How to Build Above Ground Planter Along a Fence Line

This is an item I undertook after 16 years (or so) of looking at the stupid side yard on the left side of our house. It’s an area we go only to take out the trash, it grows really good grass, and it primarily serves as a place for our dogs to do their business unsupervised. It never occurred to me to build an above ground planter along the fence line, but it should have been a no brainer. Maybe I delayed because I knew if would be a LOT of work!

Why build an above ground planter – or four?

Where my above ground pool now sits is where our original garden sat. Our rear yard is not very large, my front yard is, but not my back yard, so flexibility is key so far as I’m concerned. In ground pool? Not enough space, but if I got creative I could have one, yet then we’re married to the yard format. Same with an in ground garden. Also, the soil here is very clay like – so things like cherry tomatoes and jalapenos grown well, corn does okay, the peach tree overachieves, but that’s it. Green peppers always stunt their growth and fall off, regular tomatoes too. Watermelon and cantaloupe do well, but then split down the middle before harvest time.

I could spend a lot of money and augment the soil, and I have done just that. But what if I could just start with great soil, and block my fence off from my dogs at the same time? And make it look good? I love multiple use ideas, so this was a winner-winner-chicken-dinner sort of idea.

It was hard work – But did you die?

No, I did not, in fact, die. I wanted to at times. Only one part was hard work. 1st of all, I have an average amount of tools that a man my age ought to have. Afterall, we don’t live in the sticks! The only power tools I used were: my relatively new DeWalt 12v drill, my Dremel, and a 1970’s era circular saw.

FYI – I bought the drill as a project for work and I honesty thought I was getting the 20v big boy model like I have in my work van. The low price should have tipped me off that is was a junior model. The Missus Drill, if you will.

Every thing else was straight manual labor. I’m not afraid of a little work, but this project – at times – had me talking to God. “Dear Lord, I’m too old for this sort of stuff, will it never end?”

The hardest part? Shoveling the 20 years rock hard sloped compacted clay-ish soil to level where the planters would sit. . That took me a couple weekends. For this I had a spade shovel, and a flat nosed shovel. Oh, and a garden hose to try and wet the soil so it would be easier to move. The thing about high clay soil is that was can soak for hours and the water may only make it 1/4 to 1/2 inch in! All dry and hard under there. Ugh.

Why So Long?

Why did it take me 16 years to do decide to build an above ground plater? Well, for starters, where our pool now sits was where our garden was located until about 6 or 7 year ago. We grew everything there, tomatoes, corn, peppers, melons, all the good stuff. Then I lost interest with the constant upkeep and let the garden get overgrown. This later became the above ground pool location.

Next to the fence – is this a good location to build an above ground planter?

In our case, it is. This is an unused area of the yard, and it gets direct sunlight most of the day.

On the left far side of our backyard is the fence with the neighbors. These neighbors bought the house next door about 8 or 9 month ago, unlike the previous owners, who lived next door for close to 19 years, so we were neighbors for over 16 years.

During those 16+ years the neighbors dogs and ours had numerous “doggie conversations” through the fence nearly every day. We have replaced and added slats to keep the dogs from seeing each other, but without fail when our dogs would instigate – or not – we were right on the situation, bringing our dogs into the house.

At one point we installed a picket fence at the back of the pool to keep our dogs away from the side yard fence, but “little One”, Pee Wee (aka Reese) soon figured out how to get around that. Eventually our long term neighbors moved away. They are very much missed! Not that there is anything wrong with the new owners/neighbors, but imagine 16 years next to the nicest people you ever met.

Why the lights and posts?

I’m a firm believer that form should follow function, but that does not mean, like, we should all be driving Pontiac Azteks, the poster child for form following function. So really, function first, then form.

The upright posts will allow us, later, to put up either small slats, or maybe clear plastic coated wires up to keep the pup out of the garden. Atop the posts are solar LED light post caps that brighten that otherwise dark area of the yard. So it’s almost like garden furniture, which happens to be filled with dirt.

How are we watering this above ground planter?

The last item is the irrigation. This side yard was piped for sprinklers before we bought the house, and has really good coverage. I’ve altered it quoited a bit over the years, adding water outlets for future expansion, installing more lines, etc. In fact this side yard, and the front yard were nearly complete so far as sprinklers when we bought the house, but it being a foreclosure all the yards were 100% dead when we bought the house.

