
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Forgot to mention.I have 6x6 cedar beds in front of the house that are just over ten YO and ready to rebuild this year or next, and this is a wet climate.The ones I built for tomatoes and such last year are three year old 6x6 spruce ( because I had them for cribbing and I intend not to do any more of that sort of work) 30" high. I lined them with some left over drainage mat for foundations, so that will be an interesting experiment in longevity.
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Interesting about the drainage mat...good experiment. Roots might dry out a little faster, is all. I should do some experimenting with different species of wood to see how long they last, buried. The thing is, the wood lasts bec it's already carrying it own toxic mixture, ready-made...
Someone mentioned concrete.
I made some forms, about 2" thick and 12" high.
After I pulled the forms I mixed some carbon black with portland and sand and troweled it on as a thin veneer to add color and a bit of texture.
These beds have been going strong for about 7 or 8 years.
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Did you use fibers, re-bar or ____ for reinforcement?
No reinforcement at all. I thought with them only being 2" thick and having moist soil on one side that rebar might have caused iron staining, or possibly even spalling. I came so close to inserting pieces of hardware cloth, maybe 10" tall by 20" wide, bent to follow the angles at each corner, but never bothered.If the soil was unstable in the least bit; uncompacted, expansive, unstable, for me the hardware cloth would have been required.
That looks very nice... clean and elegant. My wife and I have talked about this sort of approach - we'll be adding this pic to the project folder. Project #1276...I can't tell from the pictures, but did you go to any great lengths to crown the top, or did you just roll the corners?-t
Thanks!The top edges of the concrete beds are pretty much flat. The edges are just rounded over a bit. I didn't go for perfection with the carbon black veneer, I wanted something a little more rustic. I wanted some trowel marks and some imperfections in the surface. Next step on my "to do" list on that garden is putting bluestone down over the compacted stonedust that's there right now. Those concrete raised beds work quite well. I've done them in a couple of other sections of the yard too. Matter of fact a couple of posts ago I posted a photo of stacked wood raised beds. That was supposed to be concrete like the other photo, but my wife actually wanted something more rustic, thus the wood. When the need arises I'll replace the wood with concrete.For the concrete photo that I posted, I made a single set of forms for a single corner of that garden. When the 'crete was cured, I'd strip the forms, screw them together again and put them in the next corner. One set of forms was rotated through the four corners.
ya don't need to be rich - just energetic!
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Edited 5/15/2009 12:35 am by wrudiger
You know, i was thinking about that technique, too. I will ask if the school has a pile of busted-up concrete somewhere. The school is allowing our gardens to be on school property, near their boneyard, as luck would have it. I can have stuff that they've dumped out there, so there's a large monkey bar thingamee that is going to make a fabulous entryway covered with climbing roses. And i have mounds and mounds of grass for mulch!
>...pile of busted-up concrete somewhere.<
If you can get to the CC before they break it up, you can get it cut up into manageable slabs and stack/set them accordingly.
I like that idea! I have an acquaintance who finishes concrete...i'll talk to him and see if he knows of any demo jobs in the offing. I can give a charitable-donation receipt from our non-profit, maybe make it worth their while to accommodate. Good idea, John!
jsut something I've seen a few times.
On a small scale Dad has cut up several sidewalks and the slab from his old shop and used the pieces as a retaining wall, IIRC his were ~16"x~6' and were easily moved with a hand truck and him being the only labour.
On a large scale DOT contractors during 12hr lane closures (nights & weekends only in the metro ATL area) cut and remove slabs of the interstate for localized repairs. The slabs (one lane wide and ~10') long are lifted with a special fork attcahment on an excavator and trucked off site to be broken up for fill.
...covered with climbing roses."
My favorite climber is a Davis Austin rose, New Dawn. I'm not a big fan of "pink" pink, but this is a very blush pink, more peach/cream, with a wonderful fragrance. Vigorous. Hardy. Easy to propagate.
My highly technical propagation methods are to 1) take 18" length of canes that I cut off in early spring cleanup 2) use a piece of rebar to punch a 12" deep hole in the ground 3) pop the cane in the hole and stomp the soil around it with my foot.
Here's New Dawn on my pool fence and pergola:
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Below is a half-season's growth of a vigorous vining flowering climber, Silver Lace. I started these early last summer, these photos were taken after one season's growth. In the foreground one vine (non-rose, just a flowering vine) is growing up and over the arched garden gate, in the background another is growing up the other side of the pool pergola opposite New Dawn.
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Thanks for the info on the formwork. I was also wondering how steel would act only an inch from the surface, but hardware cloth would be a good alternative. I'd probably go a little thicker, just bec it's a public place that will get more use/abuse. CT would have a milder climate than MT, but that's the look i'm headed towards with the arbor. I'll try to find a nice arbor locally with roses and talk my way into getting some starter canes. I thought first of grapes, but the liability of monkey bars/grapes made me blanch, so roses it is. I'll check our the "silver lace", too...hadn't heard of that name except applied to artemesia (sage).I'm heading into Missoula today to collect the watering system partz...first things first, lol...
