Cinder Block Gardening Ideas – Tips On Using Cinder Blocks For Garden Beds
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By: Liz Baessler
Are you planning on making a raised bed? There are a lot of options when it comes to the material used to build a raised bed border. Wood is a common choice. Bricks and stones are good options, too. But if you want something cheap and attractive that’s not going to go anywhere, you can’t do better than cinder blocks. Keep reading to learn more about raised garden beds made from concrete blocks.
How to Make a Cinder Block Garden
Using cinder blocks for garden beds is especially nice because you can so easily pick your height. Do you want a bed close to the ground? Just do one layer. Want your plants higher and easier to reach? Go for two or three layers.
If you do more than one layer, make sure to place it so that the joints between the blocks in the second layer sit over the middle of the blocks in the first layer, just like in a brick wall. This will make the bed much sturdier and less likely to fall.
Stack the blocks so the holes are facing up too. This way you can fill the holes with soil and expand your growing space.
To make the bed even stronger, push a length of rebar down through the holes on each corner. Using a sledgehammer, pound the rebar down into the ground until the top is level with the top of the cinderblocks. This should keep the bed from sliding around. One in each corner should be enough when using cinder blocks for garden beds, but you can always add more if you’re worried.
Dangers of Cinder Block Gardening
If you search online for cinder block gardening ideas, about half of the results are going to be warnings that you’ll contaminate your vegetables and poison yourself. Is there any truth in this? Just a little.
The confusion stems from the name. Once upon a time cinder blocks were made of a material called “fly ash,” a byproduct of burning coal that can be harmful to your health. Cinder blocks haven’t been mass produced with fly ash in the U.S. for 50 years, though. The cinder blocks that you buy in the store today are actually concrete blocks and totally safe.
Unless you’re using antique cinder blocks, there should be no reason to worry, especially when cinder block gardening for vegetables.
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Read more about Starting a Garden
15 Easy Cinder Block Raised Bed Ideas
Find the limitless ways to build a garden, and one of the best is a cinder block raised bed. The cinder blocks raised garden beds made with concrete and concrete hold many benefits over metal or even with wood materials. The iron will rot, and wood will decay in the soil, maybe after a long time. However, the cinder blocks’ story is interesting as they will not decay or rot ever. Go with these 15 easy cinder block garden ideas, and build the lovely and true designs of raised garden beds, which will be quick to put together. The cinder block garden will give you so many different design possibilities and potting options as well. You can directly start growing vegetables and herbs and even the flowers in the cinder blocks, rather than using the big inside space.
For amazing design inspirations, check out these 15 best free cinder block garden ideas that will make it easier even for a beginner to plan and build a raised vegetable bed. The 8”x8”x16” cinder blocks will rock for most of these projects. Adding these square or rectangular designs of raised garden beds in your garden will surely make the map of your garden much visually pleasing.
Built-In Raised Beds
When making a raised bed instead of going in-ground, you can place it where the sun or shade is the best for the plants you want to cultivate. You can also prevent tunneling pests from decimating your plants. Plants can be healthier and more productive in a raised bed because you can control the quality of the soil and water drainage. If you build the sides wide enough to make a bench, you can even sit and garden. For those with back problems, that makes it easier to tend the plants.
DIY Raised Bed Using Concrete Blocks
Happy Weekend Everyone! I’ve been working in my vegetable garden getting my raised beds ready for planting. My raised beds are made out of wood (here’s my post on how to build a raised bed with wood), but I thought some of you might like a tutorial on how to make a raised bed out of concrete blocks. This tutorial is from Retro Ranch Revival and is part of my DIY Saturday Series where I share helpful tutorials and ideas that I find.
I had a few raised beds made out of concrete blocks a few years back and they worked really well. Some of you may remember that I had a pumpkin that started growing in an empty hole in a block and I had a square pumpkin that year!
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It’s pretty easy to make a raised bed with cinder blocks. I don’t think it’s less expensive than making one with wood, but I did find it easier.
How To Make A Raised Bed From Cinder Blocks
- Just be sure to decided on your concrete block raised bed garden design before your start – you don’t want to have to move those concrete blocks more than you have to!