I made a few edits to the sprinkler systems, added a new system to the right side yard, and manually tilled all the yards (by the way, never do this with The Garden Weasel – it has a lot of uses, but not tilling rock hard soil – ask me how I know!) and seeded all the grass.

The Garden Weasel – Amazon Associates Link

Back 16 years ago VERY few houses in my area had green yards, and after I planted from scratch, literally, an old retired marine named Sam move a few houses away and sodded his yard – making it gorgeous – the rest of the neighborhood started taking care of their yards. I bring this up because at the back of the lead image on this article, the last 20 feet of grass near the peach tree in the background is the left over sod Sam gave me about 15 years ago.

Back to watering the above ground planter

To water the planter, rather than rely of the small amount of overspray from my Rainbird Rotary sprinklers (amazon associates link), I tapped into the yard’s sprinkler line and ran a separate line off of that. This line feeds 4 “standpipes” that feed 4 separate 8 head manifolds for the 4 conjoined above ground planters.  The most lines I have used so far is 5 per manifold, but I have the flexibility to have 32 separate drip lines total should I so choose.

After the manifold I fed 1/4″ drip lines down to small mini sprinklers, adjustable 360 degree vortex emitters with stake, which I got on Amazon. Yep, another Amazon Associates link. Hey, these blogs don’t write themselves, and my time is costly!

These little sprinklers are almost too effective, but I can dial the water pressure down at the manifold to hep control the water, as well as adjust the throw, or distance, at the mini sprinklers themselves. And they attach to the 1/4″ drip line SO easily using a compression fitting! Slide the line in and you’re done!

How big an area is this above ground planter?

There are 4 interconnected boxes, each box is about 8′ long, and just over 2 feet wide, and about 1 foot deep. So there’s about 64 square feet of growing surface, and about  64 cubic feet of soil. That is smaller than our old garden, but it will be much easier to reach everything, making planting, harvesting, and weeding so simple! And while the rear top boards are simply 2x4s, the front trim is all 2×6 boards, making for a sturdy shelf.

I did divide each above ground planter into it’s own cell if you will. See, I’m weird, like OCD weird, and subdividing things is my default setting. You eat an elephant one bite at a time. But I kept the above ground planters as 4 planters, joined, because I built each one at a time.

Weekend one, level the soil for planter one. Second weekend, build the first above ground planter, level the next area for planter 2, then add soil to planter one. Weekend three, build planter 2, level the soil for planter 3 add soil to planter 2, and so on. But there were a lot of other items to do as well, such as sealing the wood walls of the planter before installing them.

How did you solve the wood rot issue?

As you know, if you’re going to have wood touch soil, you should use pressure treated wood. However, here in California, the big box hardware stores will not cut this sort of wood. Chemicals, don’tcha know. And I want these chemicals in the food I’m growing? Nope. So cutting all the wood myself, which I don’t have the tools for, is a no go. I can cut some of it, but the less I has to cut, the faster the work should go.

I used plain pine dimensional lumber, like you might use to build a house. But I treated the wood with a coating of wood sealer / clear stain. This is sort of like Varathane, but no one local had actual Varathane! So I used Valspar One Coat Exterior Sealer – Clear. At about $50 a can, I needed 1.10 cans (so I bought two cans!) for the 4 planters. If you build one planter, a quart (if you can find it) is almost enough.

I’ve used products like Varathane since I was a kid, near 50 years ago, and it STILL has successfully sealed my wood projects from then. This Valspar stuff has a 3 year guarantee. I’ll bet I get 5 years out of it, and then another 5 years before my raw green pine boards rot out.

Sure, the  lumber purchased at Lowes, being green and all, will warp some. At the end of the day it’s a planter, so what.

Building an above ground planter box like the one in the photos not only transforms the yard but also gives us a dedicated space for vegetables, flowers, or herbs. Down below is a shopping list and the exact steps you can follow to recreate this project.

What about keeping the dog out of the above ground planter?

This was a major concern, because the fence behind the planters, historically, is our designated doggie area. No, we did not designated it as such, but the doggos did. “Hey, neighbor, let me yell at you for no reason, to protect my humans from you standing there in your yard doing nothing.”

