After 14 years using the same cedar raised beds in my vegetable garden, the time finally came for a garden makeover. In this week’s podcast, I’m sharing how I applied the experience I have gained in this garden to decide what to change during my garden rebuild and what to do exactly the same.
The garden here on the GardenFarm™ outside Atlanta includes 16 raised beds. I have been putting off the redo because it is a huge undertaking. But it has also presented an opportunity to bring you behind the scenes and share tips you can use for your own garden makeover. I even held a 90-minute live Q&A to address your questions, and you can download The Complete Guide to Building Your Own Raised Beds to learn how you can replicate what I did.
Me and my brand new raised beds. They are only missing the soil — and seeds and plants.
My garden’s footprint is about 75 feet wide and 45 feet deep. If you have followed me on social media or watched my public television program “Growing a Greener World,” you’ve seen the raised beds that I installed 14 years ago, each one made with big, chunky, untreated cedar timbers. It was gorgeous then, and remained gorgeous, but over time, the timbers rotted. Because they are untreated, there is nothing in the timbers to preserve them other than the compounds naturally found in cedar.
Things started to give way by year 10. Over the last three to four years, I knew that the raised beds were on borrowed time. It was inevitable that at some point I was going to need to take those beds out and replace them with something. Well, that time came in the last couple months.
The beds were literally falling apart, and I knew they didn’t have another year left in them. I had gotten all I could out of them. Termites combined with the heat and the humidity, plus the moist soil in contact with the wood at all times, did the beds in.
The cost of cedar timbers has tripled since I installed the beds, and they were expensive back then too. Redoing the beds with cedar timbers was out of the question. In fact, any hardwood timbers of the size I need would be hard to find and prohibitively expensive if they could be found. It would have been a $25,000-$30,000 project to repeat what I had done 14 years ago.
My cedar raised beds truly did not have another growing season left in them.
Making Changes While Maintaining the Feel
I have a preferred aesthetic for my garden. It fits in nicely with the house, barn and greenhouse. I wanted to stick with the natural, somewhat rustic look.
Something completely different, such as cinder blocks, stones, or modern rounded all-metal beds were not going to work for me.
The installation of the original, cedar timber raised beds. I did not want to stray far from this look and feel.
A few episodes back on the podcast, I interviewed Gardener Scott of Colorado. He trials and builds out all kinds of raised bed examples. On the cover of his book is a picture of a garden with beds that were very much what I had in mind: a combination of wood and corrugated galvanized steel.
My friend David Park out of Nashville, Tennessee, heard on the podcast that I was planning to replace my raised beds. He has a background in design and is experienced with CAD software. Out of the blue, he sent me a mockup of me in my garden with new beds — beds just like the ones I was envisioning. I was blown away, and I was immediately sold.
David’s rendering of my garden makeover
David refined the design to the Nth degree, including the number of fasteners we would need and the various wood we would need of different dimensions. Then he drove down and gave five days of his time to help me build it with my friend Pete Loughney of Michigan.
The beds include pressure-treated pine and galvanized metal panels. Both materials were produced with chemicals designed to make them last longer. Because I am an organic gardener, this seems counterintuitive, so a little later on, I will share my reasons for choosing these materials.
My friends David Park of Tennessee and Pete Loughney of Michigan gave their time and expertise to help make my garden makeover dream a reality.
Clearing the Deck for a Garden Makeover
Ahead of David and Pete’s arrival for a five-day build, I spent 10 days getting ready by removing the old wood and soil and clearing the deck.
Each bed was 12 feet by 4 feet and 18 inches high. That’s a lot of soil, and I had spent 14 years improving its fertility. However, over 14 years in production, with inconsistent crop rotation, the soil was also full of soil-borne pathogens.
I relocated the soil to another part of my property. You may be wondering if I am concerned about those soil pathogens making their way back to my garden, but I’m not. Consider the disease triangle. In order for a pathogen to infect a plant, three factors need to be present: the pathogen, the host plant that is vulnerable to that pathogen, and certain environmental conditions. It’s only when all three of those things come together and align perfectly that an infection actually takes place.