- If you plan on building more than one raised bed, be sure that you leave space in between the beds so that you’re comfortable working in your garden
- Soil is always very important in vegetable gardening, even more so when you use a raised bed (which is essential a very large container). Get the best soil that you can afford. I like this one –Raised Bed Soil.
- Raised beds are great for the Square Foot Gardening Technique.. I have a free Square Foot Garden Planner Printer to help you design your vegetable garden.
See the very detailed tutorial at Retro Ranch Revamp on how they made a raised bed from concrete blocks
You may also be interested in this video on the pros and cons concrete garden beds:
Are cinder blocks OK for vegetable gardens? Answers to that & other soil safety questions
Is it safe to use cinder blocks in a raised bed, or might chemicals from the concrete blocks leach out of the blocks to contaminate your soil and food plants you grow there?
Can you use pressure treated lumber?
Can you grow food plants in the hellstrip, the area between the street and sidewalk?
John Farfaglia, extension educator with Cornell Cooperative Extension in Niagara County, responded to my questions on soil safety.
Cinder blocks in raised vegetable bed
I have seen warnings on the Internet that cinder blocks or concrete blocks used in a garden might leach harmful chemicals into the soil and ultimately into your food plants.
After doing some research, Farfaglia’s short answer was: “I doubt whether there is any issue to worry about.”
He found universities recommending the use of concrete blocks in container gardens or raised beds.
The concern cited in many warnings is specifically fly ash, the residue you get from burning coal, that might have been used in older cinder blocks, but he doubts whether that is commonly used anymore.
However, one thing you should take into consideration when using old bricks, old concrete blocks or other recycled material is where those materials came from, he said. The materials may have been resting in soil that was contaminated with chemicals. If you’re going to use bricks for pathways, pressure washing the materials should be sufficient. If you’re using materials for a vegetable garden, you would want to be more cautious.
If you’re unsure of the source of used materials, he recommends using new material.
UPDATE (8/13/2018): A reader left a comment, saying:
“Connie, you and Farfaglia are wrong – fly ash is still used in manufacturing ‘cinder’ blocks, sometimes. If you go to this product page at home depot for a 16 in. x 8 in. x 6 in. Concrete Block https://www.homedepot.com/p/16-in-x-8-in-x-6-in-Concrete-Block-30163601/100350201 and look at the question answer section, you will see that a customer asked: ‘Is there any fly ash in these concrete blocks? If so, how much?’
“The manufacturer responded with: ‘It may sometimes be included in the mixture. Fly ash is a recycled green product and is requested from some builders because they have green criteria they would like to meet – LEED certification, reduce CO2 emissions, etc.’
“I take that to mean that sometimes they have to put fly ash in a batch because it is requested by a builder, and to keep costs down, assuming the builder does not want to buy the whole batch, they have to sell the remainder to home depot and other retailers so the block you buy at a retailer like home depot might have fly ash in it.
“So yes, modern day ‘cinder’ block might have fly ash in it.”
John Farfaglia looked into this more and said that there probably needs to be more research on this. There aren’t any studies to show whether the heavy metals that may be contained in cinder blocks or concrete blocks can leach into the soil. If you are concerned, you could get your soil tested for heavy metals.
Naturally rot-resistant wood like cedar or redwood is the best choice for raised bed construction for gardeners that have concerns regarding any possibility of exposure of chemicals in the building materials.
Farfaglia also sent along information from the University of Maryland Extension: Cement block, cinder block and concrete block all are made with cement and fine aggregates such as sand or small stones. Fly ash is also often included. Fly ash is a byproduct of burning coal and so contains heavy metals and other hazardous waste. Labels do not give specific information on exactly what aggregate is used in the manufacture of the block. There is also little research data on this topic. Ultimately, this becomes a personal choice based on your comfort level. If you plan to use block as a raised bed material — and many people do – and you are concerned about potential risks, you could seal the blocks with polymer paint. Or you can choose to use another material.
(Polymer paint is latex paint or acrylic paint.)