Checked my notebook, this "silver lace" is "polygonum aubertii". Listed to zone 4. I'm 6b and got some very minor winter dieback on some parts, which is to be expected. My notes also say that it can be completely cut back an mulched over in the fall and it'll run wild the following spring.One of those "vines" that I'm sure can also be described by others as a "weed"! Vigorous.
Those 'weedy' vines....i nurse along Virginia Creeper, lol! Cutting your Silver Lace to the ground each year and mulching might make a nice, low hedge for me, if i were lucky. It snowed last Tuesday. I looked at the size of the seedlings in your beds (if that's a current pic), while i still haven't planted my hoophouse with tender plants yet. Cabbage-under-glass is all i can manage thus far. We're Zone 4, mostly, with some real micro-climate issues bec of the mountains. We had -19 for a while this winter, and i STILL have a field of damned grasshopppers i'm bombing this year with Nosema locustae, my version of bio-warfare.Your gardens exhibit your trademark planning and taste. I always enjoy your construction threads and pics, but your green thumb is a sweet surprise.
You're so kind, thanks.Those photos are from last year. The New Dawn in mid-June, the Silver Lace in mid-August. I really enjoy landscaping and gardening. I've always had a give-and-take with nature until a couple of years ago when woodchucks and moles/voles just destroyed years of plantings. I finally had to go Carl Spackler on them.I'm in recovery mode now and probably through next year, propagating and replanting.
Carl Spackler...had to google it. Someone gave me that movie a long time ago hoping to improve my Slapstick Quotient. I'll have to give it another chance, being that's the umpteenth Caddyshack reference on BT lately.At least i don't have to be chagrined that your 'maters are knee high in mid-May. Today i spent a couple hours in HD pulling together an irrigation system for the community gardens for about $430, all drip system and electronic timers, a faith-based initiative conceived in freezing temps and dedicated to the proposition it can't snow forever. The prequel to this go-round failed and languished four years bec my progenitors had the ludicrous idea they'd haul water or run hoses a couple hundred feet. I don't mind shoveling for hours at a time, but i'd rather be flogged with a Skidoo track than stand with a hose in my hand.
I have to admit I couldn't remember the character's last name so I had to google it myself.Are you doing drip irrigation? I threaten to layout and install a system every couple of years, then I sit back and nap when I realize there are still myriad hardscape projects that I'd like to accomplish prior to going with drip.I refuse to water any landscaping plants, perrenials, flowers, rosebushes, even my grass, etc, unless I'm getting them established. They live or they die.My veggie garden? I do water that on occasion, and I'd like to do irrigation on that one day.I'll think about it...tomorrow. <sigh>You're still getting snow? I best not tell you that I opened the pool a couple of weeks ago and went swimming today...
After i set up my hoophouse last year, i laid out drip lines, then mulched. I pretty much just turned on the [mechanical] timer and hacked back the vegetation to leave a path between beds for two months, then i harvested...and harvested...and harvested. The shelter, the watering, and the mulching worked synergistically to make last year's effort such a screaming success with so little maintenance, but the regular watering with drip irrigation was the most salient change from a much smaller HH i'd experimented with prior to this. HD had a surprisingly good selection of drip irrigation stuff this year, and better prices than Lowe's, which hardly ever happens. I was set to order from mrdrip.com, the best web source i've found, but i lusted for immediate gratification. If i were a saner person, i'd buy the hose at HD to save on shipping and the fittings at mrdrip.com for price and selection.I tried molded-in emitters in 1/4" line last year, which i expected to clog with my hard water, but i was pleasantly surprised how well they worked. You can get the molded-in emitters on various centers from 6" to 36", and at various gallonages per hour at various psi's...lots of choice how to approach a problem. I also tried the drip tape last year, which i simply poked with a T-pin to make spray hose for the row crops like carrots. Those holes would close up and i'd have to poke it again every couple of weeks; i wouldn't recommend that.I picked up some .700 hose at HD with emitters in it today. I've never tried the larger dia. with emitters yet, so i'll give it a run on the maters and cants in the HH. I've used drip buttons before but they fall out and get broken and silt up and are a general PITA. I'd avoid buttons unless your spacing requires it. Soaker hose works well only if you have soft water. I use mine like solid pipe now it has a mantle of deposits inside. :^( Snowed at 3600' this week. It's not sticking down here, but still...
I was looking through photos files today and something made me chuckle. Remember your comments about how you like my color choices inside the house?
Well I'm just about the polar opposite when it comes to the outside my house. When I put my pool in I wanted the anti-california pool. I wanted dark plaster, gray slate on the waterline, stone patio, and stonewalls, and weathered cedar fencing. Subdued grays and other assorted blah neutrals.
Outdoors I prefer muted neutrals in the hardscaping and I prefer the punches of color to come from the plantings.
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Yup, i noticed the neutrality of your outdoor palette compared to indoor, and now i notice you varied shapes instead of color, e.g. the retaining wall has the same tones as the slate, but different outlines. I've been reading a book on neuroscience about how eyes select an outline of an object, which explains why cartoon drawings are intelligible for us. Anyway, now i notice outlines more than i used to. About that boulder retaining wall; are the rocks cemented together or just battered enough to stay put? I like color EVERYWEHRE, so i'm fixing to do the rainbow scheme on my second HH's ribs as soon as it's warm for a whole day. I bought a special pipe-painting roller just for the job this time; i used enough spray cans last year to break off a couple square miles of the Arctic ice cap.