I placed the soil in my native plant beds, where I am not growing any plants that are vulnerable to the same pathogens that infect vegetable plants.
The cedar timbers, I held onto. I will add the chunks of this untreated organic material to the new beds. As the wood breaks down, it will enrich the soil, in the style of a hugelkultur garden.
The cedar timbers after being torn out of the garden. This is untreated wood and valuable organic matter. I will reuse it inside the new garden beds to feed the soil.
Modern Treated Wood Doesn’t Raise the Old Concerns
Back in 2003 or earlier, I would never entertain using treated wood for a garden bed. But things have changed.
Prior to 2003, treated wood included arsenic, which I’m sure you know if not a friendly chemical to have in your garden, or anywhere for that matter.
Chromated copper arsenate, or CCA, is the pesticide that was widely used as a wood preservative. It’s nasty stuff. Back in 2000, the industry agreed to cease using CCA in the consumer market.
Copper has replaced arsenic as the primary ingredient in treated wood. Copper-treated wood may not last as long as CCA-treated wood, but it outlasts untreated wood. And I’d take wood that doesn’t last as long over wood treated with arsenic.
Oregon State University conducted a two-year study of copper-treated wood in gardens and found that there was no increase in copper concentration that was detectable in vegetables.
Treated wood garden bed material increases copper concentrations in soils within 25 millimeters of the bed edge by a factor of only 20 parts per million, relative to levels measured in untreated garden boxes.
Metals are more migratory in soils with a low pH, below 6.0 or 5.5, which is quite acidic. A productive vegetable garden is closer to the range of 6.5 to 7.0 — closer to alkalinity. The metal chemically binds to soil particles in soil that is close to alkaline, so if you have good garden soil.
Pine treated with copper is not a health and safety concern like CCA-treated wood of old.
How to Safely Seal Cut Wood
Treated wood has sealed edges, but if you cut that wood to the size you need, the wood now has exposed edges. Putting those exposed edges in direct contact with soil will accelerate decomposition. So David, Pete and I treated all cuts with Garden Box Armor, which is nontoxic and includes only plant-based preservatives.
Using Galvanized Metal in a Raised Garden Bed
I looked into galvanized metal in gardens and found that health concerns are unfounded.
The consensus on the safety of galvanized metal for gardening is based on scientific understanding of zinc, toxicology, soil chemistry, and data from environmental and agricultural agencies.
These sources include numerous U.S. university extension programs, including Iowa State University extension, Purdue University Extension, and the University of Vermont Extension, along with scientific and government agencies with research supporting this safety assessment. And that comes from various sources, including the National Center for Biotechnology information, the Journal of Environmental Quality and the FDA, which permits the use of galvanized steel for food handling, excluding highly acidic food.
Galvanized metal is widely considered safe for use in raised beds, and the risk of harmful metal migration is extremely low under normal gardening conditions.
Zinc is an essential micronutrient for both plants and humans. And while it can technically leach into the soil, it is generally considered negligible. Zinc coating breakdown and migration is most likely in highly acidic soils, typically below 5.5 pH.
You are likely exposed to more zinc through standard tap water, often delivered via old galvanized pipes than you would ever receive from vegetables grown in a galvanized bed.
Regarding other metal exposure such as cadmium and lead — while trace amounts of other metals like that were once more common in older galvanizing processes, modern quality galvanized steel is produced to standards that make this risk minimal for home gardeners.
Corrugated galvanized metal will outlast wood and is safe around food crops.
Do Metal Raised Beds Heat Up the Soil?
One common question I have received is whether metal beds will heat up the soil to the detriment of the plants.
My friend Lisa in Australia works in a nursery that sells many metal raised beds. She says that never, in all the years that she’s worked there, has anyone complained about the heat. She says that though the weather gets very hot where she is, heat from metal beds is just not the issue that people seem to think it is.
Back in the United States, this question has been tested by various researchers. The soil right next to the metal and near the surface measured as hot as 97° Fahrenheit. Moving just slightly away from the metal, the soil was only 89° — an 8° difference.