Pressure treated lumber in raised vegetable bed
Farfaglia said people often ask about using treated lumber for raised beds. At one time, arsenic was used in treated lumber, but isn’t any longer, he said. The risk of using new treated lumber is low, but he still recommends using natural wood such as cedar to be safe.
Line a raised bed to protect against potential leaching
As added protection, when growing food in a raised bed, you can line the bed with plastic to act as a barrier from any chemicals that might leach into the soil from the building materials. Use a thick gauge plastic, like 6 mil, Farfaglia said.
Hellstrip not best option for food plants
Awhile back, we told you about one local gardener who plants herbs in her hellstrip, the area between the road and sidewalk, but a reader commented that he would be wary of eating food planted there.
I asked Farfaglia about it, and he cautions against it.
“In a lot of cases the risk is not high, but as a general practice, save that strip for ornamental plants,” he said.
That area can contain residues from salt and other chemicals used on the road, and there may be a higher concentration of lead still there from auto exhaust.
You should also be wary of beds near the foundation of an older home that may be contaminated with lead from paint that flaked off and accumulated in the soil, he noted.
If your soil is contaminated, rinsing your herbs or vegetables might not be enough to get rid of the contamination. How big the risk is depends on many factors, including how high the concentration of the contaminant is, how often you eat the food and how you cook it.
You can get soil tested
If you’re concerned about your soil being contaminated, you can get your soil tested at the Cornell Nutrient Analysis Laboratory. It costs between $50 and $150, with some tests cost extra.
More raised garden beds
Need some more inspiration? Here are a few creative raised garden beds made with logs, wood slats, concrete, cinder blocks, railroad ties, and more!
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How To Build A Raised Bed With Concrete Blocks
I built my first raised bed from concrete blocks (aka cinder blocks) a few years ago, though my garden wasn’t too successful because our yard had become much shadier. But now that we moved, I have a big empty yard that gets lots of sun!
You might be wondering about the blocks, since chances are most raised beds you’ve seen were made of wood. I didn’t like the wood idea for a variety of reasons.
- treated lumber has poison in it, and I don’t care how safe or how little gets into the food. I don’t want poison around my vegetables. Better safe than sorry.
- lumber rots.
- lumber has to be nailed/bolted/etc. together.
- lumber has to be cut to size.
- once you make your garden box, that’s the size of your box.
So I thought about suitable alternatives. Some people do freeform beds without any supports. Just pile up the dirt and organic matter and start planting. Some use old tires. Some go fancy and get landscaping rocks or bricks. I decided to go cheap and ugly with regular cement blocks. Standard 8″x8″x16″ masonry blocks, which I got at Menards for about $1 a piece.
- no chemical leaching.
- no nails, no cutting.
- they last forever.
- even cooler, if I decide to expand beds, change their shape, move them, or make them smaller, I just move the bricks one by one.
Did I mention they’re cheap?
But hey, you can use whatever you want to make your raised beds. Just adapt these instructions to fit your needs!
Here’s a quick photo of the back yard, in it’s not-quite-spring-yet, grey and scraggly state:
Raised beds should be no more than 3-4′ wide so you can reach the whole bed from either side. I grabbed some scrap paper and a pencil and drew up some diagrams. Originally I was going to do a few loooooong beds that were 4′ by 20′. But I soon realized that I could assemble and fill a bed that was 4’x10′ much faster, and thus I could start planting sooner.
1. Lay out your blocks in the bed size of your choice.
2. If your bed is in the middle of your lawn, like mine, we need some sort of grass removal system. Instead of removing the sod with chemicals or back breaking labor, we’re going to smother it. Some people use a couple layers of newspaper, but I prefer cardboard.
You want brown corrugated cardboard without too much printing on it. No glossy cardboard. Avoid white cardboard, as it’s been bleached and can leak chemicals into the soil. Same with heavily printed cardboard.
Remove as much of the staples, tape, etc as you can and then lay the cardboard down in a single layer in your bed.
(As you’ll see below, I’ve extended the cardboard in a 3 foot radius around my bed for a walkway. Trying to mow against the bricks is a pain.)
Another bonus is that worms love newspaper/cardboard. And worms mean good soil.