So, between the posts I’ll either make double swinging gates, hinged at the posts, at each planter, or perhaps a plastic coated cable fence at each planter attached to the posts. I have not decided yet, to be honest.

Above Ground Planter – 4 Joined planters – Materials List

Lumber –

• 2×6 pressure-treated boards – for side walls (stacked for depth), and for the front trim. 22 total eight foot 2×6 @ about $7.25 each. About $160.00.

• 4×4 posts – corner and mid-span supports. – The front 5 are 21.5 ” tall, the rear two are 20″ tall. Originally I planned to put posts in the rear too, but why? This above ground planter is again the fence, so there is already a barrier there. So you will need to 8′ 4x4s. I had Lowes cut mine to spec. I tried cutting them with my circular saw but could not get cuts that were even enough. Two untreated 8′ 4×4’s is about $30.00 with the additional cuts.

Additional wood for the above ground planter

• 2×4 boards (optional) – for the rear top trim rail. I planned on using 2×6’s here too, but I did not need a shelf against the fence, and I wanted to leave future service access to the sprinkler line that runs behind the above ground planters. Also the risers, I wanted to leave access for them as well. there were about $4 each, so $16.00 total.

• 6×6 wood – this was a stop gap solution – I knew I wanted a shelf edge along the front of the above ground planter, you have to set stuff down, right? I also wanted to use that shelf as a label system for what was planted, with spung clips holding either the original seed packets, or other labels. Additionally, I wanted to have posts to make lightweight fencing to keep the pup out. Lastly I wanted lights atop these posts.See, the shelves, they could overlap the Oldcastle blocks, fine, but I know that someday I will want to refurbish the planter, and I really did not want to complicate that process with a lot of disassembly. Best solution? Mount the post bases on a mount separate from the shelves. The 8′ length of the sides of the above ground planter would be the same length as the shelves, uncomplicating that part of the build. Not 6×6’s are not really 6″ x 6″. They are more like 5.5″ x 5.5″ these days.

Beyond lumber for the above ground planter

• Oldcastle Tan Concrete planter all blocks – 20 of these making up the left side and right sides of each planter. I stacked then 2 high, giving me 11 inches above of above ground planter each, and about an inch on average of excavated soil gives me 1 foot deep of great soil. As seen here. At about $4.00 each, you’re $80.00 into the project with a 4 planter set up.

• Rebar – Ten 1/2-in x 2-ft Steel #4 Rebar is what I used to secure down each 2 tall stack of the Oldcastle blocks.
• Sealant – Valspar One Coat Exterior Sealer – Clear as shown above. This will seal moisture an dirt out of the wood slats.
• Paint – I painted the fence behind the planters a chocolate brown. I had been planning on painting my wood fences for years anyway, what better time that when building the above ground planter? So, still having a little of this paint leftover, I wanted to contrast the planter wood, which when sealed have a Scandinavian look, with the same chocolate brown I use on the fences. I used the Season Flex Valspar  Flat Base 4 Tintable Latex Exterior Paint + Primer ( 1-gallon ) in the Boston Legacy brown, SKU 2005_9A. About $45 a gallon.

Attaching the Pieces

• Glue – This is for securing dowels, used to attach 6×6 post bases to the 4×4 posts, using dowels, and the post bases to the Oldcastle concrete slotted blocks. I used Gorilla Glue for the post bases to the posts and the attaching dowels. The cost was About $5.
• Construction Adhesive and caulk gun – I used Liquid Nails to secure down the post mounts, and it sort of worked. The wood to rough cinder block sort of connection will need some reinforcing. I augered the post mounts to insert a down, 5/8″, Gorilla Glued that into the mount, then pushed Liquid Nails into the cinder block holes above the pounded in rebar. This worked ok, but I thought it would a bit stronger bond. I’ll do a video on the final fix later. Oh, and you’ll need a caulk gun as well to dispense the Liquid Nail product. You’ll be out the door with this line for about $10.00.
• Dowels – I cut down a 4 foot 5/8″ round dowel to about 3″ segments and used these to help stabilize the post mount plates. These plates were 5.5″x5.5″x5.5″ (so a 6×6 cut into seven 5.5 inch chops). The plates would mount to the cinder blocks underneath, with  5/8 down augered into the wood, and glued in there, and into the cinder block center hole with construction adhesive. At the top of each block plate I drilled in 3 two inch 3/8″ around oak dowels, as well as into the posts. Glued them up, put them under compression, boom, super strong! This was about $6.50.