So don’t plant right up against the surface, and there will be nothing to be concerned about. If you live in a colder climate, you could actually use the warmer edges to your advantage, sowing some crops earlier as the soil warms more quickly in spring.
Roots will spread out toward the metal sides of a raised bed, but they will avoid getting too close to excessive heat. Root growth responds to favorable and unfavorable temperature conditions. This is known as thermotropism. When they grow toward a temperature situation they favor, it’s called positive thermotropism. When they grow away from something because they don’t favor the temperature, it’s known as negative thermotropism.
So if roots are sensing that the soil temperature is too hot close to the edge, they’re not going to grow there.
Using mulch plus drip irrigation to ensure consistent, evenly moist soil will also cut down on excessive temperature concerns.
The shininess of the metal will fade naturally, or you could accelerate the process with certain chemical treatments.
Working with Corrugated Metal Panels
The 45 corrugated metal panels I bought for $29 apiece are 12 feet long and 26 inches tall. And they are surprisingly thin. When the delivery came, the stack of 45 panels was less than an inch thick. But the corrugation increases the stiffness of the panels, preventing any bulging.
To protect the pine framing from direct soil contact, which accelerates rotting, I cut lengthwise pieces of the metal and added those to the bottom of the interior, and married it in with the other panels. The corrugation humps and channels really line up nicely so they can just seamlessly connect to each other, and then you just screw them together.
I used a cordless DeWalt metal shear, which was really a must-have for this project.
A rendering of the garden envisioned during the growing season.
Why Hardware Cloth Is Necessary for Your Raised Bed Garden
Hardware cloth prevents moles from digging tunnels into your garden bed as they search for worms and other critters. Use quarter-inch or half-inch mesh — moles will slip right through a larger gauge.
When I originally built my raised bed garden, I did not include hardware cloth. Eight years in, I discovered I had a problem when I was hand watering and all of a sudden the soil began caving in, like a sinkhole. Mole tunnels were a problem for two years in a row before the moles moved on.
For the new beds, I staple-gunned hardware cloth to the bottom of the frames.
For a little extra money, I chose coated hardware cloth, which is dipped in vinyl to add to the longevity.
Add hardware cloth to the base of your raised beds to protect your crops from mole damage.
Keeping the Footprint
I have always loved the layout of my raised bed garden. I love the look of it. It had nice wide pathways going through the long axis, and one perpendicular wide path at the intersection. And in between the beds there was plenty of room for wheelbarrows and mobility.
In 14 years, I only once had a deer enter the garden — and I have lots of deer on my property every day. I attribute this to the layout. I had only 4-foot-high split-rail fences, and we all know that deer can walk over a 4-foot-high fence. But the layout of the garden made the garden appear an unsafe place for the deer to be and jump.
Deer like to jump straight over things, but they don’t like jumping long distances, like across a wide raised bed. The layout of the garden makes it unattractive to deer, as much as they would love to help themselves to my crops.
My garden makeover retains the footprint of the original design.
The Perfect Soil Recipe for Raised Bed Gardens
Another thing I am not changing is my perfect soil recipe. It worked so well for me, so why fix what ain’t broken?
The recipe is simple, and it starts with 50% high-quality top soil from a reputable nursery or landscape supply company.
Top soil should look like brownie mix: dark and earthy. It should not be red or gray, but chocolatey brown. No components should be recognizable. It should be so degraded that it all looks the same. It should smell rich and earthy, not sour or offputting, and it should crumble and break apart easily.
The recipe continues with 30% high-quality compost. If you have a small garden, you could use your own homemade compost. But if you have a large garden like me, you’ll need to have compost delivered. I am fortunate that here in the Southeast I can order bulk humus compost from Soil³.
The last 20% is organic matter, and there are several options to choose from based on the resources you have available to you locally: shredded leaves, worm castings, mushroom compost, aged ground bark, and composted poultry manure or cow manure.
To learn everything you need to know to make the perfect soil, you can enroll in my Perfect Soil Recipe Master Class.
If you have a small garden, you could use your own homemade compost. But if you have a large garden like me, you’ll need to have compost delivered.