3. Get the cardboard sopping, soaking wet.
For the walkways, cover the cardboard with mulch. I use a cedar bark mulch. Whatever is cheapest. Don’t be stingy with the mulch. You want a good 4-6 inches of mulch at the minimum. It will compress a lot over time, and you’ll add to it as needed.
4. Fill the bed with your planting mix of choice. I’m using the Square Foot Gardening method, which is a way to maximize the amount of vegetables you can grow in a small space. Because you’re planting closer than you would with traditional rows, you have to use a high nutrient mix, which is actually soil-less.
The recipe for Mel’s Mix is 1/3 compost, 1/3 peat, 1/3 vermiculite. (Mel is the creator of Square Foot Gardening.) The compost should be a mix of 5 different types. I wound up with 4… close enough.
In small batches, I dumped equal parts of my 3 components onto a tarp and then by picking up different ends of the tarp and flipping the ingredients around was able to mix it up fairly quickly and then dump it into the bed.
5. AFTER your seeds have germinated and established themselves (or after you’ve planted plants, if you go that route), layer mulch on top of your raised bed. I put the mulch on mine before I planted and wound up taking it off. It’s just too much of a pain to try to plant THROUGH the mulch.
Note: The calculator said I needed 30 cubic feet of mix to fill my bed. I wound up filling my bed with 20, which left the perfect amount of room on top for mulch.
If you’re not sure about mulch, read a little about the Ruth Stout system. No tilling, no weeding, less watering? Sign me up.
Here’s my finished bed! Note the color of the grass… I completed this bed quite a while after I started it. After all the rain, the grass is MUCH greener.
There were a few spots of grass poking up around my walkway. No worries- just grab a big handful of mulch and dump it on top. Keep on top of that and you’ll have gotten rid of the grass with ALMOST no work.
You can see where I’ve marked my 1 foot columns with string. I still need to mark the rows, but it was enough to get my first few squares of seeds in the ground!
I planted peas, broccoli, lettuce, swiss chard, beets, and carrots. I can’t wait to EAT THEM.
Hopefully I will beat the rabbits to the goodies. I was absolutely committed to fencing the vegetable garden, but now I’m thinking I might be able to get away with using a couple other methods to keep them away.
My neighbor has an unfenced veggie garden and she uses aluminum pie plates as a scare tactic. They’re pretty loud when they blow in the wind… they scared me until I figured out what the noise was. I think that combined with sprinkling hair clippings in the yard (they avoid the smell of people) might be enough. Famous last words.
8 thoughts on “ How To Build A Raised Bed With Concrete Blocks ”
Your just right to avoid wood this time, we made our raised beds with wood had massive slug problem, then I saw a gardening tip sayin place a piece of wood in the garden to catch slugs had a look and there was like a colony of slugs living it up on the wooden sides of the bed. Greatfor them not so great for us! Urghhhhh! Looks like your new space is lovely and sunny x
Yuck! I am having an earwig problem right now, myself. Some very disgusting creatures inhabit our gardens. And I wouldn’t even mind them if they weren’t so destructive!
Thank you so much for your step by step plan of how to do this. I have a lot of roots in the yard, so I feel the best way to have a garden is to use the raised bed method. This looks the easiest for me to do, and not too expensive. I have been composting for about 2 yrs so I have so good starter soil. I have brown boxes from work, so I think I’m set!
Really it is a nice post of gardening. Here it nicely describing soil preparation before plantation. I am so pleased to go through a wonderful article. Thanks for sharing so essential content….
Thanks for sharing this!I’ve been wanting to do this for a while now!
What types of compost did you use? I’m not entirely sure what to look for.
I did a combination of mushroom compost, chicken poop (chickity doo doo brand), and something that was really generic-sounding like “organic compost.” I went with a blend instead of just getting the “plain old” compost because I read some people saying that you don’t really know how much quality organic matter you’re getting with that stuff, whereas the mushroom compost and chicken poo are more specific.
Never thought that carboard is very beneficial when building a raised bed with concrete blocks! Thank you for sharing this article!
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Hi, I'm Lex! I’m a writer, craft addict, and former professional seamstress/fashion designer.