The stone walls are all dryset, no mortar. Between clearing the building site, excavation, and tilling the areas where I wanted to establish grass lawns, I had piles and piles of stone stacked in the woods.
It's all round glacial rock, so battering is a necessity with this stuff. I have several hundred feet of roughly 24" tall retaining walls. Some days I'd stare at the stone in bewilderment and surrender after struggling to stack a few feet of wall. I remember one other day when clarity finally visited and I did 60 feet of wall in what seemed like no time at all.
Below: A blurry photo, taken at a 90-degree turn in my driveway. From where I stood to take the shot the driveway extends to my left about 750' out to the street, then in the direction the camera is pointing, another 120' or so down to the parking apron at the house. You can see the degree of slope on the face of the stone wall on the right edge of this portion of driveway.
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Drip irrigation, good info. I've been leaning towards inline emitters. Time to study up again.
I know those moments of clarity when it all falls together almost in spite of one's consciousness getting in the way. I was so excited to read Malcolm Gladwell's book "Blink" on that very idea. I invented a phrase when i was a kid that "intuition is logic at lightning speed." It looks like there's some validity to the idea, but getting it to work means loosening up more than is comfortable at times. I really like how you used native materials, spinning straw into gold. At my last house, i battered the walls leading away from the walk-out basement with glacial boulders from about 16" and down. I was on clay there, so i picked and hauled load after load of stones from nearby fields whose owners were tickled pink and purple about it. I placed them on old carpet for weed control, then filled the spaces with sewer rock, 1-1/4" minus. The only thing i paid for was a load of rock and some moleskin...smack in the middle of my price range, lol. I kept a gravel driveway, too, so the whole effect was as close as i could get to "Zen rock garden" on a rancher in the midst of sagebrush. Sorry, no photos; that was in the pre-digital age and they're "archived" in a shoe box somewhere. The new owners ripped it all out (along with the French drains to daylight i'd dug by hand...oops) to pour vertical, stepped, gray concrete walls. I'd have liked to salvage the many loads of rock, but they dumped them on the septic field to build that area up. The next time i sell a house, i'm moving farther away so i don't have to look!
What kind of fuzzy biscuit junky is that hiding back there?
That walking fur bomb is Nikki, our 12 yr old German Shepard
Her coat looks like a much younger dog.
Her coat looks like a much younger dog.
That's cause she's constantly replacing it - LOL! She is a good looking dog, no arguement. Very well behaved also; no concerns with young kids - she will just get up and walk away if they get too unruly.
A bit camera shy tho...
I built about 150' of raised beds for customer years ago who was worried about PT leaching so we lined them with 6 mil polyethylene stapled in place
the client is a plant freak and has never said a thing to me since and i was there the last couple of days working
the origional beams were cedar and dident last worth a sh**
Arsenic can be found in fertilizer at retail...no disclosure required. Ironite is one found to contain extraordinary levels of arsenic bec it's sourced from the tailing of an old mining operation.
Mahogany =)
~ Ted W ~
Cheap Tools! - MyToolbox.net
See my work at TedsCarpentry.com
Here's one other photo that I have, these are crappy "landscaping timbers" (ha ha ha), pressure treated, about $3 each at Ring's End. Not sure where you are in CT, but there are several RE yards in the state.
These are stacked with a slight offset inwards and simply nailed with 20d spikes. I then "painted" the soil-facing side with roofing cement and let it cook in the sun for a few days.
The overhead support structure is leftover cedar from my fence.
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I used rough-sawn 2x12 hemlock. It will only last a few years at best but I'll probably want to change the layout by then anyway. It's cheap, doesn't irritate like mahogany or cedars, will last longer than pine or spruce. I have no interest in using plastic or PT in the garden.
Next time around I might try masonry walls. Or, no walls at all, just mound the beds, which will work especially well if I get around to laying bricks between the beds I have now. Then I can just eliminate the beds and use the brick pavers as borders.
I use rough spruce or hemlock or whatever the local mill has. 2-2x10 x 16 feet makes a 5 x 11 raised bed. I get a good five years or more before they need replacing and I don't need to worry about chemicals leaching into my rutabagas.
I agree but mine are 4 x 12, more or less.
I made them 3 inches shorter so that when they start to rot, I can put the new ones around the old ones.
I used red oak 25 years ago and it lasted 5 years. I`d use locust if it`s around your area. Locust posts last 50 years in the ground. See if there`s a sawmill around.The time & labor to make rased beds ,you only want to do it once. Double dig & add compost.
Why not granite curbing? Beautiful, last forever, no maintenance, no chemicals. I am finishing up one now for a school around a greenhouse. I got the curb for $10/foot. This job is 425 feet. Pictures show granite down, but not mortared or backfilled. Nice old curb would be better, but a lot more work on a job this big.