Watering a Raised Bed Garden
When I created my garden originally, I needed an automated system for each bed because I travel often. No two beds are the same, and they have different watering requirements based on what’s growing there. So each bed got its own spigot that I could attach drip irrigation or soaker hoses to.
I haven’t used drip irrigation as much as I thought I would. For years now, I’ve been hand watering with my watering wand. I’ll stand there over those beds and water at the soil level, and that gives me a great opportunity to inspect plants and make sure they’re looking healthy.
A drip irrigation system in my old garden beds.
I hope you enjoyed joining me on my garden makeover journey. If you haven’t listened to the podcast yet, you can do so now by scrolling to the top of the page and clicking the Play icon in the green bar under the page title.
Have you been through a garden makeover? Let us know what you learned in the comments below.
Links & Resources
Some product links in this guide are affiliate links. See full disclosure below.
Episode 042: Raised Bed Gardening, Pt. 1
Episode 043: Raised Bed Gardening, Pt. 2: Perfect Soil Recipe
Episode 044: Raised Bed Gardening, Pt. 3: Animal Control & More
Episode 213: Understanding the Basics of Hügelkultur, with Paul Wheaton
Episode 416: Raised Bed Gardening, with Gardener Scott
joegardenerTV YouTube: Major Garden Makeover: Removing Every Bed & Starting Fresh
joegardenerTV YouTube: Why I Tore Out My Raised Beds and How I Rebuilt Them to Last
joegardenerTV YouTube: Live Q&A: The Raised Build Garden Rebuild!
joegardenerTV YouTube: Building Soil for Raised Bed Gardens – The Perfect Soil Recipe
joegardener Blog: Choosing Materials for Building a Raised Bed Garden – Pros & Cons
joegardener Blog: How to Create a Productive Raised Bed Garden
joegardener Blog: Top 5 Reasons to Garden in a Raised Bed
The Complete Guide to Building Your Own Raised Beds | Free Download
joegardener Online Gardening Academy™: Popular courses on gardening fundamentals; managing pests, diseases & weeds; seed starting and more.
joegardener Online Gardening Academy Organic Vegetable Gardening: My new premium online course. The course is designed to be a comprehensive guide to starting, growing, nurturing and harvesting your favorite vegetables, no matter what you love to eat, no matter where you live, no matter your level of gardening experience.
joegardener Online Gardening Academy Master Seed Starting: Everything you need to know to start your own plants from seed — indoors and out.
joegardener Online Gardening Academy Beginning Gardener Fundamentals: Essential principles to know to create a thriving garden.
joegardener Online Gardening Academy Growing Epic Tomatoes: Learn how to grow epic tomatoes with Joe Lamp’l and Craig LeHoullier.
joegardener Online Gardening Academy Master Pests, Diseases & Weeds: Learn the proactive steps to take to manage pests, diseases and weeds for a more successful garden with a lot less frustration. Just $47 for lifetime access!
joegardener Online Gardening Academy Perfect Soil Recipe Master Class: Learn how to create the perfect soil environment for thriving plants.
Copper Migration From Treated Wood Garden Boxes Into Soil and Vegetable Biomass Part I: The First Two Growing Seasons After Installation | By Gerald Presley and Matt Konkler | Oregon State University
Disclosure: As an Amazon Associate, I earn from qualifying purchases. I receive a commission every time you purchase a product through an Amazon affiliate link. Some product links in this guide are affiliate links. However, none of the prices of these resources have been increased to compensate us, and compensation is not an influencing factor on their inclusion here. The selection of all items featured in this post and podcast was based solely on merit and in no way influenced by any affiliate or financial incentive, or contractual relationship. At the time of this writing, Joe Lamp’l has professional relationships with the following companies who may have products included in this post and podcast: Milorganite, Soil3, Territorial Seed Company, Cool Springs Press / Quarto Group and Dramm. These companies are either Brand Partners of joegardener.com and/or advertise on our website. However, we receive no additional compensation from the sales or promotion of their product through this guide. The inclusion of any products mentioned within this post is entirely independent and exclusive of any relationship.