Foundation & Fastening

• Exterior wood screws – rust-resistant, outdoor rated. Assorted size were used, but most 3″ long self tapping strews were used primarily to attach the front shelf the the top of the planter side walls.

Soil & Growing Medium for an Above Ground Planter

• Landscape fabric (optional) – to line the bottom. I did not do this. I’m bot concerned with foreign plants coming up from the bottom, and over time the soil over a foot down will soften.

• Raised bed soil mix and compost – enough to fill the planter. – This would be 64 cubic feet for 4 planters of this size. Now, I augmented the amount of soil I needed to by dumping my lawn clippings into each above ground planter for 4 straight weeks. The upside, the grass will decompose (or compost) releasing nitrates into the soil. The downside is as the clippings decompose, the soil level drops. So, today I have a composter arriving. I’ll do a video on assembling this, and starting my composting journey. Maybe a blog article as well.

  The soil I bought was the Kellogg Fruit flower and vegetable Organic Garden soil, which comes in 3 cubic feet bags. While this is intended for in ground gardens (you mix it with your regular soil) I went a different direction. 50% of the soil was the Kellogg, 10% native clay based soil mixed in, and 40% Gardener’s topsoil, in 1 cubic foot bags. At about $3.00 a cubic foot for the gardeners (after tax) and $3.60 a cubic foot after tax for the Kellogg soil, the average is about $3.30 a cubic foot. So about $211.00 in soil.

Irrigation & Lighting

• Drip irrigation tubing with emitters and connectors – Since every yard and set up is different, I’m bot going to get really deep into this. How you have so up your watering is going to be different. As I mentioned earlier, I tapped into my left rear yard sprinkler system with a 1/2 inch branch line, fed this into 4 standpipes that leads to an adjustable 8 stations manifolds (Amazon Associates Link). From there we feed into 1/4 inch drip lines, and finally to mini-sprinklers (Amazon Associates Link). $40.00 total and up.

• Solar post cap lights – decorative and functional lighting – this is what I used, and of course I got them on Amazonn, hence the amzon Associates Link: Dynaming 6 Pack Solar Post Cap Lights Fence Post Solar Lights Fit for 4×4 5×5 6×6 Vinyl/Wooden Posts, High Brightness Warm White. For me, this makes the above ground planter as much utility as it does an outdoor feature. $40.00.

Tools

• Circular or miter saw. – I used a vintage circular saw, but I almost bought a compound miter saw for this project. I figured I would rarely use it, so I saved maybe a couple hundred dollars.

• Drill/driver with bits. Auger and bits, definitely worth having anyway.

• Level and measuring tape. Yep, used them.

• Shovels and wheelbarrow (wheelbarrow optional).

• Saw horses are a must. These are the exact ones I have had for years – Amazon Associates Link.

  

Step-by-Step Build

1. Plan and Measure

Measure the fence line where you want the planter. Mark post spacing (typically every 6–8 feet) for stability.

2. Set the Posts

• Place OldCastle blocks on the ground as footing.

• Insert your (hopefully sealed) 2×6 lumber into the notches in the blocks.

• Use a level to ensure posts are straight and aligned.

3. Frame the Base

• Attach 2×6 boards horizontally along the ground between posts using the notches.

• Continue stacking boards until you reach the desired planter depth (usually 2–3 boards high).

4. Reinforce and Align

• Add rebar by pounding it into the center holes of the OldCastle blocks.

• Install cross-bracing with 2×6s at each 8 foot span.

5. Line the Bed (Optional)

• Lay landscape fabric inside to prevent weeds and soil loss through cracks.

6. Fill With Soil

• Use a nutrient-rich soil/compost mix.

• Spread evenly and level.

7. Install Irrigation

• Run drip irrigation tubing along the bed.

• Place emitters near each plant location.

• Connect to a garden hose adapter or automatic timer. I tapped into my existing sprinkler system.

8. Add Lighting

• Cap each 4×4 post with solar lights for nighttime visibility and style.

9. Plant and Enjoy

• Add your vegetables, flowers, or herbs.

• Turn on irrigation, sit back, and admire your new above ground planter.

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